B-982 AUGUST l96l THE AGRI ULTURAL AND MECHANICAL COLLEGE OF TExAs TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS. Dmzcroa, COLLEGE Srxrxon. TEXAS In with the U. S. Departmant of Agriculture The greenbug is one oi thevrnost damaging bi grains. Losses irom reduced yields oi grain and iorage ire- 1 quently have exceeded several million dollars in a single season. Because oi the expense oi presently available controls and the comparative low per-acre value oi small grains. the develop- ment oi greenbug-resistant varieties oiiers the most economical and practical means oi controlling this pest. Studies on green- bug resistance in barley. oats and wheat were initiated at Sub- station No. 6. Denton. Texas. in 1951. Results oi these studies through 1959 are presented in this bulletin. All oi the testing ior greenbug resistance was done in a controlled-environment insectary. The insectary and testing technique are described. More than 18.860 varieties and strains oi barley. oats and wheat oi domestic and local origin. irom hy- brids and collections oi the U. S. Department oi Agriculture. have been tested ior greenbug resistance during this period. Iniormation on those having significant resistance and which may be oi use to plant breeders is presented. Greenbug resistance oi significance was iound first in Omugi. Kearney and several other varieties oi barley. It was transferred to desirable domestic varieties by crossing. Several resistant strains selected from these hybrids and oi potentially economic value have been included in state yield trials and in the U. S. winter barley nursery. and numerous strains irom other crosses are being tested. Studies on the inheritance oi green- bug resistance in barley indicate that a single gene is involved. Spring and winter-type collections oi the U. S. Department oi Agriculture have been screened for additional resistant germ plasm. and several varieties with resistance equal to or greater than that oi Omugi were iound. These are being incorporated into the breeding program in Texas. Several oat varieties with significant resistance were iound ior the first time when the USDA world oat collection was screened ior greenbug resistance. It is being transierred to do- mestic varieties through a breeding program at the Denton sta- tion. This breeding program has not been in progress long enough to indicate the successiul development oi adapted re- sistant oat strains. Several greenbug-resistant wheats which had been screened from the USDA world wheat collection at Stillwater. Oklahoma. have been crossed with domestic varieties at Denton. However. the resistant parents oi the crosses are spring-type wheats and oi poor quality. so much more breeding work will be necessary before acceptable greenbug-resistant dvarieties ‘will. be available ~ to hard red winter wheat-e growers. y Studies on evhiheritancef _ oi greenbug resistansie ihat ‘atsxngle ‘ 1t gene is involved. _althat1g_ certain genetic backgraundsi H CONTENTS Summary......................._..~ Introduction...................... Review oi Literature . . . . . . . . . . . . Materials and Methods . . . . . . . . . I l The Insectary . . . . . . Greenbug Source . . . . . . . . . . . . . Source oi Small-grain Varieties Screening and Rating Varietiesé Plant-longevity Tests . . . . . . . . . .. Antibiosis Tests............... Experimental Results . . . . . . . . . . Barley........................: Wheat....................... Field Tests Discussion....................... Acknowledgments . . . . . . . . . . . . .. l Literature Cited................ Breenhug-resislance Studies with Small Grains H. L. Charla, I. M. Atkins, J. H. Gardenhire and 1]. E. Weibel* HE GREENBUG (Toxoptem graminum (Rond.) ), among several aphids that attack small grains, is one of the most damaging insects of small- grain crops in the United States. Fifteen serious outbreaks have oc- curred since 1882, l0 involving parts of Texas. Estimated losses from reduced yields of grain and forage or total destruction of crops frequently have exceeded several million dollars in a single season. The greenbug can be controlled by modern insecticidal sprays, but often these are impractical or are not effective because of weather conditions. Where grain yields are low, as frequently occurs in the low-rainfall, wheat-producing areas of the Midwest, the costs of insecti- cidal controls often are prohibitive. Many 0f these products are very toxic and must be used carefully where the small-grain crop is grazed or harvested for feed of any type. Most of these insecticides are not highly effective at temperatures be- low 50° F., but greenbugs feed and reproduce normally at such tem- peratures. Parasites and predators of the greenbug are relatively slow in development at temperatures of 50° or below. Temperatures in many seasons and locations, there- fore, often are unfavorable for con- trol by chemicals 0r natural ene- mies. Cultural control practices *Respectively entomologist, Entomology Research Division, Agricultural Research Service, U.S. Department of Agriculture, Oklahoma State University, Stillwater, Oklahoma (formerly at Denton, Texas); agronomist in charge of small grain re- search, Texas Agricultural Experiment Station and Crops Research Division, ARS, USDA, College Station, Texas; agronomist, Substation No. 6, Texas Agricultural Experiment Station, Denton, Texas; and formerly research agronomist, Crops Research Division, ARS, USDA, now at Oklahoma State University, Still- water, Oklahoma. have some influence on greenbug populations, but often are not ade- quate. For these reasons, better measures are needed for a low- value crop such as small grains. Greenbug-resistant varieties offer the most economical and practical means of control. Resistant varie- ties have been used against the hessian fly (Phytophaga destructor (Say)), and against several other insects. Such varieties may not be immune from attack, but insect populations increase on them more slowly; therefore, they are more readily controlled with chemicals when necessary. Greenbug-resistance studies were initiated at Substation No. 6, Den- ton, Texas, in 1951. These investi- gations included: extensive screen- ing of the domestic and U. S. De- partment of Agriculture world col- lection of small-grain varieties and hybrid lines in a search for resistant germ plasm; the testing of early generation lines from hybrids be- tween commercial and greenbug- resistant varieties; studies of the in- heritance of greenbug resistance in wheat and barley; and field tests of resistant varieties. More than 18,860 varieties and strains were tested. Complete records are on file with the U. S. Department of Agriculture and at the Denton station. Only those varieties and strains that showed some resistance and, therefore, are of value to other breeders or research workers are re- ported herein. REVIEW OF LITERATURE According to Hunter (18), the greenbug was described and named (Toxoptem graminum (Rond.)) by Rondani of Italy, who observed the aphid infesting grasses in 1847. Webster and Phillips (32) stated that the greenbug was first found in the United States in Virginia in 1882. These same authors reported that the first damage to wheat in Texas occurred in 1890 in Denton and nearby counties of North- central Texas. Damage to wheat and oats also was trecorded in 1901, 1903, 1904 and 1906. These in- festations were followed by the serious, widespread outbreak in 1907, when the insect damaged crops in Central Texas, then spread in a fan-shaped area extending northward through Oklahoma, Kansas, Missouri, Arkansas and into Illinois. e Less extensive outbreaks occurred in parts of Texas in 1916, 1922 and 1933, according to Bilsing (5) and Hyslop (19). A major outbreak in 1942 extended from Central Texas to Northern Oklahoma, and an esti- mated 61 million bushels of grain were destroyed. Major outbreaks occurred in 1950 and 1951 when most of the wheat in the Texas Panhandle was destroyed (14). Since effective insecticides were not available, early research work- ers, Webster and Phillips (32), Bilsing (5), Hunter (18) and White- head and Fenton (33), recom- mended crop rotations, plowing and burning of early fall infested spots, and destruction of volunteer grains as control measures. Hunter (18) was the first to observe that the hymenopteron, (Aphidius tri- tici (Cress.) ), was an important parasite, and he attempted to use this insect in biological control by spreading it in areas ahead of the advance of