3-1053 AUGUST I966 INEL UEN CE ON GRAIN YIELDS AND YIELD COMPONENTS OF LEAF R US T OF WHEA T AND CROWlV RUST OE OATS a: measured by ISOGENIC RESISTANT AND SUSCEPTIBLE LINES V 2 TEXAS A8~»-b~ \Q\'J\OG\ Losses caused by leaf rusts, as expresse grain yields and percentages, and influences, yield components were determined for oats in 4 and for wheat from 1962 to 1965. This was f rated through the growing of isogenic resistant ‘ susceptible lines in yield trials at several loca in Texas. l Where rust infection occurred early or ‘vi severe during the fruiting period, oat yields reduced from 8 to 56 percent, and test weigh? the susceptible line were reduced. Wheat y were reduced from 3 to 29 percent. The n u! of seed per spike and seed size, as reflect weight per 500 seed, were reduced on the su tible line in many instances, but test weight w duced significantly only where rust infection high. I AF RUST 0F WHEAT i CROWN RUST OF OATS l- 1 ASURED B Y ENIC RESISTANT SUSCEPTIBLE LINES" I. M. Atkins Maximino Alcala de Stephano O. G. Merkle R. A. Kilpatrick* AAUENCE ON GRAIN YZELDS AND YIELD COZIIPONENTS Leaf rust of wheat, Puccinia recondim Rob. ex Desm., and crown rust of oats, Puccinia cornanata Cda. var. Avenae Fraser and Led. Eriks, are the most destructive diseases of wheat and oats, respectively, in Texas. Owing to the relatively mild winter temperatures in. all except the High Plains area of Northwest Texas, the leaf rusts may become established in early fall and persist throughout the winter. Leaf rust frequently overwinters and spreads slowly dur- ing the winter as far north as an east-west line from Abilene to Dallas. Crown rust is more sensitive to low tempera- tures and usually does not overwinter north of the Temple- Waco area of Central Texas. Serious losses in grain production from rusts are reCordfid for 1935, 1949, 1957 and 1958. Less extensive losses have occurred in many other seasons, yet the dis- eases are always a potential threat to the crop. The greatest recorded loss was that of 1949 when it was estimated by Atkins (2) that leaf rust of wheat caused a loss of 12.4 million bushels and crown rust of oats caused a loss of 3 million bushels. Edson et al. (6) estimated that 237,000 bushels of wheat and 954,000 bushels of oats were lost to leaf rusts in 1935. Futrell and Atkins (8) estimated the grain loss of wheat in 1957 at 1.5 million bushels and in 1958 at 2.2 million bushels. Oat losses from crown rust were estimated at 5.8 million bushels in 1957 and 2.6 million bushels in 1958. The influence of these rusts on forage production, drouth and low temperature survival is poorly documented. It is known that small grain pastures may be destroyed from , 30 to 45 days earlier than normal in many seasons by rust epidemics. During the 1962 season, when an estimated 24 percent of the wheat crop in the High Plains area of Texas was winterkilled, it is believed that the heavy infec- tion of leaf rust on this crop greatly influenced survival of wheat. Texas annually seeds more than 6 million acres of small grain of which more than 1 million acres are *Respectively, agronomist and Small Grains Section leader, Texas Agricultural Experiment Station and Crops Research Division, ARS, USDA; former Texas A&M graduate student, now agrono- mist, Ministry of Agriculture, Mexico City; and agronomist and pathologist, ARS, USDA, College Station. 3 seeded exclusively for livestock pasture. Damage by the rusts is an important consideration in forage use. The measurement of losses from rust under field con- ditions is difficult and subject to many errors. Loss esti- mates in an area or state are especially difficult because of variation in environment and degree of susceptibility of the varieties grown. Most loss estimates for states or areas are based simply on judgement of one or more workers in the area. Comparing fungicide-sprayed plots with un- sprayed control plots is one method of measuring the loss. However, this may be difficult to carry out if extended wet periods prevent adequate protection with fungicides and, furthermore, may introduce a third factor which cannot be evaluated, that