Gene pyramiding combinations confer resistance of Asian soybean rust

Pyramiding Rpp genes is a promising strategy to achieve a more durable resistance against Asian soybean rust (ASR). The objective of this study was to develop Rpp-pyramided populations and evaluate their resistance and yield in field conditions. Fifteen pyramided populations carrying different combinations of Rpp genes were developed, and the F-3 lines were evaluated to phenotypic resistance and yield performance. Our results suggest that the Rpp1-b of different resistant sources (PI 587880A, PI 594723, PI 4538A) have higher resistance and yield performance compared with other Rpp genes. Rpp-pyramided populations carrying two and three genes showed an increase in resistance compared with populations carrying a single Rpp gene. The best gene combinations were Rpp1-b + Rpp5, showing neither uredinia formation nor sporulation (immunity + RB1 phenotype reaction) in more than 70% of the F-3 population. Rpp-pyramided lines developed in this study have the potential to be used in backcross programs for improving ASR resistance.