the greenbug. The importance of the convergent lady beetle (Hippodamia convergens and other coccinellids as predators of the greenbug and other aphids has long been recog- nized. Webster and Phillips (32) were perhaps the first t0 suggest chem- ical control. They reported that kerosene emulsion and whale-oil soap were effective on bluegrass lawns in Washington, D. C., in 1907. Dahms (12) tested many materials, but found that a para- thion spray at 0.25 pound per acre was the most effective. Several in- secticides reported by Daniels et al. (14) are now available where their cost is justified. Resistance of plants to insect at- tack has been observed for more than 150 years. Extensive reviews of references on insect resistance in more than 100 plant species are given by Snelling (28, 29) and Painter (25, 26). LePelley (20) stated that as early as 1831 George Lindley observed that the Winter Majetin apple was resistant to the woolly apple aphid (Eriosoma lanigerum (Hausm.) ). Bioletti et al. (6) also reported that certain grape stocks were resistant to the grape phylloxera (Phylloxera viti- foliae (Fitch) The economic value and biological significance of insect resistance in plants were dis- cussed by Painter (23). Differences in reaction to attack were observed first by Wadley (30), in 1931. He found that it was diffi- cult to rear greenbugs on Mindum durum wheat or Vernal emmer. On emmer, less than 10 percent of the insects matured, and no second generation developed. Fenton and’ Fisher (16) observed that barley was the preferred host and that oats and wheat followed. Varietal dif- ferences in reaction to greenbugs were observed among a large col- lection of barley, wheat and oats grown by Atkins and Dahms (4) during the 1942 outbreak. High resistance was found among barley varieties, especially certain ones of Oriental origin. A moderate re- sistance was observed in wheats; among the best were certain Mar- quillo x Oro strains, which also were resistant to the hessian fly. Varietal differences were observed among the oat strains, but no high degree of resistance was found._ It was suggested by Atkins and Dahms 4 (4) that a search be made among world sources of small grains for resistance. Later Dahms et al. (13) tested several hundred varieties and strains of oats, barley and wheat in a search for greenbug resistance. None of the oat varieties showed appreciable resistance, but among plants of Dickinson durum wheat, No. 485 (C.I. 3707) they found some with high resistance. Seed of these were increased, and this strain is now being used in breed- ing programs at several locations. More recently a second unnamed resistant variety, C.I. 9058 from Iraq, was found. Arriaga (1, 2, 3), working in Argentina, developed an insectary technique and tested small grains for resistance. He found varietal differences in barley, wheat and rye, but none in oats and concluded that the laboratory tests were superior to field trials for selecting resistant strains. Resistant rye strains have been developed and distributed to growers in Argen- tina. Silveira (27) reported differ- ences in reaction among varieties of wheat and rye in Uruguay. Some studies and observations have been made on the nature of resistance, but much more research is needed. MacLeod (21) and others stated that little is known about plant resistance to insects. Chatters and Schlehuber (8) found that resistant varieties of barley had thicker leaves, but insufficient evi- dence made these authors hesitate to conclude that this leaf character was associated with resistance. Painter (24) studied the food re- quirements necessary for growth and reproduction of greenbugs and observed that the absence or in- accessibility of any of many sub- stances might be related to resist- ance. A correlation between plant vigor and degree of injury was ob- served by Walton (31). Maxwell and Painter (22) found that the rate of honeydew deposition by greenbugs was influenced almost directly in proportion to the known resistance of the host plants. Dahms and Fenton (10) stat,_ 1939 that insect resistance in p j was inherited, but the cause complex and sometimes influe i the biology of the insect i ‘i, Studies on the inheritance of sistance to greenbugs in O barley were conducted by D et al. (13) and by Gardenhire ' Chada (17). They found that ance was conditioned by a dominant gene. Tests are in p, ress, but have not yet indicatedf linkage group involved. Inhf ance studies of resistance in a were carried out by Daniels _ Porter (15) and by Curtis ef (9). These authors report single recessive gene for resis 1 in Dickinson Sel. 28A alth there appeared to be modifie minor genes involved. Curtis 1. (9) stated that Dickinson Sel."? and C.I. 9058 appeared to hav same gene, but they were i=3," find the chromosome invoil, These studies showed that f ance can be transferred to adapted varieties by n)!’ breeding procedures or a bac A program. Such programs f progress at the Texas Station, The possibility of devel greenbug biotypes that mig tack present resistant varieti been investigated in a small, In 194s, Dahms (11) obtained mens from Oklahoma and i‘ sippi, but could find no diffe in their ability to attack va More recently, however, a st greenbugs developed in the 3i. house at lOklahoma State ti‘ sity was able to damage Dic k Sel. 28A. Tests by Wood? proved that this strain behav ferently from former strains a believed the insects of this * to be a distinct biotype. f MATERIALS AND i5 METHODS Although outbreaks of gr a; occur infrequently, they are f tential threat nearly every in the principal grain-growi if of Texas. Serious outbrea occur when summer and e _ rains assist early growth of 1.»- teer small-grain plants as hosts for the insects, and when this kind of weather is followed by a dry, cool winter, in which natural parasites and predators are below normal in activity and numbers. Therefore, the testing or screening of material in the field has not been satisfac- tory in Texas. All varieties and strains were tested in a controlled-environment insectary. Differences in reaction, then, were believed to be caused by inherent characteristics of the variety or strain under test. Com- plete details of this insectary tech- nique were described by Chada (7), but are reported briefly following for easy reference. The Insectary The insectary consists of an in- sulated room 24 x 12 feet in which a uniform temperature of 75° F. is thermostatically controlled by means of two P/l-ton refrigerated air conditioners and an electric heater (Figure 1). Fluorescent light fixtures with two 40-watt daylight and two white bulbs hang approxi- mately 12 inches above the flats on each bench and provide ample light for growing the seedlings. Arti- ficial light, supplied from 6:00 a.m. to 10:00 p.m., is controlled auto- matically with an inexpensive brooder-house timeclock. The hu- midity is n~;ot artificially controlled, but usually remains between 50 and 60 percent. Cypress flats, 221/2 x 121/2 x 31/2 inches, are used for growing the plants. Each flat accommodates 14 rows of 10 plants each. To insure a uniform stand, seed are sprouted in a germinator between wet paper toweling. Ten vigorous sprouted seed are then transferred to each row for testing (Figure 2). Seed- lin.gs are covered with 1/2 inch of sand and watered. wooden stake bears the entry number of each row. Unsterilized local soil, classified as Kirvin fine sandy loam, is used in the flats. Clay soils are not satisfactory because they are sticky Figure l. General view 0f flats, plastic cages and lights in the insectary. when wet and will not permit easy removal of the cages. Watering is done by lifting the side of the cage and inserting a perforated copper tube atttached to» a rubber hose leading from an overhead water supply. Watering from the usual hydrant supply is not satisfactory because of soil washing. A cage of cellulose nitrate plastic, 22 x 12x 10 inches, fits inside the flat to cover the plants and confine the greenbugs. Acetone is used to close the joints, and wooden. strips measuring f/lx 1/2 inch, to which the plastic is attached by staples, serve as reinforcements. An open- ing, measuring 12 x 41/2 inches, covered with 34-mesh plastic screen, is made in the top of the cage to provide ventilation. The cage is placed over the flat and pressed down into the sand to prevent entry or escape of the insects. A complete insectary testing unit is shown in Figure 3. Greenbug Source The original greenbugs used in these tests, descendants of one in- sect collected near Stillwater, Okla- homa, in 1947, were obtained in 1951 from R. G. Dahms, then located at Oklahoma State Uni- versity. Greenbugs are maintained in the insectary on culture pots of Figure 2. Placement 0f test grain seedlings of oats in flats before soil covering is added. 