of control of other diseases. The use of near-isogenic or closely related lines differing only in susceptibility to the particular pathogen offers one means of measuring the influence of the disease on the plant and the damage in terms of reduced grain o-r forage yields. Literature Review The effects of leaf rust and crown rust have been the subject of extensive research. Mains (15) showed that grain yield of wheat could be reduced by 37 percent when 100 percent leaf rust infection developed by the time of flowering. When infection occurred before flowering, the yield was reduced largely by a decrease in the number of kernels per spike, but when infection occurred after flower- ing, the yield was lowered by a reduction in kernel weight. ]ohnson and Miller (12) demonstrated with greenhouse plants that yield losses were due to a reduction innumber of spikes and in size of kernels. They showed that heavy infection resulted in rapid deterioration of the roots as indicated by root discoloration, a decrease in fibrous roots ' and a marked loss by root rotting. Peturson et al. (19) found that heavy infections of leaf rust initiated at an early stage of plant development reduced the size and num- ber of kernels in susceptible varieties of wheat. Newton (18) controlled leaf rust on wheat with sulphur dust and found that 4O percent infection of the leaves caused a 1O percent reduction in grain yield. Murphy et al. (16, 17) demonstrated the important reduction in yield and test weight caused by crown rust infection and proved that rust infection could make plants more susceptible to freeze injury. Recently, Fleischmann and McKenzie (7) reported that 5O percent natural infec- tion of oats at flowering caused a 25 percent reduction in grain yield but, when infection came later than flowering, only 1O percent yield loss resulted. Isogenic lines as a means of measuring the influence of simple characters on yield or growth of plants was first suggested by Atkins and Mangelsdorf (5) in 1942. The method was demonstrated by comparing grain yields of 1O pairs of awned and awnless isogenic lines of wheat by Nor- 4 ris and Atkins (4). During recent years the me A been used to measure the effects of awns, awn head-type, growth habit, seed color and other morp characters on yield, yield components or quality r, Craigmiles (5) was the first to measure losses u rust utilizing isogenic lines, although Suneson (21 \_ compared yields of back-crossed rust and smut resis of wheat with the susceptible parent variety. Gr’ (9) developed Marquis monogenic wheat lines,‘ possess one, two or more genes for resistance to st Johnson and Heyne (15) developed Wichita wh each with a major gene for leaf rust resistance. j material has been developed for crown rust by Marr f USDA pathologist at Ames, Iowal, an-d B. I_ USDA pathologist at St. Paul, Minnesota2 has d monogenic oat stem rust lines. Such material off, sibilities for the study of the pathological and physi characteristics and potentials of the host and - where the effect of one or more genes in a co t diverse background can be determined. The vi isogenic lines in physiologic studies was pointed t‘ demonstrated by Rowell et al. (20). ’ Lyles et al. (14) found that 2 stern rust resis 5 genic lines were higher in reducing sugars than t ceptible counterparts. Antonelli and Daly (1) f0 f isogenic lines resistant to race 56 of stem rust essentially the same increase in decarboxylation susceptible lines during the first 2-3 days of inf - " subsequently developed values eight times as greastj susceptible lines. Hilu (11) used isogenic rust i and susceptible corn lines to study host-pathogen ships from initial stages of infection to fruiting A pathogen. Weber (22) developed isogenic line pairs 0f‘- pena, Hawkeye, Ford and Clark soybeans with (No) ; lating and (no) nonnodulating characteristics for ~i strating, studying and evaluating the nodulation- ' relationships. Another pair was developed to stu iron utilization efficiency (Fe) and inefficiency ( soybeans. * Although many interesting and valuable studi be carried out with isogenic lines, a note of cau