The growing global demand for products associated with the soybean complex, the expansion in area cultivated with soybean tolerant to the herbicide glyphosate (Roundup Ready ®) and the advent of Asian soybean rust as a devastating disease in Brazil has increasing the need of soybean elite cultivars with resistance/tolerance to rust and transgenic technology. The objective of this research is to evaluate the reaction to rust from crosses of transgenic and conventional soybean, by observing the performance of their progenies. The genetic materials include the F2:5 and F2:6 progenies derived from 20 crosses (10 progenies / cross) between parents with high oil yield USP 70.108, USP 70.010, USP 70.113, USP 70.007 and USP 70.042 with conventional cultivars (BRS 133 and Conquista) and its essentially derived transgenic versions (BRS 245 RR and BRS Valiosa RR). The experiments involve two types of management with herbicides, conventional management for conventional soybean and glyphosate-based management for RR soybean, and two types of management of fungicides, an experiment with successive applications of Opera & Native (fungicides that control rust and Late Season Leaf Diseases or DFC) and another experiment with applications of Derosal (fungicide that controls only the DFC). The evaluated traits are the seed yield (PG), one hundred seed weight (PCS), the rate of reaction to rust on seed yield (TRFP) and rate of reaction to rust on seed size (TRFT). The genetic-statistical analyzes will use the computer programs SAS and R and the diallel analysis will be based on method 2 (fixed model) of Griffing. The reactions of soybean genotypes to rust will be compared in the two technologies (conventional and transgenic crosses with and without the transgene RR managements and herbicides) by means and estimates of combining ability parameters. The parameter estimates will be important for designing the next steps of selection in field experiments.
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