5 Figure 3. A complete insectary testing unit showing detail of flat and cage construction. susceptible varieties of each of the crops and are transferred to new plants as often as necessary (Figure 4). Source of Small-grain Varieties Varieties and strains of domestic and local origin were taken- from the nursery at Denton. Many hybrid lines were developed from crosses made for transferring re- sistance to locally adapted varieties of small grain. Special groups, for example, the 200 Oriental wheat varieties and the world collections of oats and barley, were obtained from the Crops Research Division, U. S. De- partment of Agriculture. The small grain varieties and strains tested for reaction to the greenbug during 1952-59 are shown in Table 1. This table does not include those strains given special tests for longevity and antibiosis or retested for different reasons. Screening and Rating Varieties Varieties to be tested, along with one resistant and one susceptible variety as checks, are grown in each flat. The flats are marked off into l4 rows and then divided length- wise as well. Ten sprouted seed of each variety are planted, five on one side of the flat in regular order, and the other five on the other side in random order. The resistant check is placed in the fifth row and the susceptible one in the tenth row. Growth in the insectary is rapid. In 1 week, the plants are 3 to 4 TABLE 1. SMALL-GRAIN VARIETIES AND STRAINS TESTED IN THE CONTROLLED-ENVIRONMENT INSECTARY, DENTON, TEXAS, 1952-59 Crop » Source Number tested Barley USDA world collection varieties _ 4,445 USDA winter growth type barley varieties 1,230 Hybrid lines involving resistant parents 4,214 Miscellaneous 121 Total tested 10,010 Oats USDA world collection varieties 4,998 Miscellaneous 107 Total tested 5,105 Wheat USDA collection of Oriental varieties 200 Hybrid lines involving resistant parents l 3,225 Miscellaneous hybrids and varieties 320 Total tested 3,745 Grand total, all crops 18,860 6 riety is expressed as a percent“ inches tall. They are then infest at the rate of five greenbugs e plant. The rating for damage is ma, 10 to 14 days after infestation. varieties are rated when plants 1 the susceptible check or 0th highly susceptible variety begin die from damage by feeding. Tp, erance ratings from 0 to 5 are bas on the percentage of leaf area dag, aged, as follows: PERCENTAGE oi LEAF AREA DAMAGED 0-10 11-20 21-40 p 41-60 .1 61-80 Beyond recovery. TOLERANCE RATING UTI-POONDh-IC The average rating of each l of the resistant check variety. variation in greenbug IQQCfiOH/Qié indicated by the average rating’; the resistant check variety, was 1 a _ served between flats. This ably was due to slight differe in the ages of greenbugs used? infesting flats. Only varieties tolerance ratings lower than T’ resistant check are saved for fur“ testing. Approximately 144 v~ ties can be tested per week the facilities available. Plant-longevity Tests Varieties which appear equal the resistant check variety in f screening tests are subjected *3 longevity tests to obtain additi, information on their value. procedure is the same as for tolerance rating tests, except greenbugs are allowed to feed multiply until most of the are killed. The flats are inspe frequently, and the longevity of‘ I; variety is expressed as a percenf of the resistant check variety. longevity test is severe for survi plants since the insects concennp on them as other plants die. Si plants of a variety frequently a high degree of tolerance andi transferred to a greenhouse toil“ duce seed. These segregat mixtures may be valuable plasm. Antibiosis Tests Resistant varieties also are tested for antibiosis by determining the rate of reproduction of a single greenbug on an individual plant. Six of each variety are planted— three in each of two 6-inch pots. When 1 week old, a single green- bug, which has not reproduced, is placed on each plant. The in- fested plant is then covered with a plastic cage measuring l0x2% inches. Counts of the progeny are made 7 days later and are compared with progeny on the resistant and susceptible check varieties. EXPERIMENTAL RESULTS Screening and testing for green- bug resistance among varieties and unnamed selections of barley, oats and wheat, together with genetic studies of resistance in barley and wheat, were carried out during 1952-59. Barley Barley is an important grain and forage crop in North-Central Texas. Observations of resistance among varieties of barley grown during the 1942 infestation indicated that an excellent opportunity existed to develop adapted varieties resistant to the greenbug. The tolerance of Smooth Awn 86 (C.I. 6268), Esaw (C.I. 4690) and Sunrise (C.I. 6272) to attack in 1942 is shown in Figure 5, and that of Malwet (C.I. 2459), Nipa (C.I. 2471), Omugi (C.I. 5144) and Sonbaku (C.I. 5151) in the same year is shown in Figure 6. These varieties survived to pro- duced grain when all surrounding varieties and strains were killed. j Screening tests made by R. G. ‘Dahms at Oklahoma State Uni- versity (13) before 1952 had shown that Omugi (C.I. 5144), Kearney (C.I. 7580) and several other varie- ties had a higher; degree of resist- ance than that found in Smooth Awn 86. A breeding program to transfer resistance to adapted varie- ties was initiated at Denton in 1952, but, since no testing facilities were available, the hybrids were Figure 4. Uniform greenbug cultures maintained in the insectary on caged barley plants grown in pots. grown in bulk. Eighteen barley hybrids were so grown and when insectary tests were started in 1953, random selections were made, screened and seed increased from resistant plants. The progenies were then rescreened in later gen- erations. Considerable difference in resistance among random selec- tions within each of the crosses was observed. Although no» genetic analysis was attempted, it appeared that the Cordova x Omugi F4 and F5 selections indicated that a single gene was involved in the inherit- ance of resistance. Calculated per- centages for resistant and suscep- tible segregates in. F4 and F5 were 56.2 and 53.1, respectively; the ob- served percentages were 58.2 and 55.3. Data on reaction in these crosses are given in Tables 2 and 3. The resistance of Cordova x Omugi hybrids, compared with that of the parent varieties, is shown in Figure 7. The greatest tolerance was found in a cross of Cordova x Tongu, and several selections from this cross have reached yield trials. Most barley in Texas is fall- sown; therefore, a search was made among 1,230 winter and inter- mediate-winter barleys for addi- tional sources of resistance. These barleys were part of the USDA world collection. Wintex (C.I. 6127), a locally adapted susceptible variety, and Omugi, one of the most resistant, were used for com- Figure 5. Survival of Smooth Awn 86, Esaw and Sunrise barleys at Denton in 1942 when surrounding varieties were killed by greenbugs. 7 TABLE 2. REACTION TO GREENBUG INFESTATION OF ADVANCED- GENERATION LINES OF BARLEY CROSSES, DENTON, 1954 Number of Average Hybrid selections tolerance tested rating Cordova x Tongu 10 2.8 Wis. Barbless x Chevron 2x Bolivia 3x Chevron 4x Trebi 4x Smooth Awn 86 15 3.2 Wintex x Esaw 2 3,5 Wis. Barbless x Chevron 2x Bolivia 3x Trebi 4x Texan 1 3.8 Wintex x Smooth Awn 86 1 3.8 Texan x Smooth Awn 86 2 4.0 Gatami x Wintex 1 4.0 Wis. Barbless x Chevron 2x Bolivia 3x Dorsett 4x Wintex 2 4.1 Texan x Sunrise 6 4.2 Purdue x Wintex 1 4.2 Purdue x Tenkow 1 4.2 Gatami x Texan 22 4.3 Wis. Barbless x Chevron 2x Bolivia 3x Chevron 4x Trebi 4x Texan a 3 4.3 Smooth Awn 86 x Wis. Barbless x Chevron 2x Bolivia 3x Dorsett 3 4.5 Wis. Barbless x Chevron 2x Bolivia 3x Dorsett 4x Texan 22 4.5 Texan x Dohadak 4 4.5 Texan x Esaw 3 4.5 Cordova x Kido 8 4.5 Missouri Early Beardless x Texan 2 4.9 Omugi (resistant check) 2.8 Wintex (susceptible check) 4.5 TABLE 3. GREENBUG RESISTANT AND SEGREGATING LINES OBTAINED FROM UNSELECTED ADVANCED-GENERATION BARLEY HYBRIDS Number of Percent Percent Hybrid Generation selections resistant segregating tested selections‘ selections“ Cordova x Omugi 4 632 24.7 33.5 Cordova x Omugi 5 204 22.3 32.8 Cordova x Omugi“ 5 1,349 48.2 38.8 Cordova x Omugi‘ 3 80 15.0 28.8 Cord6va x Omugi" 69 34.8 8.7 Cordova x Kido 5 206 1.9 0.4 Cordova x Tongu 5 69 37.7 33.3 Texan x Omugi 4 110 13.6 23.6 Texan x Omugi 5 200 19.0 40.0 Texan x Omugi‘ 105 10.5 13.3 Texan x Ludwig 4 115 14.8 5.2 Texan x Ludwig 5 175 72.0 49.1 ' Texan x Ludwig5 87 17.2 6.9 Dicktoo x S-50-2-3‘-° 3 29 0.0 20.7 Harbine x Omugi‘ 3 54 5.5 35.2 10-47-84 x Omugi“ 3 21 47.6 38.1 10-47-136 x Omugi“ 3' 71 46.5 29.6 Goliad x Baitori‘ 3 35 i 2.9 57.1 46S.7l-6-0-1-0-0-0 x Cordova“ 3 23 0.0 4.3 ‘Selections showing as much or more resistance than Omugi. ’Se1ections with resistance avera e less than Omu ', but havin at least one lant e ual g g1 g P q to or more resistant than Omugi. “Reselections. ‘Selections from spaced F2 plants. “Selections from advanced bulk populations. “S-50-2-3—Wis. Barbless x Chevron 2x Bolivia 3x Chevron x Trebi 4x Texan. '10-47-84—Missouri Early Beardless x Texan selection. “l0-47-l36—Missouri Early Beardless x Texan selection. 