their use was made by Harding and Allard (10).. showed that mutations or segregation of charact observed -during development of the isogenic lin; cause errors or inadequate comparisons. Memeriezli‘ and Met/weir Isogenic or closely related lines differing only ” major characteristic may be developed by: Back _ ‘Private correspondence with Marr Simons, USDA path Iowa State University, Ames, Iowa. A zPrivate correspondence with B. j. Roberts, USDA path University of Minnesota, St. Paul, Minnesota. . , ly to each parental type; selecting a recognizable zygote through several generations until all other able characters become uniform; or selecting in ad- - generations in a line which appears morphologically but is segregating for the character one wishes to . Each method has advantages and disadvantages. oat isogenic or closely related lines used in this were selected from a morphologically uniform prog- _ _ ow, which was segregating for crown rust reaction, lie sixth generation of the cross Fulwin 2x Lee x Vic- 3x Red Rustproof 4x Victoria x Richard 5x Bond x u 2x Hajira-joanette 5x Landhafer. Seed from iidual panicles were increased in F7 progeny rows. most uniform pairs were increased in F8 to- supply seed e ninth generation for the 1959 yield trials. The r gene for resistance was that from Landhafer, and Lprevalent crown rust races in the nursery at that time 202, 203, 213 and 216. Races 290 and 294, to which afer and both isogenic lines are susceptible, became ialent in southern Texas in 1960 so the test was dis- "nued. The 1959 tests were grown at Beeville, Prairie i and College Station in an area where rust epidemics g common. The wheat isogenic lines were selected from a mor- ‘logically uniform progeny row, which was segregating leaf rust reaction in the seventh generation of the cross ivvalocho x Wichita 2x Hope - Cheyenne 3x Wichita, C.I. 703 4x Kenya Farmer. Seed of individual spikes were a eased in progeny rows, and further selected for uni- Figure l. Showing uniformity of morphological characters of w; lines of wheat 6001965, susceptible, and 60C4968, istant. Figure 2. Leaves of isogenic lines of wheat — Selection 6001968 (left of center), resistant, and Selection 6001965 (right of center), susceptible. fo-rmity in F8 and F9 in 1961 and 1962. During 1962, three pairs of isogenic lines were grown at College Sta- tion and Denton, and from these the strains 60C4968 (re- sistant) and 60C4965 (susceptible) were selected as the most uniform and were used in the 1963, 1964 and 1965 tests. The uniform plant type of these strains is shown in Figure 1 while the rust reaction is shown in Figure 2. Milling and baking tests show these strains to have similar quality characteristics. Races of leaf rust of wheat prevalent in Texas during the testing period of 1963-65 were predominantly UN 2, 5, 9 and 13. Under some conditions, light infection devel- oped on the resistant line late in the growing season but, in most tests, the infection was typical of that shown in Figure 2. Leaf rust notes were taken on several dates dur- ing the season to record date of initial infection and rate of spread. Yield trials of the isogenic lines were conducted as part of the Texas Intra-State Small Grain Performance Trials to determine the prevalence, severity and influence of the leaf rusts and as a basis for estimating lo-sses in Texas. Plantings were made in randomized blocks of four replications, with the request to each cooperator that the pairs be located side by side in each replication. Plots were 4-row, 10-foot nursery plots with 12-inch spacings between rows. Eight feet of the two center rows were harvested for yield and other determinations. TABLE l. GRAIN YIELDS, TEST WEIGHT AND CROWN RUST REACTION OF RESISTANT AND SUSCEPTIB GENIC LINES OF OATS AT THREE TEXAS LOCATIONS IN 1959 College Station Prairie View Beeville Grain Test Grain Test Grain Test yield, weight, yield, weight, yield, weight, bushels pounds Percent bushels pounds Percent bushels pounds Strain Rust reaction per acre per bushel rust per acre per bushel rust per acre per bushel 5701446 Resistant line 45.4 a0 2 33.7 25 o “$18.8 