GrainGenes

Louisiana State University Agricultural Center

Department of Agronomy, 104 Madison B, Sturgis Hall, Baton Rouge, LA 70803-2110 USA. S.A. Harrison, C.A. Clark, P.D. Colyer, C.A. Hollier, J.S. Russin, R.W. Schneider, B.L. Tillman, and J.D. Thompson.

Wheat breeding and variety testing. The wheat breeding program completed its tenth year in 1994. Emphasis continues to be on development of high-yielding lines with good test weight and resistance to leaf rust, Septoria leaf and glume blotch, and bacterial streak. The oat breeding program is concentrating on lodging (culm rot), crown rust, stem rust, and barley yellow dwarf resistance. Short and hull-less types also are targeted. About 300 new wheat crosses were added in 1994. The switch from pedigree selection to mass selection for the F₂ and F₃ generations led to planting of about 24,000 F₄ head rows in November, 1994. The F₂ and F₃ populations for 1994-95 include 1,200 75 square-foot plots (about 3/each of 400 crosses). Half of these were planted in mid-October (3 weeks earlier than normal) to evaluate potential to select lines that do not head out early when planted early. Some spring x winter populations set seed in December and January. These should be frozen out in February. Harvested heads will be planted later than normal in 1995 to select for low-vernalization lines. This should result in a high proportion of photoperiodic lines that can be planted over a broader range of dates. Eight wheat lines have been advanced to statewide performance trials for 1995 and an additional 387 lines will be evaluated in preliminary yield trials. About 50,000 total head rows were planted in the fall. The oat breeding project includes 20 lines in statewide yield trials and about 8,000 head rows. Breeder seed increases of superior lines was initiated for 1995. (Harrison, Thompson, and Tillman)

Wheat diseases and fungicide evaluation in North Louisiana. For the second consecutive year, disease severity on winter wheat in northern Louisiana was very low. The incidences of bacterial blight (Xanthomonas campestris pv. translucens) and leaf rust (Puccinia recondita f. sp. tritici) were very low, while the severities of Septoria leaf and glume blotch (Septoria spp.) were moderate. Leaf rust developed on susceptible varieties very late in the growing season and probably had little effect on yield. A field trial of labelled and experimental fungicides for the control of foliar diseases of wheat (cv. Florida 302) was conducted at the Red River Research Station in Bossier City. The severity of leaf rust was low, with the untreated control averaging only 13 % rust on the flag leaf at Feekes' stage 10.8. Eight of 10 fungicide treatments reduced leaf rust compared with the untreated control. The severity of leaf rust in plots treated with Kocide 101 and the experimental fungicide, SAN 619 at 1.27 oz product/acre, was not significantly different from that in the untreated control. There were significant differences in the severity of leaf blotch occurred among fungicide treatments. Grain yields, which averaged 53.3 bu/acre, were not significantly different among treatments. (Colyer)

Wheat production in 1994. Wheat was harvested from 66,592 acres by 589 producers, a drop from the 98,804 acres harvested by 711 producers in 1993. Yields for 1994 averaged 37.03 bushels per acre, an increase from 26.08 bushels per acre, resulting in a total production of 2,465,838 bushels, down from the 2,576,467 bushel crop of 1993. The gross farm value of the 1994 crop was estimated at $8,013,976. The reduction in acreage was caused by adversities in planting conditions and late-season freezes from the season before. The increase in yield per acre was due to good growing conditions and lower than normal disease pressure. Yield losses from leaf rust were about 2 %, whereas losses from the stem and stripe rusts were <1 %. Other leaf and glume diseases caused negligible losses. Total yield loss from a combination of all diseases was <5 %. (Hollier)

Fungicide evaluations. Field tests of labelled and experimental fungicides were conducted on rust-susceptible Coker 9877 at Baton Rouge, Alexandria, and Bossier City. Leaf disease pressure was low at all locations. Of the labelled compounds, Tilt, Bayleton, and Bayleton + Manzate 200 provided limited control of leaf rust and Septoria leaf blotch. Fusarium head scab was present at low levels in plots but was not controlled by these fungicides. Only one experimental compound, RH7592 (Rohm & Haas), was tested this year. As in previous years, foliar disease control with this material rivalled or exceeded that provided by the standard recommended compounds. (Russin)

Bacterial suspensions on seed. Wheat (FFR 525) seed were treated with each of eight bacteria suspensions that previously were effective in reducing seedling disease in water-seeded rice. Emergence in the field was recorded at 15 and 30 days after planting and compared to nontreated and fungicide treated controls. Relative to the fungicide control, three bacterial isolates accelerated emergence at 15 days after planting, and seven of eight isolates resulted in higher emergence at 30 days after planting. (Schneider)

Bacterial streak research on soft red winter wheat. Field studies conducted over several year-locations showed that ratings of black chaff and bacterial streak symptoms caused by X. campestris pv. translucens were not correlated. Greenhouse studies confirmed this. Greenhouse results showed that Florida 304 is susceptible to bacterial streak, but resistant to black chaff and that Coker 9877 is susceptible to black chaff, but is intermediate in reaction to bacterial streak. The cultivar Terral 101 is resistant to both symptoms, whereas the F₆ breeding line LA85426 is susceptible to both symptoms. Our research indicates that certain genotypes can be resistant to black chaff but susceptible to bacterial streak and vice versa. Yield loss has been associated with bacterial streak but not black chaff. Therefore, it appears that breeders should focus on breeding for resistant to bacterial streak. The inheritance of resistance to bacterial streak in winter wheat breeding populations at the Louisiana Agricultural Experiment Station is quantitative. In three F₂-derived populations, heritability (parent-offspring regression) of resistance averaged 0.34. Residual variance was 2 to 4 times as large as genotype by environment interaction variance. Average entry mean heritabilities increased from 0.31 to 0.46 using 3 replications and 1 environment and from 0.31 to 0.55 using 1 replication and 3 environments. Out of 380 wheat lines screened over 2 years, 57 have shown resistance in Louisiana. The only soft red winter wheat cultivar among the group was Terral 101, which is the most resistant cultivar yet identified in Louisiana. GA 22 triticale also was very resistant in our tests. The group of 57 will undergo a final field screening in 1995. (Tillman, Harrison, Clark, and Russin)

Personnel. Barry Tillman completed his Ph.D. in the wheat breeding program in December, 1994. He is currently publishing results of his research on bacterial streak of wheat. Dr. Tubajika Kyembi joined the wheat pathology program as a postdoctoral associate. He will follow up on the research on bacterial streak of wheat and work on other diseases of wheat.

Publications. Shah SA, Harrison SA, Boquet DJ, Colyer PD, and Moore SH. 1994. Management effects on yield and yield components of late-planted wheat. Crop Sci 34:1298-1303. Harrison SA et al. 1994. Performance of small grain varieties in Louisiana, 1993-94. LAES Mimeo Series No. 90. 92 p. Russin JS, Tillman BL, and Harrison SA. 1994. Supplemental spring nitrogen reduces severity of black chaff in Louisiana. Biol and Cul Tests. Tillman BA. 1994. Breeding wheat for resistance to bacterial leaf streak caused by Xanthomonas campestris pv. translucens. Ph.D. dissertation, Louisiana State University.