9468.71-6-0-1-0-0-0—“Cebada negra” selection from Argentina. 8 parison in all tests. The reacti of Wintex and Omugi to insect infestations are shown in Figuref Of the 1,230 strains tested, i_ * were found to be more resis -i_ than Omugi. Longevity, plant f jury and antibiosis tests of t' varieties and strains showed that}; were ratedlat least 1Q percent m, resistant than Omugi. The l4 1' resistant varieties are shown Table 4. Since their behavior-l the three separate tests diffei greatly and single types of ~.-fi ance may be of value to other‘ search workers, the complete rec for these 76 strains is availablef Special Report W-93, Augus I 1958, Entomology Research sion, Agricultural Research Servi U. S. Department of Agricultu i: Of the 76 varieties with ance greater than Omugi, 69 from foreign countries with from the Orient (Japan 16, f‘ 15 and China 12). Only originated in the United i, three came from Nebraska and each from Georgia, New North Dakota and Missouri. _g source of one, Abyss. Wint f unknown. Atkins and Dahms; and Dahms et al. (13) also obs‘, that most of the resistant g plasm came directly or indi "-5. from Oriental barleys. A The U. S. Department of culture world collection of spring barleys was obtained in to screen for resistant germ p) in. the controlled-environment? sectary, and 4,445 varieties strains were screened before nation of the testing progra ' the spring of 1960. As with: winter barleys, almost all off‘ spring strains were highly s tible to greenbug attack, but u. this large group 36 were f“ equal or superior to Omugi i‘ sistance. Data on these strains} given. in Table 5. Several st, were much more resistant Omugi and may offer a dive source of germ plasm useful i’? plant-breeding program. Breeding programs to d adapted greenbug-resistant - varieties are now in progr of Camellia. Andrew (C.I. 4170) Tex-as and several other states. Some strains are now included in yield trials at several locations and two were included in the USDA winter barley performance nursery in 1960. Oats Oats are an important grain and forage crop throughout North- central and Central Texas, and are grown on a much larger acreage than barley or wheat. Volunteer stands and the large acreage seeded for winter pasture provide favor- able host material for the increase ' . . . . f if . . f b _ l t. Ob Figure 6. Survival of Malwet, Nipa, Omugi and Sonbaku barley varieties t0 the O_ green ug Popu a Ions‘ s€rv_a' 1942 heavy greenbug infestation at Denton. (C) Texan, (D) May Nang, (E) Malwet, tIOIIS by Atkins and Dahms (4) 111 (F) Nipa, (G) Kashmir, (H) Omugi and (I) Sonbaku. 1945 failed to identify any varieties with a high type of resistance. Dahms et al. (l8) tested 221 do- mestic oat varieties and strains in a search for resistance, but ob- served only small differences and no high degree of resistance. The search for resistance in the present experiments started with locally adapted varieties and strains. Some 102 varieties and strains from the Denton oat nurs- ery and germ plasm collection were tested in the insectary in 1954. Camellia (C.I. 4079) was used as the check because no highly resist- ant variety was known. Data on the reaction of the 14 most resist- ant varieties and strains are given Figure 7. Reaction 0f resistant lines (center) from the cross of Cordova x Omugi _ to greenbug attack as compared with susceptible plants of Cordova and resistant plants 1n Tabk 6' Complem data are of Omugi. Omugi plants are down but still green and alive. Cordova plants are dead. available in Special Report W-57, July 1, 1955, Entomology Research Division, Agricultural Research Service, U. S. Department of Agri- culture. Most of the varieties were highly susceptible. The resistance of those varieties rating better than Camellia was not significant be- cause of the low degree of resistance and New Nortex (C.I. 3422) showed more resistance than any other varieties. Andrew was used as the resistant check in all subsequent oat tests. However, it is known from past experience in greenbug infestations that these varieties, although perhaps more tolerant than most others, do not have suffi- cient resistance to offer protection _ _ _ Figure 8. Reaction of Wintex (A and B) and Oinugi (C and D) barley; to a t9 U13 CTQP undfl" field C0nd1t10n5- 2-week greenbug infestation. B and D infested plants. 9 TABLE 4. FOURTEEN OF _THE MOST GREENBUG-RESISTANT VARIETIES AND STRAINS OF WINTER BARLEY FROM A USDA COLLECTION OF 1,230 j Resistance compared with Omugi Variety C.I. or P.I. Source (Percent) or strain number‘ _ 2 Plant Anti_ Rank Longevlty inj ury“ biosis‘ Unknown 7530 Nebraska (hyb.) 153+ 60 57 1 Suwon 3 7428 Japan 142+ 84 43 2 Shokum 5233 Korea 123+ 83 30 2 Unknown 7529 Nebraska (hyb.) 148+ 61 86 4 Aizu No.. 5 8926 Japan 132+ 7 l 86 5 Unknown 9349 China - 114+ 97 20 6 Unknown 9355 China 1 06 + 65 20 6 Suwon 31 7453 Japan 1 18+ 86 86 8 Suwon 31 7454 Japan 117+ 81 100 9 Kyo-bae 35 7418 Japan 156+ 85 129 l0 Yun-wol-yuc-kac 7458 Japan 122+ 75 1 14 l0 Chang-mang-ryuc-kao 7409 Japan 143 + 89 1 14 12 Unknown 9224 Korea 137 + 74 143 12 Suwon 15 7443 Japan 113+ 87 86 12 ‘C.I. refers to accession number of Cereal Crops Research Branch, Crops Research Divi- sion, U. S. Department of Agriculture. P.I. refers to accession number of the Plant Introduction Section, Horticultural Crops Research Branch, U. S. Department of Agriculture. '*’Based on the number of days the plants lived under infestation. “+” indicates some plants were alive at conclusion of the test. High percentages (more than 100) indicate plants lived longer than those in resistant check. “Low percentages (less than 100) indicate plants were injured less than those in resistant check. ‘Progeny of a single greenbug on an individual plant after 7 days. Low percentages (less than 100) indicate high degree of antibiosis. The USDA world oat collection of 4,998 varieties and strains was screened in 1955-56 for greenbug resistance. Andrew was grown in all flats as the resistant and Mustang (C.I. 4660) as the suscep- tible check. A total of 683 varieties appeared to have as much tolerance as Andrew and 77 were rated at least l0 percent more resistant. All others were rated as susceptible. Seventy-four of the 77 oats were subjected to plant longevity, plant injury and antibiosis tests in 1957, as described previously. When the strains were subjected to longevity tests, plants that survived longer than Andrew were saved as pos- sible sources of superior germ plasm. Many were picked up in world markets and possibly seed of some varieties were mixed. Even where growing plants indicated the varieties were pure, they could have been mixed for greenbug resistance. Where mixed reaction to greenbugs was observed in seed lots, the re- sistant plants were tranplanted to greenhouse pots and grown to maturity to obtain seed and main- 1U tain the variety. The average longevity of the variety is expressed as a percentage of the resistant check. Data on the 10 most resistant varieties and strains are given in Table 7. Complete data on the 74 oats are available in Special Report W-83, Nov. ll, 1957, Ento- mology Research Division, Agri- cultural Research Service, U. S. Department of Agriculture. The varieties and strains are arranged according to the average rank for the three categories shown. Several varieties and strains were superior to Andrew, particularly in lon- gevity. According to Painter (25), “tolerance is the basis of resistance in which the plant shows an ability to grow and reproduce itself or to repair injury to a marked degree in spite