GEORGIA / FLORIDA
UNIVERSITY OF GEORGIA
Department of Agronomy, Griffin, GA 30212, USA.
J.W. Johnson, R.D. Barnett, B.M. Cunfer, and G.D. Buntin.
The 2001 Georgia winter wheat crop was grown on about 300,000
harvested acres. The crop production resulted in a state average
yield of 53 bu/acre. Overall, the season was characterized by
a mild and dry winter followed by a dry and hot spring. Cool and
dry conditions prevailed through the grain-filling stage and helped
reduce the infection from powdery mildew and leaf rust. Due to
excessive rainfall at harvest, several thousands of acres were
abandoned in the field and grain was severely sprouted.
92485E15 was released as an exclusively cultivar. Selected from the cross 'GA831276/GA861278 (Saluda/FL74265)/(Gore/FL302)', 92485E15 is a medium-maturing, white-chaffed, medium-height line with good straw strength. The cultivar matures an average of 1 day earlier than AGS 2000 in Georgia. 92485E15 is moderately resistant to the currently predominant races of powdery mildew, leaf rust, and biotypes of Hessian fly in Georgia.
Four SRWW germ plasm lines resistant to St. nodorum and other foliar pathogens were released. These lines also have good resistance to leaf rust, powdery mildew, and Hessian fly.
GA 84202 (Novisad138 /2/VPM/Moisson//FL74265),
GA85240 (Hunter/FL742765//IN71761/Coker 80-13),
GA85410 (Hunter/2*GA74-33 (Holley/McNair 701), and
GA861460 (Coker 9323/GA 100).
A wheat-rye translocation line (T2BS·2RL) has been developed for resistance to biotype L of Hessian fly. AFLP analysis using 64 primer pairs identified 2RL-specific polymorphisms between an NIL with 2RL and Hamlet. Nine primer combinations identified 12 reproducible polymorphic fragments in the NIL with 2RL. These 12 fragments were cloned and sequenced to converting AFLP markers into STSs. A comparison of the 12 sequences with nonredundant accessions in the NCBI database using the BLAST search option indicated that one fragment of approximately 200 bp (amplified using primer combination E+AAC / M+CTA) was highly homologous with the rye-specific, repetitive sequence 8173-1 and Wis-2-1A, a retrotransposon-like element in wheat. Two STS primers (SJ07 and SJ09) out of 12 STS primer sets enabled the detection of polymorphisms between NIL with 2RL. Our data suggest that primer set SJ07 amplifies a 2RL-specific fragment of diagnostic value.
Foliar diseases caused little damage to wheat during 2001 because of a dry spring. Powdery mildew, leaf rust, and Stagonospora leaf and glume blotch caused minor losses on susceptible cultivars. Tan spot was found in a few fields planted with minimum tillage and following a period of heavy rains; the first documented case of tan spot in the state. Tan spot probably occurs in a complex with St. nodorum, which causes similar symptoms. In 2001, as observed in 2000, a single grower in Georgia experienced a near total crop loss due to stinking smut; always a result of saving seed three or more consecutive years with no application of seed treatment. These rare instances have occurred as some growers attempt to cut costs to a minimum despite educational programs to prevent these unnecessary losses. BYDV was variable but generally low due to the cold weather during the autumn and early winter, which reduced aphid activity during the critical period for transmission and infection. We had a significant increase in dryland foot rot caused by Fusarium spp. This disease is more common in the western U.S. where wheat is grown under low rainfall conditions. The extended drought in Georgia over the past several years has favored the development of this disease. A number of fields were extensively damaged resulting in reduced yield and test weights below 55 lb/bu.
Hessian fly populations in winter wheat were predominantly biotype L in northern Georgia, but O is the dominant biotype in the southern part of the state. The H7H8 resistance genes remained effective in southern Georgia, but were only partly effective where biotype L was present. Advanced breeder lines containing H13 and H21 genes, which are effective against biotype L, were evaluated and screened for seed increase. An outbreak of true armyworm (Pseudaletia unipuncta) occurred throughout the southern U.S. in 2001. Armyworms defoliated wheat in Georgia during grain-filling but did not cause extensive grain-head clipping and apparent yield loss. Armyworms were controlled in heavily infested fields mostly using methyl parathion. Cereal leaf beetle (Oulema melanopus) populations continue to spread southward and increase in numbers in the upper coastal plain area of the state. Maize growing next to wheat fields was sometimes damaged as newly emerged adults moved from senescent wheat fields. Feeding damage by beetles usually was restricted to first 20 m of the field margin. Double-cropped cotton stands and yields were not adversely affect by planting into wheat stubble as compared with a fallow planting. Winter wheat stubble also did not increase insect numbers or disease incidence of cotton seedlings.