2s 57Cl447 Susceptible line 43.8 30 55 22.8 22 100 8.8 23 Diffi-res. vs. susc. +l.6NS +109‘ +l0.0‘ 57Cl453 Resistant line 50.9 29 Tr 34.6 28 Tr 19.4 25 57Cl449 Susceptible 45.9 29 58 22.4 23 100 8.2 23 DifL-res. vs. susc. +5.0NS +122‘ +112‘ 57C1462 Resistant line 40.2 32 1 19.9 23 Tr 13.1 26 57Cl461 Susceptible line 35.7 29 69 13.6 20 100 5.1 23 DifL-res. vs. slsc. 4.5NS 6.3” +8.0‘ Average Resistant line 45.5 30.3 1 29.3 25.3 Tr 17.1 25.3 Susceptible lines 41.8 29.3 61 19.6 21.7 100 7.4 23.0 Diflzl-res. Vs. susc. +3.7NS 9.7‘ 9.7‘ Reduction in percent 8.4 33.0 56.8 ‘Significant at the 0.1 percent level ‘Significant at the .05 percent level Only grain yields were obtained in the oat trials. As turity and yields were reduced on an average of 3 ' part of a thesis problem by the second author, yield com- ponents were determined for the wheat trials in 1963 and for those locations where rust developed in 1964. Stands were determined from culrn counts of the entire harvested bundle, kernels per spike from 2O spikes per replication, weight per 500 seed from five samples per plot and test weight from four test samples of the composite grain of all replications. As differences in tillering, kernels per spike, weight per 500 seed and test weight were equal or nonsignificantly different in 1963 where rust was not present, it was considered unnecessary to make these deter- minations in other years, except where rust influenced yield. Experimental Results Oats: Data obtained in 1959 at Beeville, Prairie View and College Station -for three pairs of isogenic lines of oats are given in Table 1. The winter season at Beeville was favorable for normal growth until near fruiting time. Crown rust infection occurred during the winter and reached about 4O percent severity before heading time. Reserve moisture was exhaused by heading time, and very little precipitation was received .during the fruiting period. Yields were very low but the yields of the susceptible isogenic lines were significantly reduced, averaging 7.4 bushels compared to 17.1 bushels for the three resistant lines or a reduction of 56.8 percent in yield. Growing conditions were much more favorable at Prairie View and College Station. Crown rust appeared at Prairie View in the late tiller to boot stage of growth and reached 5O percent infection several days after first head. Near 100 percent infection occurred before ma- 6 cent. At College Station rust infection occurred {is heading but developed slowly so that a maximum of y’ 61 percent infection was reached at maturity. G A , conditions for the crop were favorable so yields reduced only 8 percent on the susceptible lines, an was not statistically significant. Figure 3 shows 3Q ically the influence of severe early infection on grain i, of oats. Wheat: Data on grain yields of isogenic lines? number of locations from 1962 to 1965 are given in i 2. Yield components data at a smaller number of l A», are given in Table 3. Stands, as indicated by num spike-bearing culms, were determined but differences i. nonsignificant in all but one instance. The 1962 at College Station showed a smaller number of cul the resistant lines for some unknown reason. i The experiments were carried out during a peri very dry springs so that rust development was in instances stopped by dry, windy weather. Rust inf‘ of importance also was generally late in developing so.’ less damage would be expected. Data for 1962 are averages of three pairs of t: lines at two locations and, though percentages were 1 the rust development was mostly after heading plants. Yields were reduced at both locations but was relatively small and was nonsignificant at Colle tion. Weight of seed was reduced significantly I susceptible line. Number of seed per pike was not si cantly reduced although it was lower on the susc ~ line at both locations. 10o l- ;- the three strains tested in 1962, the isogenic 4965 and 60C4968 were selected as the most R morphologically and were used in all tests in 1963, id 1965. The 1963 season was extremely dry dur- ' and May so that leaf rust, which had been present ' amounts on seedlings, spread very slowly. Figure 1 the development of rust in relation to the fruiting _i at Beeville, College Station and Temple in 1963. 