Assessing tolerance to Asian soybean rust in soybean inbred lines from exotic and adapted crosses

Abstract

Asian soybean rust (ASR) is one of the most important diseases in soybean and is responsible for large economic losses. However, the use of tolerant genotypes is a sustainable strategy to address this issue. The aims of this study were to evaluate the tolerance to ASR across agronomic traits and to characterize the genetic control of the tolerance to this disease. We evaluated 257 inbreed lines from North Carolina Design II between four exotic parents and five adapted ones over F5:6 and F5:7 generations in management practices with and without ASR control. The traits seed yield (SY), hundred-seed weight (HSW), number of days to maturity (NDM), plant height at maturity, and agronomic value (AV) were considered to perform the rust difference (RD) index, analysis of variance, combining ability, and correlations. The SY, HSW, and NDM were significant to the line × management interaction, enabling selection for tolerance, and 44.7% of the lines demonstrated simultaneous tolerance to these traits based on the RD significance parameter. The correlations between the RD indices were nonsignificant with the exception of the RD for SY and AV. Our results suggest that the SY for the inbred lines is controlled by additive and parental additive-by-additive epistatic effects, while the tolerance for the SY is controlled by recombinant additive-by-additive epistatic effects. In addition, the results indicate that tolerance to Asian soybean rust occurs with different traits that are independent from one another. Therefore, tolerance should be addressed using a multitrait approach.