of supporting a population approximately equal to that dam- aging a susceptible host.” Most workers believe that tolerance to attack, especially as indicated by the plant-longevity test in these ex- periments, is a good index of re- sistance, because greenbug popula- tions become heavy on these to ant plants as other plants killed. Some varieties survi A even though they showed able injury after infestation for i’ days. Other varieties showing lit injury after infestation for l0 d3’ became stunted or died. Of the 74 resistant variet'i tested, 37 were from 18 states the United States and 36 from L, eign countries. The source Siberian (C.I. 1712) is not record Among foreign varieties, 12 c from Yugoslavia, 5 from Turk 4 from Argentina and 3 of Canada. Twenty-three of the l originating in the United St; were Red Rustproof or related it. Among the l0 most resis varieties and strains shown 7 Table 7, only 2 were from a United States, 3 from Yugosla; and 2 from Argentina. Since _ Red Rustproof types are grown; all these areas, they may be a g j_' source of resistant germ plasm. These tests have provided -. breeders with a source of resis N f germ plasm for use in bre resistant oats. The transfer of j resistance to adapted varieties,‘ now in progress at the Denton s__ station. Further search for ;-:_;' plasm having even greater ance is needed. Mixed varief and strains from the world c0 tion may be used to isolate si plants with superior resistance. opportunity to test the resistan i these varieties under naturalj? festations in the field has occu Wheat Wheat is grown on exte i acreages throughout the Mid ~ where greenbug outbreaks 0 occur. Because rainfall is U tively low and often poorly tributed, yields often are low j the value of the crop may A justify the use of insecticides. 1- Because many of the resist barleys had their origin inf Orient, the first search for resis germ plasm in this experiment », in wheat varieties and strai Oriental origin. Some 200 A tolerance. wheats were selected from the USDA world wheat collection and tested at Denton in 1952-53. The procedure involved growing test plants in pots, and was that de- scribed by Dahms et al. (13), except that the plants were grown in the controlled-environment insectary instead of in a greenhouse. As no resistant varieties were then known, Pawnee (C.I. 11669), an important commercial variety, was the check. Data were obtained on plant con- dition on the day check plants died, greenbug preference, tolerance, antibiosis and growth index (as shown in Table 8). Most of the 200 wheats were susceptible, but sev- eral were superior to Pawnee in Because they did not appear to offer promise as sources of resistant germ, plasm, most of them are not listed. Complete data are available as Special Report W-31, April 22, 1954, Entomology Research Division, Agricultural Re- search Service, U. S. Department of Agriculture. A few of the more tolerant wheats are listed in Table 8. Although these wheats perhaps do not have high resistance, they may be of value for special studies, or resistant plants might be selected from them. A second group of 120 Oriental wheats, ranging from C.I. 9370 to 9574 (some numbers omitted), were tested in comparison with Denton (C.I. 8265), a Mediterranean strain. Denton and certain other Mediter- ranean strains showed moderate tolerance in 1942, as shown in Figure 9. Although several showed slightly more resistance than Den- ton in these tests, none is considered to have sufficient tolerance to pro- tect the crop. “After the discovery by Dahms et all (l3) of greenbug resistance in Dickinson Sel. 28A, a selection from Dickinson No. 485 (C.I. 3707) durum wheat, it was used exten- sively in breeding programs in Texas, Oklahomai and Kansas. Dickinson Sel. 28A and other re- sistant wheats were damaged se- verely in 1957 by a culture of greenbugs which developed in the greenhouse at Stillwater, Okla- homa. These same wheats were tested at Denton with the greenbug culture used there since 1951. They maintained the same resistance ob- served previously, as shown in Table 9. Wood (34) later proved that the Stillwater culture differed in size as well as ability to attack and damage formerly resistant wheats and that they constituted a biotype of the greenbug. The find- ing of the biotype by Wood empha- sizes the need for several sources of greenbug resistance in wheat and _ other small grains; otherwise, the development of biotypes could nullify many years of breeding re- sistant varieties. Wadley (30) reported in 1931 that greenbugs reared on Mindum (C.I. 5296) and Vernal emmer did not reproduce normally. A test was conducted in 1956 to determine whether certain tetraploid wheats were resistant to present greenbug cultures. Five varieties of durum wheat and Vernal emmer were com- pared with susceptible Pawnee, re- sistant Dickinson Sel. 28A and C.I. 9058. All proved to be susceptible, as shown in Table l0. TABLE 5. THIRTY-SIX VARIETIES AND STRAINS OF BARLEY SHOWING HIGHEST RESISTANCE TO THE GREENBUG FROM 4,445 OF THE USDA BARLEY WORLD COLLECTION Resistance compared with Omugi Variety C.I. or Percent of or P.I. Source Average . f strain number rating mung 91 Omugi Nigrum 2338 Engeldow 1.9 64 4015 Russia 2.2 55 4205 China 2.2 71 3982-2 Vavilov 2.4 81 8778 Turkey 2.5 83 4395 Manchuria 2.7 87 4994 Iraq 2.8 88 4015-1 Russia 2.9 72 3979-2 Vavilov 2.9 81 Chinerme 1079 China 3.0 36 4010-1 Russia 3.0 75 9827 Ethiopia 3.0 77 4150 Afghanistan 3.0 77 6992 Iran 3 0 77 4001-1 Russia 3.0 79 10145 India 1.0 83 6582 Afghanistan 3.0 89 4012-2 Russia 3 1 78 3982-3 Vavilov 3 l 85 Dubas 1460 Mesopotamia 3.1 89 3991-1 Vavilov 3.2 84 White Gatami 920 Manchuria 3.2 87 7769 India 3.2 87 Bano 2472 China 3.2 87 3985-1 Vavilov 3.2 89 9062 India 3.2 89 3980-1 Vavilov 3 2 90 6657 Iran 3.3 82 9941 Ethiopia 3.4 74 6319 Afghanistan 3.4 85 6322 Afghanistan 3.5 88 4168 Afghanistan l 3.5 90 Scarab 995 Russia 3 6 72 6658 Iran 3 6 90 7774 India 3 7 84 7604 India 3.7 89 Omugi 5144 (resistant check) 3.4’ Wintex 6127 (susceptible check) 4.5“ ‘Low percentages (less than 100) indicate plants more resistant than Omugi. zAverage rating of 3,574 Omugi plants in the test. aAverage rating of 3,511 Wintex plants in the test. ll Figure 9. Survival of Denton (C.I. 8265), a Mediterranean strain, as compared with other commercial wheat varieties during the greenbug infestation of 1942 at Denton. TABLE 6. FOURTEEN MOST GREENBUG-RESISTANT OATS AMONG 102 LOCAL AND DOMESTIC VARIETIES AND STRAINS TESTED AT DENTON, 1955 Resistance compared with Camellia Variety or strain Cglégllbféls’ Aveljage Ilirtclzflrétozf ‘atmg Camellia Andrew 4170 v 2.5 62 New Nortex 3422 2.7 90 Texas Red Rustproof T.S. 1118-69 3.0 100 Appler Rustproof 1815 3.0 100 Ferguson 71 844 3.0 100 Ferguson 922 2150 3.0 100 Texas Red Rustproof T.S. 6217-43 3.2 i 107 Texas Red Rustproof 953 3.3 89 Klein 693 W 1957 4118 3.3 92 Georgia Red Rustproof 233 3.4 114 Texas Red Rustproof T.S. 2805-43 3.4 114 Ferguson 392 1038 3.5 108 Nortex 2382 3.5 117 Texas Red Rustproof T.S. 1415-12 3.8 125 Camellia (check) 4079 3.0 ‘T.S. refers to Texas Selection. TABLE 7. TEN MOST GREENBUG-RESISTANT OATS AMONG 4,998 VARIETIES AND STRAINS OF THE USDA WORLD COLLECTION Resistance compared with Andrew . C.I. or ercent Vasrtlfglnor P.I. Source (P Pl i A _ Rank numbfll mngevityz injtziilya bidlstih“ Unknown 183992 Yugoslavia 171+ 46 83 1 Avena Selecta M.C. 41374 I.F. 186270 Argentina 138+ . 65 50 2 Unknown 183990 Yugoslavia 143+ 76 33 3 7505-43 C.I. 5608 186609 Brazil 186+ 84 50 4 Russian No. 77 2898 Canada 129+ 66 67 5 Unknown 183-991 Yugoslavia 157+ 52 150 6 Unknown 190584 Argentina 152+ 85 ' 17 7 (Bond-Rainbow) x (Hajira-Joanette) 5945 Minnesota 143+ 82 17 8 Unknown 177788 Turkey 157+ 86 67 9 Bonda x Sante Fe Sel. No. 3692-4 6443 Idaho 119+ ._ 65 67 10 1' 2* 3' ‘See footnotes to Table 4. 12 A collection of 111 wheats i had shown resistance in tests. Stillwater, Oklahoma, was reti‘ at Denton in 1958. These compared with the resistant D inson Sel. 28A for longevity, injury and antibiosis. Detaif data on all strains are on file are not given here. The rati__ and composite rank“ of the ll m° resistant are given in Table Several appear to have consideraj promise as additional sources :1 resistance in wheat. Several res ant plants from certain lines transferred to the greenhouse, high temperatures in late sp prevented maturity of the Since the present known green resistance in wheats is not as as desired, and was threatened? 