91h rust was present at Beeville long before heading, _ed only 6O percent infection by maturity. Grain were very low. The resistant line produced 1.6 57 percent f ’ yield reduction / 33 percent I K yield reduction Fruiting period - Beeville / E, 75 _ __ ._ —. 1 -/_ _- -_ _/ H . E / I 9 / 7 Crown rust develop- 3 47/ / 5 a o r U .'\' _ tmg penod and yield 5 5o qs/ ' Fruiting period - Prairie View . u " W i. ._ __ _ i- _ ._... f by crown rust on sus- 3 f; / ; g4 enic lines of oats at 091/ ‘as 8,P°“‘e““ , - _ _ a y yield reduction muons 1n Texas, 1959. é, / g5“ ‘ 2s -$,§7’/ , s‘? ’ / 59/ / eon; ‘r {i fi / I I I I l I 1o 2o 3o 1o 2o 30 5 March April May bushels per acre more than the susceptible line, which was not statistically significant. Also, both number of seed per spike and weight of seed were greater for the resistant line, although again not significantly greater. The only significant reduction in yieldwas at College Station where the resistant line yielded 10.9 bushels or 29 percent more than the susceptible line and its test weight was 58.0 pounds compared to 56.5 for the susceptible line. As rust devel- oped early and reached 35 percent infection by heading, the number of seed per spike was significantly reduced and the weight of seed was reduced, but not significantly ' 2. GRAIN YIELDS AND LEAF RUST INFECTION OF RESISTANT AND SUSCEPTIBLE ISOGENIC LINES OF R WHEAT GROWN AT TEXAS LOCATIONS, 1962-65 ' Station 18.0 18.5 +0.1Ns 37.7 20.8 1 1 11.7 10.1 20.0 20.6 1c 26.2 25.4 .1 28.4 27.5 +0.9‘ 24.7 21.9 i othe 26.3 23.7 211 1 on i d, dryland . d, irrigated j 0rd, irrigated ,1; ' Station 3 83 33 98 e 10R 00 or 0 Tr 0Tr 45 ll 3,3 i. 67 0 Tl‘ gcothe ‘1 0 0 i gIZOII i and, dryland 1 and, irrigated 10rd, irrigated 1962 1963 1964 1965 Suscep- Resistant Resistant Resistant Resistant Resistant tible vs. vs. vs. vs. average, average, Suscep- Suscep- Suscep- Suscep- Suscep- Suscep- Suscep- three three tible, Resistant tible, tible, Resistant tible, tible, Resistant tible, tible, lines lines difference 60C4968 60(14965difference 60C4968 60C4965difference 6001968 60C4965 difference Grain yield, bushels per acre +10.91 37.1 33.4 +3.71 14.8 11.8 +3.01 + l.6NS 23.0 17.7 +5.31 9.2 0.3 +2.91 _ 0.018s 42.4 38.4 +4.0Ns 25.0 20.0 +5.01 + 0.8NS 27.3 27.2 +0.lNS 29.0 29.0 +0.6NS + 2.8NS 37.4 30.9 +0.51 20.0 24.1 +2.51 + 2.6NS 14.6 14.9 _0.3NS 15.5 15.3 +0.2NS 10.0 7.2 +2.8NS 8.4 8.3 +0.1NS 13.0 13.2 _0.2NS Destroyed by hail 43.0 39.5 +3.5NS Destroyed by hail 50.7 48.9 +l.8NS 31.6 32.4 _-0.8NS Leaf rust, percent at maturity Tr 70 l0 90 10R 20 . 10 30 Tr 15 10 100 0 Tr Tr 100 0Tr 40 20 40 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ‘cant at the 0.1 percent level. lficant at the .05 percent level. TABLE 3. YIELD COMPONENTS FOR RESISTANT AND SUSCEPTIBLE ISOGENIC LINES OF WINTER GROWN i, AT TEXAS LOCATIONS 1962 1963 1964 1965 Suscep- Resistant Resistant Resistant Resistant tible vs. vs. vs. . average, average, Suscep- Suscep- Suscep- Suscep- Suscep- Suscep- three three tible, Resistant tible, tible, Resistant tible, tible, Resistant tible, , lines lines difference 60C4968 60(14965 difference 60C4968 60C4965 difference 60C4968 60C4965 Weight per 500 kernels, grams i l’ College Station 17.7 16.1 +1.61 16.4 15.4 +l.0NS 16.9 16.1 +0.8’ 16.0 15.7 Beeville ' 13.0 12.0 +1.01 12.5 10.7 McGregor 16.2 16.9 _0.71 17.9 15.3 +2.3‘ 14.6 12.0 Temple 18.7 17.0 +1.71 15.8 14.8 Denton 17.2 16.1 +1.12 15.2 16.4 _1.21 16.7 15.8 +0.88‘ Chillicothe 16.1 16.4 +0.3NS Wellington Bushland, dryland Bushland, irrigated Stratford, irrigated Number of seed per spike College Station 24.3 22.7 +1.6NS 22.3 18.4 +3.9‘ 21.0 20.8 +0.2NS Beeville 17.0 15.6 +1.4NS McGregor 14.2 15.7 -_ 1.5NS 26.7 23.9 +2.8” Temple 16.6 17.2 _1.4NS Denton 29.7 28.7 +l.0NS 24.9 23.9 +1.02 Chillicothe 20.8 18.7 +2.1NS Bushland, dryland Bushland, irrigated Stratford, irrigated ‘Significant at the .01 percent level. zSignificant at the .05 percent level. so. Leaf rust infection occurred at Temple about midway of the fruiting period