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Poster Presentations


Poster Presentations


Effect of soybean Asian rust (Phakopsora pachyrhizi Syd.) severity on soybean yield

Presenter: Guy Mitsuyuki Tsumanuma(1)

Other authors and affiliations: Antonio Luiz Fancelli(1), Marco Antonio Tavares Rodrigues(2), Edson Begliomini(2). (1)ESALQ/USP, Crop Production, Piracicaba, Sao Paulo 13418-900, Brazil; (2)BASF-SA, Sao Paulo, Brazil

Field trials were carried out in 2006, with soybean (Glycine max (L.) Merrill) cultivars MG/BR 46 (Conquista) and BRS Valiosa RR, to evaluate the effect of soybean Asian rust on yield. The experimental design was complete randomized blocks with eight treatments and four replications with plots of 18 m2. Different times and numbers of applications of different groups of fungicides were used to generate a disease gradient. Disease severity and leaf area index were assessed weekly in 11 evaluations. Yield was estimated on central rows of the plots. The relationship between disease severity on different evaluations and the area under the disease progress curve (AUDPC) and yields were investigated. One program developed by Canteri et al. (2004) was utilized for AUDPC calculation. The AUDPC presented a negative linear correlation with yield (R2 = 0.9841 for “Conquista” and 0.9897 for “BRS Valiosa”). Disease severity at R6 (pods with full-sized green beans) and R7 (pods yellowing, 50% of leaves yellowing) presented a significant negative linear correlation with yield. For “Valiosa” the best correlation was observed in R6 (R2 = 0.994), whereas for “Conquista”, it was in R7 (R2 = 0.996).

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