1958 by the development of a v; type of the greenbug that was a2 to destroy Dickinson Sel. 28A C.I. 9058, it appears that these wheats, and perhaps the most sistant strains from other screen‘ tests, should be screened thorou ' ly for possible resistant plants. Genetic studies on the inh; ance of greenbug resistance wheat were started in 1954. l, four crosses shown in Table were made in the greenhouse Dickinson Sel. 28A and Hi (C.I. 11059). Two advanced set, tions from Cimarron hybrids i an F1 of Kansas 7088 x Red C were used. Five seed from each three crosses, X502, X503 and X i; involving Dickinson Sel. 28A, sent to Aberdeen, Idaho, in 1954 to be grown during the mer. Only one hybrid seed fa.‘ to produce a plant. F2 populations of individ- spaced plants and F2 bulk poi tions of three hybrids were in the field at Denton in 195 The plants appeared vigorous developed normally without" servable differences between and winter-growing types. Du, this same period, F, plants of; four crosses were grown in greenhouse and backcrossed their common wheat parents. Seed from individual F2 pl harvested from the 1955 field i. divided so that both field plantings of F3 lines and greenbug insectary tests for resistance could be made. Approximately 350 such F3 lines showed a predominance of spring- type plants in 1956. However, selection for further work was based entirely on reaction in in- sectary tests, not on plant char- acteristics. Four or five heads were selected from each F3 line which showed resistance in the insectary tests. Additional seed of F3-spacetl plants were sown and harvested for testing. A large number of F2 plants of the cross X501 involving C.I. 11059, a winter-growing type, and F3 plants of the other three crosses were grown in bulk popula- tions in the field in 1956. F, plants of backcrosses were grown in the. greenhouse during the same season. F2 backcross plants and F3 and F4 lines were grown in the field in 1957. The season was so extremely wet that diseases and lodging made the crop abnormal; thus it was im- possible to select among the 1,500 rows except on the basis of reaction to greenbugs. Four or five heads again were harvested from rows, the seed of which came from plants which showed resistance in the in- sectary, and the remainder of the plants in the rows were harvested in bulk for further insectary tests. New crosses were made in the greenhouse with C.I. 9058. Selection for agronomic type was possible in 1958 when approxi- mately 2,600 F4 and F5 rows were grown, the seed for each row being from individual heads. Only 64 rows were saved. All showed uni- formly high resistance in insectary tests, were resistant or moderately resistant to the leaf rust prevalent during the season and stood up wbn after reaching maturity. Leaf rust and speckled leaf blotch were severe. F3 backcross. plants were grown in the field “and F1 hybrids of C.I. 9058 in theigreenhouse. Seed of the 64 selections were divided in 1959 into three parts; one for College Station for ob- servations on reaction to rusts, one to Amarillo for hardiness tests and one kept at Denton for further TABLE 8. FIFTEEN MOST GREENBUG-RESISTANT WHEATS SCREENED FROM 200 ORIENTAL VARIETIES OF THE USDA WORLD COLLECTION, DENTON, 1953 Resistance compared with Pawnee (check) Variety C.I. or _ or PL Source Plant Prefer- Toler- Ant1- Growth strain number condition ence, ance, biosis, index, rating‘ percent’ percent“ percent‘ percent“ C31! 10391 Shantung 4.2 41 123 50 103 C21) 10339 Shantung 4.0 5 119 65 87 Flb 10728 Kansu 4.0 82 117 65 99 F2a 10729 Kansu 4.2 50 114 58 80 C4a 10392 Shantung 4.4 72 113 46 80 9165 Manchuria 4.7 105 111 113 21 C23 10388 Shantung 4.2 23 lll 50 70 N10a 11059 Hopei 4.2 172 110 41 92 N5a 11054 Hopei 4.0 190 108 ' 53 72 9160 Manchuria 4.7 52 108 42 65 G2b 10781 Hopei 4.2 70 107 112 49 N 10b 11060 Hopei 4.2 156 107 50 149 9163 Manchuria 4.2 52 107 29 41 E31 10671 Shansi 4.2 64 106 54 72 D3b 10510 Honan 4.6 70 106 67 80 ‘Average injury rating of test plant on day Pawnee (C.I. 11669) (check) was dead. ‘Average number of greenbugs per plant on fourth day after infestation expressed as a percentage of the number on Pawnee. Low percentages (less than 100) indicate less preference for plant. ‘Average number of days test plant lived after infestation expressed as a percentage of days for Pawnee. High percentages (more than 100) indicate more tolerance than Pawnee. ‘Average progeny of a single female greenbug after 7 days on an individual plant expressed as a percentage of the progeny on Pawnee. Low percentages (less than 100) indicate most antibiosis. 5Calculated by dividing the average increase in height of test plants after infestation by the average increase in height of noninfested check plants of same variety during the same period, and expressed as a percentage of the increase in height of Pawnee. TABLE 9. REACTION TO GREENBUGS AT DENTON OF WHEATS WHICH BECAME SUSCEPTIBLE TO GREENBUG CULTURE AT STILLWATER, OKLAHOMA Resistance compared with Dickinson Sel. 28A (Denton) Variety of selection Percent of rating Average of Dickinson Sel “mg 28A (Denton) Arabian Sel. C.I. 7261-15 (58 Stw. 15401)‘ 2.1 70 Dickinson Sel. 28A” 2,5 93 Dickinson Sel. 28A (58 G 1222-6)‘ 2.4 89 Dickinson Sel. 28A (57 G 1220-3)‘ 3.1 115 Bagdad C.I. 2202 2.7 100 Unnamed C.I. 9058 (57 G 1510)‘ 2.0 74 Unnamed C.I. 9058 (58 G 2351)‘ 2.7 100 Unnamed C.I. 7501 (58 Stw. 15403)‘ 3.8 140 Dickinson Sel. 28A (Denton) (resistant check) 2.7 Omugi barley (Stillwater) (resistant? 2.5 Wintex barley (Denton) (susceptible)“ 4.4 ‘I957 and 1958 Stw. (Stillwater-field) and G (greenhouse) selections made at Stillwater, Oklahoma. ‘1959 Stillwater seed. “Omugi and Wintex barleys included for comparison. Reaction to same greenbug culture was similar in previous years. 13 TABLE l0. REACTION OF SEVERAL TETRAPLOID WHEATS TO GREENBUG INFESTATION, 1956 Variety or selection Resistance compared with Dickinson Sel. 28A Percent of rating GI’ Avefage of Dickinson number rating seL 28A Stewart 12066 3.8 152 Carleton 12064 4.4 191 Vernal emmer 4.1 178 Vernum 12255 4.6 196 Sentry ‘ 13102 4.0 187 Dickinson Sel. 28A (resistant check) 2.3 Unnamed (resistant)‘ 9058 3.1 Pawnee (susceptib1e)‘ 11669 4.8 ‘Included for comparison. TABLE 11. MOST PROMISING GREENBUG-RESISTANT WHEATS SCREENED FROM A SELECTED GROUP OF 111 OF THE USDA WORLD COLLECTION Resistance compared with Variety Cl or Pl Dickinson Sel. 28A (percent) R k or. number‘ Source Plant Anti- an selection Longevity2 in ury3 biosis‘ Unknown 9556 China 100+ 111 40 1 Unknown 9573 China 100+ 1 18 10 2 Unknown 9058 Iraq 100+ 89 80 3 Unknown 7508 Egypt 94 101 20 4 Jenkin 5 177 Oregon 107 95 1 13 5 Unknown 10594 China 95+ 123 20 6 Unknown 7833 Ethiopia 95 + 1 1 1 80 7 White Winter 52 19 Oregon 107 90 125 8 Unknown 145720-1 Arabia 105+ 104 120 9 Odessa 5240 Oregon 107 91 138 10 Unknown 194043 Ethiopia 1 l 1 + 1 18 120 1 1 1' 2' 3' ‘See footnotes to Table 4. NTABLE 12. PEDIGREE OF CROSSES FOR GREENBUG RESISTANCE Cross no. Pedigree X501 X502 X503 X504 Hopei C.I. 11059 x [(Kd-HF-Tq x Med-Hope) x Cheyenne Sel. 274-50-1] Dickinson Sel. 28A x (Cimarron x Hope-Cheyenne Sel. 256-50-7 C.I. 13022) Dickinson Sel. 28A x [(Kd-HF-Tqx Med-Hope) x Cheyenne Sel. 274-50-1] Dickinson Sel. 28A x (Ks-7088-Red Chief F1) TABLE 13. SUMMARY OF DATA ON THE INHERITANCE OF GREENBUG RESISTANCE IN CROSS X501, HOPEI C.I. 11059 x [(KD-HF-TQ x MED-HOPE) x CIMARRON SEL. 274-50-1] variety o1. Plants in indicated resistance class Total number of generation 1 2 3 4 5 plants tested C.I. 11059 0 14 17 6 0 37 Sel. 274-50-1 0 4 18 5 6 33 F1 0 0 5 0 0 5 F2 0 36 174 106 31 347 Ratio = 9:7 (X2 — 2.6) Fa Res. 10; Seg. 88; Susc. 72 170 Ratio = 1:827 (X2 — .2) BC F1 0 4 5 0 0 9 BC F2 Res. 3; Seg. 2 5 Ratio 1:1 14 selection and testing. Crosses made to initiate a second cycle breeding. The most resistant! the 64 were crossed with mercial or promising varieties. Data obtained from the cr‘ on the inheritance of greenbug sistance (with several generati_ for each) have been‘ summari f Table 13 presents data on number X501, Hopei (C.I. 110. x [(Kd-HF-Tq x Med-Hope)‘ Cimarron Sel. 270-50-1]. C.I. ll_ was one of the Oriental wh‘; tested at Denton in 1953-54. P11 of 0.1. 