and reached only 45 percent infec- tion at maturity so the effects on yield and yield com- ponents were small. Leaf rust did not occur at other stations so damage over the state was only a trace. The 1964 spring season was again very dry during fruiting of wheat, and rust developed rather late, except at Beeville and College Station. Yields were significantly 100 '- reduced on the susceptible line at College Station, -"i and Denton as were number of seed per spike and, of 500 seed. Although the yield of the susceptib was reduced at McGregor, variability was high so t‘ At all 5a the main wheat-growing area of Texas, rust was: factor in yield, and differences in grain yields betw lines were nonsignificant. The 1965 season was exc ference was not statistically significant. / z 29 percent yield reduction Fruiting period - Beeville I |- _ _ _ _ _ _ _ _ _ .._ -74 a 75 I g / 1- “S '3 Percent 131st ' 362113,, _- - - " .. i.’ _ .- - "- " I 14 percent _ '- § l/ Yield reduflim‘ Figure 4. Leaf rust 1T t‘ . . . . .2 50 - I ment, fruiting PCHOd . / / Fruiting period - College Station W ICdIICfiOIIS Oll SIISCC tl i‘ Q’ . l/ ‘i ' _ _' ' " a? 3 percent genic lines of wheat at‘. / ' 1d d ct’ n . . .- / y“ re u 1° locations in Texas, 1963. - C’ ’ / we’; e$ 2S I- , 00¢, w / a " Fruiting period - Temple Q / ‘o’ a m! 0 / 01°F’, I Y. / 1 /1 1 1 1 1 1 1 1O 20 3O l0 2O 3O 1O March April May 1i p; May in Central Texas. Leaf rust infection as the fall and survived to spread slowly during J e wintegwas very mild, so the cold requirement jlines was not fulfilled and they did not head - Beeville. Yields at that station were very 10W. i“ and weight per 500 seed of the susceptible line ificantly reduced at College Station, Beeville, and Denton. Number of seeds per spike was ‘v in 1965. Leaf rust did not develop to any importance in the Rolling or High Plains, so H between lines for these stations are non- Discussion ‘use of isogenic lines, differing in disease reaction, to provide a practical and efficient method of '1 losses caused by a disease. Where there are Qnges in races or biotypes of the disease, from season, as occurs in the cereal rusts, this presents I of providing germ plasm adequate to protect and measure the losses. In the present study, the isogenic lines of oats, differing by the Landhafer gvided a good measure of rust damage in 1959, _pid increase of race 290 and 294 made it imprac- - these lines in 1960. isogenic lines of wheat were adequate for measur- during the period of study because leaf rust ly equal in yielding ability when rust was not a QWhen yields were reduced by rust, this was usually 'ed by a reduction in number of seed per spike eight per 500 seed on the susceptible line. This i; eement with studies by Mains (15), johnson and (12) and Murphy (17) who have studied the of the pathogens and the host under controlled I» s. The great influence which time of rust infec- jermines was demonstrated in Figures 3 and 4 and pl the results of Mains (15), Fleishmann (7) and » Test weights of the wheat lines were not signfi- different in most instances, even when rust was ring the 1965 season, when it became apparent f rust would do considerable damage to wheat in ,- Texas, estimates were made before harvest by y workers at the stations in the area. These esti- (were averaged by R. A. Kilpatrick?’ to give a com- opinion of the loss, This was calculated to be 10 t for the Central-{Texas area which grows about 8 of the Texas crop. Extended to the state acreage, resented an estimated 3.5 percent of the Texas i‘ The losses, as measured by the isogenic lines, were i-t report of research by R. A. Kilpatrick, USDA pathologist, _ A&M University, College Station. '3 fairly stable. The isogenic lines proved to be ‘ 2O percent for College Station, 31.5 percent for Beeville, 22 percent for McGregor, 3 percent for Temple and 10 percent for Denton. It should be pointed out that is0geni.cs should be replicated and arranged in pairs so that soil variability in the test will not complicate the measurement of losses. Furthermore, if used on experimental field stations where rust is inoculated into nearby