Tuesday, November 6, 2007
164-7
Growth Stage and Defoliation Stress: A Study of the Impact of Asian Soybean Rust on Yield Components.
Saratha Kumudini1, Claudia V. Godoy2, James E. Board3, and Joe Omielan1. (1) Plant & Soil Sciences, University of Kentucky, 1405 Veterans Drive Rm 425, Lexington, KY 40546-0312, (2) Embrapa - Soja, Rodovia Carlos Joao Strass, Caixa Postal 231, Londrina - PR, Brazil, (3) Louisiana State University Agricultural Center, Rm. 104 Sturgis Hall, Department of Agronomy & Environmental Mgmt, Baton Rouge, LA 70803
Soybean Rust (SBR) epidemics result in accelerated defoliation. Trials were planted in 2005 and 2006 in Brazil to test the hypothesis that defoliation is the primary cause of yield reductions due to SBR. A randomized complete block experiment with six replications was conducted in both years. Five treatments were established: i) SBR starting at growth stage R1, ii) SBR starting at growth stage R5, iii) mimic defoliation injury due to SBR at growth stage R1, iv) mimic defoliation injury due to SBR injury at growth stage R5, v) fungicide protection against SBR throughout development. Both yield and harvest index (HI) were reduced by SBR treatments. Mimicking defoliation injury by manual defoliation did not result in the same reductions in yield or HI as was observed in the diseased plots.