11059 fell into classes 2 3, whereas Selection 274-50-1 ra g1 from 2 to 5 with more than the plants in class This i cates a low level of resistanceffp Selection 274-50-1. F1 plants w, rated intermediate, or class 3. F2 population fell largely classes 2, 3 and 4. By grou’ classes l, 2 and 3 as resistant - 4 and 5 as susceptible, the ratio; 9:7 (9 resistant and 7 suscepti, was obtained and was a plans! explanation of the resistance r action of Selection 274-50-l. indicates two genes must be to give resistance. However, C.I. 11059 was more resistant "I the F1 and F2, some other inte i tation seems possible; but test" F3 lines resulted in resistant, s gating and susceptible classes ratio of 118:7, as would be ex ' a from a 9:7 ratio of F2 plants. J generation backcross plants fell . classes 2 and 3 as might be; pected, and second-generation I cross lines also responded as pected from the two-factor 1; pothesis. l‘ Table 14 presents data on X502, Dickinson Sel. 28A x (C ron x Hope-Cheyenne, Sel. p 50-7, C.I.‘13022). Most plan’ Dickinson Sel.’ 28A were plac class 1, but for some unexpl reason a few were fully suscep =1 Plants of Sel. 256-50-7 fell lat in class 5, but some also ray from 1 to 2. Tests of F1 p“ were not obtained. F2 data, _ grouped as before, fitted a rat' s11. The F3 lines did not l:2:1 ratio since the res" classes contained too few plants, and the backcross generations showed more resistance than ex- pected. Data from cross X503, Dickinson Sel. 28A x- [(Kd-HF-Tq x Med- Hope) x Cimarron Sel. 274-50-1], are shown in Table 15. Plants of Dickinson Sel. 28A were classified largely resistant, but a few were susceptible. Plants of Sel.274-50-1 were largely susceptible, but some plants were in resistant classes, again suggesting the possibility of a low level of resistance. However, when classes l to 3 and 4 to 5 were grouped together, the data did not fit a 2-factor 9:7 ratio because too many resistant plants occurred. Nor did the data fit a 3:1 ratio because not enough resistant plants occurred. F3 lines, classified into resistant, segregating and suscep- tible groups, fitted a l:2:l ratio, and the second-generation back- cross lines fitted a 1:1 ratio. This indicated a single-factor inherit- ance ratio. Cross X504, Dickinson Sel. 28A x (Kansas 7088-Red Chief F1), also was studied and the data are pre- sented in Table 16. Red Chief was used to represent the suscep- tible parent. It gave plants in more resistant classes than might have been expected, however. The F2 data fitted neither the 9:7 nor the 3:1 ratios. F3 lines fitted the l:2:l ratio and indicated a single-factor inheritance. The resistance of C.I. 11059 was not comparable with that of Dick- inson Sel. 28A, but its resistance did contribute to resistance in the hybrid populations studied and in- dicated some dominance. FSince data from F3 lines were more critical than those from F2, the resistance of Dickinson Sel. 28A could be attributed to a single factor, although enough conflicting evidence was obtained to cast some doubt on such a simple explana- tion and to suggest the possibility of modifying genes in certain ge- netic backgrounds. Resistance ap- peared to be dominant. This finding conflicts with published TABLE 14. SUMMARY OF DATA ON THE INHERITANCE OF GREENBUG RESISTANCE IN CROSS X502, DICKINSON SEL. 28A x (CIMARRON x HOPE-CHEYENNE SEL. 256-50-7 C.I. 13022) Plants in indicated resistance class Variety or Total number of generation 1 2 3 4 5 plants tested Sel. 28A 20 2 0 l 3 26 Sel. 256-50-7 4 3 4 12 27 F: 99 34 29 16 30 208 Ratio = 3:1 (X2 —- .9) F3 lines Res. ll; Seg. 73; Susc. 40 124 BC F1 5 0 0 1 1 7 BC F2 Res. 3; Seg. 5; Susc. l. 9 reports, indicating that resistance is per plot. Climatic conditions, recessive (9, l5). The suggestion is made, however, that the methods of procedure might account for these conflicting reports. In the studies reported here, the insectary tests were allowed to proceed until a large portion of plants of the susceptible parent was killed, at which time readings were taken. If the tests had been allowed to continue, undoubtedly more of the heterozygous F2 plants would have been killed. Thus ratios indicat- ing one resistant to three suscep- tible plants in the F2 generation might have been obtained. FIELD TESTS Varieties and strains of barley, oats, and wheat that had shown resistance in previous greenbug outbreaks and in insectary tests during 1955-57 were sown in repli- cated nursery plots having four rows 5 feet long. Shortly after the plants emerged, they were infested with insectary-cultured greenbugs at the rate of approximately 10,000 principally high winds and tem- peratures, were unfavorable for survival and reproduction of the insects; therefore, no infestation occurred. Unless conditions are favorable for natural infestation in North-central Texas, difficulty will be encountered in creating infesta- tions. No data on the behavior of these small grains to field infesta- tions were obtained. Fifteen to 25 barleys ranging in reaction from susceptible to the most resistant have been seeded each season since 1954 in duplicate nursery plots at 6 to 10 locations in Texas to observe their reaction to natural greenbug infestations. Natural infestations of sufficient intensity to cause damage have not occurred in these plots; therefore, no data were obtained. The only time when the effec- tiveness of greenbug resistance has been tested in Texas was in 1949 at Iowa Park. Smooth Awn 86 was placed in all state tests immedi- ately after its tolerance was ob-_ TABLE 15. SUMMARY OF DATA ON THE INHERITANCE OF GREENBUG RESISTANCE IN CROSS X503, DICKINSON SEL. 28A x [(KD-HF-TQ x MED-HOPE) x CIMARRON SEL. 274-50-1] Plants in indicated resistance class Variety or Total number of generation 1 2 3 4 - 5 plants tested Sel. 28A 45 6 5 3 0 59 Sel. 275-50-1 0 1 12 13 33 59 F2 182 69 80 77 130 538 Ratio = 3:1 (X2 — .2) F3 lines Res. 33; Seg. 71; Susc. 41 145 Ratio = l:2:l (X2 — .9) BC F1 0 0 0 1 4 5 BC. F2 Seg. 3; Susc. 4 7 Ratio = 1:1 15 TABLE 16. SUMMARY OF DATA ON INHERITANCE OF GREENBUG RESISTANCE IN CROSS X504, DICKINSON SEL. 28A x (KANSAS 7088-RED CHIEF F1) Plants in indicated resistance class Variety or Total number of generation 1 2 3 4 5 plants tested Sel. 28A 45 2 3 0 0 50 Red Chief 0 4 l0 18 18 50 F: 177 75 122 95 119 588 Fa Res. 17; Seg. 37; Susc. 19 73 Ratio = l:2:l (X2 — .1) served in 1942. A severe infesta- tion occurred in the barley nursery at Iowa Park in 1949. Yields of Smooth Awn 86 are given in Table 17 to compare them with those of several commercial varieties. Smooth Awn 86 averaged 40.3 bushels per acre, compared with 28.4 for Wintex and only 19.6 for Reno. At other locations in 1949 and in other seasons, Smooth Awn 86 was not equal to Wintex. and Reno and was not distributed com- mercially. DISCUSSION ‘Varieties and strains of barley, oats and wheat having greenbug- resistant germ plasm have been found, and they offer opportunities for the breeding of adapted resist- ant varieties for the several growing areas of Texas. The highest re- sist-ance appears to be present in barleys. This situation might be expected since barley is the favored host. Resistant varieties and strains may develop from mixed seed as the result of natural selection over a long period when the plants are exposed to heavy infestations that exert a high degree of selection pressure. Barley is one of the oldest of cultivated food crops and has been grown for centuries in the Orient where many of the resistant varieties originated. The observations of resistance to greenbugs in barley during the 1942 infestation by Atkins and Dahms (4) provided suggested sources of resistance. The high re- sistance found in Omugi, Kearney and Dobaku was used immediately in plant-breeding programs in Texas and several other states. Greater progress has been made in developing adapted resistant barley varieties than in oats and wheat. Fortunately, these resistant barley varieties were fairly well adapted TABLE 17. COMPARISON OF GRAIN YIELDS OF GREENBUG-RESISTANT SMOOTH AWN 86 BARLEY WITH THOSE OF COMMERCIAL VARIETIES UNDER HEAVY INFESTATIONS, IOWA PARK, 1949 Variety Smooth Awn 86 , Wintex Ward Reno 16 C.I. Grain yield, number bushels per acre 6268 40.3 6127 28.4 6007 22.1 6561 19.6 Z to the Southwest, so the Li’ procedures were not very c0 " cated. Screening of the world i g lection has now furnished info t“ tion on many other sources‘, greenbug-resistant germ -._i This information should be in the breeding programs _, germ plasm from ESGVGTHl soup combined into multiple-fag’ breeding stocks, which will aid~= preventing a breakdown of r s ance owing to development greenbug biotypes. ' Sources of resistance appearf. be more limited in oats than ”_ barley and have been less ext ' sively tested. No observations i) field reactions of these varieties strains have been made to da, thus