breeding ma- terial, the amount of infection and loss may be exaggerated as compared to the commercial crop in the area. Acknowledgement Appreciation is herewith expressed for cooperation in growing the isogenic lines at field stations at Beeville, McGregor, Temple, Denton, Chillicothe, Bushland, Strat- ford and Wellington, respectively, by the following agron- omists: Lucas Reyes, M. Norris, U. D Havelka, H. Gardenshire, K. A. Lahr and K. B. Porter. The contents of this publication are a result of cooper- ative research by the Department of Soil and Crop Sciences, Texas A8zM University, andthe Crops Research Division, ARS, USDA. Literature Cited I. Antonelli, E. and Daly, j. M. Decarboxylation of indoleacetic acid by near-isogenic lines of wheat resistant or susceptible to Purrinia graminis f. sp. lritici. Phytopathology 56:610- 618, june 1966. 2. Atkins, I. M. 1950. Diseases of small grains in Texas in 1949. Plant Dis. Rptr. 34:40-42. 3. Atkins, I. M. and Mangelsdorf, P. C. 1942. The isolation of isogenic .lines as a means of measuring the effects of awns and other characters in small grains. Agron. j. 54:667-668. 4. Atkins, I. M. and Norris, M. j. 1955. The influence of awns on yield and certain morphological characters of wheat. Agron. j. 47:218-220. 5. Craigmiles, j. P. 1956. Oat disease studies. Georgia Agr. Exp. Sta. Tech. Bul. N.S. 7. 6. Edson, H. A., Wood, j. I. and Nance, N. W. 1935. Esti- mate of crop losses from plant diseases in the United States in 1935. Plant Dis. Rptr. Suppl. 94:46-51. 7. Fleisohmann, G. F. and McKenzie, R.I.H. 1965. Yield losses in Garry oats infected with crown rust. Phytopathol- ogy 55:767-769. 8. Futrell, M. C., Atkins, I. M., and Hobbs, C. D. 1959. Un- usual occurrence of small grain diseases in Texas in 1957 and 1958. Plant Dis. Rptr. 43777-781. 9. Green, G. j., Knott, D. R., Watson, I. A., and Pugsley, A. T. 1960. Seedling reactions to stem rust of lines of Marquis wheat with substituted genes for rust resistance. Canad. j. Pl. Sci. 40:524-538. 10. Harding, j., and Allard, R. W. 1965. Genetic variability in highly inbred isogenic lines of the lima bean. Crop Sci. 52203-206. 11. Hilu, H. M. 1965. Host-pathogen relationship 0f Puccinia sorgbi in nearly isogenic resistant and susceptible seedling corn. Phytopat.hology 55:563-569. 12. 13. 14. 15. 16. 17. 10 johnson, c. 0., and Miller, E. c. 1951. infection on certain varieties of wheat. 23:1-12. Effect of leaf rust j. Am. Soc. Agron. johnson, C. O. and Heyne, E. G. 1964. Wichita wheat backcross lines for differential hosts inidentifying physiologic races of Puccini}: recondim. Phytopathology 54:385-388. Lyles, W. E., Futrell, M. C., and Atkins, I. M. 1959. Rela- tion between reaction to race 15B of stem rust and reducing sugars and sucrose in wheat. Phytopathology 49:254-256. Mains, E. B. 1959. Effect of leaf rust (Puccinia triticiana) Eriks. on yield of wheat. Phytopathology 49:254-256. Murphy, H. C. 1939. Effect of crown rust and stem rusts on the relative cold resistance of varieties and selections of of oats. Phytopathology 29:763-782. Murphy, H. C., Burnett, L. C., Kingsolver, C. H., Stanton, T. R., and Coffman, F. A. 1940. Relation of crown rust 18. 19. 20. 21. 22. infection to yield, test weight and lodging of ca; pathology 30:808-819. ~ Newton, Margaret. 1938. The cereal rusts Empire j. Exp. Agri. 6125-140. ‘i Peturson, B., Newton, Margaret, and Whiteside, A. The effect of leaf rust on the yield and quality Canad. j. Agr. Res. 23 Ser. C-D:1_05-114. Rowell, j. B., Loegering, and Powers, Genetic model for physiologic studies of meohani; ing development of infection type in wheat stem ru pathology 532932-937, August 1963. Suneson, C. A., Riddle, O. C., and Briggs, F. _, Yields of varieties of wheat derived by backcrossin j. 35:355-840. ‘i Weber, C. R. 1966. Nodulating and nonnodulatinv isolines. Agron. j. 58:43-48. 5 .' [Blank Page in Original Bulletin] Texas AS-M University Texas Agricultural Experiment Station College Station. Texas 77841 Xififl» Director Publication-Annual Report or Bulletin or Report of Progress Permit 1105 OFFICIAL BUSINESS n‘ ‘f’ Penalty for -~ f payment ’ I