how effective their resista is under natural infestations is r, known. Several strains appear’; have considerably more tolera, than Andrew and New Nor Russian No. 77 (C.I. 2898) and -_ 183990 have been crossed to o? mercial varieties at Denton. Scr ing of the F2 generation is now? A progress. It is hoped that resis u varieties may be developed. ' Until recently, only two resis wheats had been found, Dicki 1 Sel. 28A and C.I. 9058. t have been used extensively Texas and other states. Since two wheats are spring-types ~' their grain quality inferior, y siderable difficulty has been perienced in developing hard " winter-types with resistance. v sults of tests reported in Tab, verify findings at Oklahoma University and show that some? ditional resistant germ plas Q available. However, much breeding work will be nece‘ before acceptable varieties ' greenbug resistance will be duced for Texas or the South . ‘i ‘fli ACKNOWLEDGMENTS The work reported in this bulletin was done cooperatively by the Small Grain Section, Texas Agricultural Experiment Station, and the Entomology Research and Crops Research Divisions, Agricultural Research Service, U. S. Department of Agriculture. Use of facilities and personnel at Substation No. 6, Denton, Texas, in connection with this work is acknowledged. The authors also thank David Ward and C. Craddock for their cooperation in supplying small-grain world collections of the U. S. Department of Agriculture. 17 LITERATURE crrEn 17. Arriaga, Hector O. 1949. Obtencion de Centenos Resis- tentes a la saliva toxica de Schizaphis graminum (Rond.) Blanchard. Ministerio de Educacion Univ. Nac. de 1a Plata Fac. de Agron. Laboratoria de Zool. Agricola B01. N0. 11: 39-47. Arriaga, Hector O. 1954. Resistencia a 1a Toxemia de Schizaphis graminum (Rond.) en cereales finos. Univ. Nac. de Eva Peron, Rev. de 1a Fac. Agron. (Tercera Epoca) XXX (1): 65-101. - Arriaga, Hector O. 1956. E1 Centeno “Insave F. A.” Hibrido sintetico resistente a la toxemia del “pulgon verde de los cerea1es.” Univ. Nac. de 1a Plata, Rev. Fac. Agron. (Tercera Epoca), t. XXXII (2a): 191-209. Atkins, I. M., and R. G. Dahms. 1945. Reaction of small grain varieties to greenbug attack. USDA Tech. Bul. No. ' 901, 30 pp. 10. 1 1-.~ ~- 12. 13. 14. 15. 16. 18 Bilsing, S. W. 1916. The greenbug or spring grain aphis. Texas Agric. Expt. Sta. Circ. 13. 8 pp. Bioletti, F. T., F. C. H. Flossfeder, and A. E. Way. 1921. Phylloxera resistant stocks. Calif. Agric. Expt. Sta. Bul. 331, 139 pp. Chada, Harvey L. 1959. Insectary technique for testing the resistance of small grains to the greenbug. Jour. Econ. Ent. 52: 276-279. Chatters, R. M., and A. M. Schlehuber. 1951. Mechanics of feeding of the greenbug (Toxoptera graminum (Rond.)) on Hordeum, Avena, and Triticum. Okla. Agric. Expt. Sta. Tech. Bul. No. T-40, 18 pp. Curtis, B. C., A. M. Schlehuber, and E. A. Wood, Jr. 1960. Genetics of greenbug (Toxoptera graminum (Rond.) ) resist- ance in two strains of common wheat. Agron. Jour. 52: 599-602. Dahms, R. G., and F. A. Fenton. and selecting for insect resistance. 131-134. 1939. Plant breeding Jour. Econ. Ent. 32: Dahms, R. G. to greenbugs from Oklahoma and Mississippi. Ent. 41: 825-826. 1948. Comparative tolerance of small grains Jour. Econ. Dahms, R. G. 1951. Preventing greenbug outbreaks. USDA Leaflet No. 309, 8 pp. Dahms, R. G., T. H. Johnston, A. M. Schlehuber, and E. A. Wood, Jr. 1955. Reaction of small grain varieties and hybrids to greenbug attack. Okla. Agric. Expt. Sta. Tech. Bul. T-55, 61 pp. Daniels, N. E., H. L. Chada, D. Ashdown, and E. A. Cleveland. 1956. IGreenbugs and some other pests of small grains. Texas Agric. Expt. Sta. Buli 845, 13 pp. Daniels, N. E., and K. B. Porter. 1958. Greenbug resistance studies in winter wheat. Jour. Econ. Ent. 51: 702-704. Fenton, F. A., and E. H. Fisher. 1940. The 1939 greenbug outbreak in Oklahoma. Jour. Econ. Ent. 33: 628-639. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 29. 30. 31. 32. 33. 34. Gardenhire, James H., and Harvey L. Chada. 1961. A inheritance of greenbug resistance in barley. In Press. I Science. Hunter, S. J. 1909. The greenbug and its enemies. Kat Univ. Bul. 9: 1-163. "~_ Hyslop, J. A. 1922. Summary of insezctfrconditions throu out the United States during 1921. USDA Bu}. 1103, 51 pp. J Le Pelley, R. 1927. Studies on the resistance of appleli the woolly aphis (Eriosoma lanigerum Hausm.). f, Pomol. and Hort. Sci. 6: 209-241. ’ MacLeod, G. F. 1933. Some examples of varietal resis - U; of plants to insect attack. Jour. Econ. Ent. 26: 62-67. Maxwell, F. G., and R. H. Painter. 1959. Factors affec A‘ rate of honeydew deposition by Therioaphis macu ' (Buck.) and Toxoptera graminum (Rond.). Jour. Econ. ' 52: 368-373. Painter R. H. 1941. The economic value and biol‘: significance of insect resistance to insect attack. Jour. y Ent. 34: 358-367. ' Painter, R. H. 1943. Insect resistance of plants in relai to insect physiology and habits. Jour. Amer. Soc. A 35: 725-732. ‘Y Painter, R. H. 1951. Insect resistance in crop pl The Macmillan Co., New York. 520 pp. Painter, R. H. 1958. Resistance of plants to insects. Rev. of Ent. 3:267-290. Silveira, A. Guido, and E. J. Conde. 1946. E1 pulgon I de los cereales del Uruguay. Univ. de la Republica, r video (Uruguay) Revista de la Facultad de Agron 41; 35-86. F Snelling, R. O. 1941. The place and methods of br " for insect resistance in cultivated plants. Jour. Econ. , 34: 335-340. Snelling, R. O. 1941a. Resistance of plants to insect at Bot. Rev. 7: 543-586. i- Wadley, F. M. 1931. Ecology of Toxoptem gramil especially as to factors affecting importance in the No 1* United States. Ann. Ent. Soc. Amer. 24: 325-395. 1944. Greenbug injury on barley va . Proc. Oklahoma ‘ W'a1ton, R. R. at Woodward, Oklahoma in 1943. Sci. 24: 38-42. Webster, F. M., and W. J. Phillips. 1912. The spring ;~l aphis or “greenbug.” U. S. Bur. Ent. Bul. No. 110, 153? Whitehead, F. E., and F. A. Fenton. 1940. An aeroi survey of greenbug injury in Oklahoma. Jour. Econ. __ 33: 762-768. - 51 Wood, E. A., Jr. longevity of two greenbug cultures. Div. Special Report W-l29. 1960. Comparative size, fecundity, USDA, ARS, Ent. , [Blank Page in Original Bulletin] i mm mm»: I nu meanness - nu nun Lnounounzs 4 coorunm sunon Location of field research units oi the Texas Agricultural Experiment Station and cooperating agencies QRGANIZATION CSPERATION Research results are carried to Texas farmers, ranchmen and homemakers by county agents and specialists of the Texas Agricultural Ex- tension Service joclay ,6 WeAearc/t .96 jomorrowii rogreczi au'_-..~ State-wide Research The Texas Agricultural Experiment Station is the public agricultural research agency I oi the State of Texas. and is one of the parts of the AcSM College of Texas. IN THE MAIN STATION, with headquarters at College Station, are 13 subj matter departments, 3 service departments, 3 regulatory services and h," administrative staff. Located out in the major agricultural areas of Texas 2O substations and 10 field laboratories. In addition, there are 13 coopera“ stations owned by other agencies. Cooperating agencies include the T . Forest Service, Game and Fish Commission of Texas, Texas Prison Sys U. S. Department of Agriculture, University of Texas, Texas Technolo if. College, Texas College of Arts and Industries and the King Ranch. Sol ~ experiments are conducted on farms and ranches and in rural homes. I THE TEXAS STATION is conducting about 450 active research projects, grouk in 25 programs, which include all phases of agriculture in Texas. u W’ these are: Conservation and improvement of soil Conservation and use of water Grasses and legumes Grain crops Cotton and other fiber crops Vegetable crops Citrus and other subtropical fruits Fruits and nuts Oil seed crops Ornamental plants Brush and weeds Insects Beef cattle Dairy cattle Sheep and goats “~- Swine I Chickens and turkeys , Animal diseases and parasites s‘ Fish and game Farm and ranch engineering “i Farm and ranch business Marketing agricultural produp, Rural home economics " Rural agricultural economics Plant diseases f . A Two additional programs are maintenance and upkeep, and central servli AGRICULTURAL RESEARCH seeks the WHATS, the WHYS. the WHENS, the WHERES and the HOWS oi hundreds of problems which confront operators ot iarms and ranches. and the many industries depending on or serving agriculture. Workers of the Main Station and the iield units of the Texas Agricultural Experi- ment Station seek diligently to find solutions to these problems. 0890