Characterization of soybean genotypes showing partial resistance to soybean rust

ABSTRACT Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is one of the most severe diseases that affect the crop. Among management strategies is the use of genotypes with horizontal or partial resistance, which are still restricted in the market but promising due to their resistance durability. The objective of this study was to evaluate the resistance of different genotypes to Asian soybean rust for future use in breeding programs. In the 2015/2016 crop season, 11 soybean genotypes from LAGER-UFU and cv. Desafio8473 (susceptibility pattern) were evaluated for artificial and natural infection by P. pachyrhizi in the field. ASR severity data were used to calculate the area under the disease progress curve (AUDPC). The percentage of affected leaf area and the AUDPC values of the evaluated genotypes ranged from 1.56 to 80.75% and from 380.62 to 975.62, respectively. The genotypes L-210, L-166, L-268, L-203, L-279, L-224, L-216 and L-218 have lower AUDPC values, indicating partial resistance, while the genotypes L-144, L-104, L-266 and cv. Desafio 8473 showed higher AUDPC values and therefore lower partial resistance or susceptibility. Even so, the genotypes L-144, L-104 and L-266 showed coefficients of disease severity progress 1.8 to 2.0-fold lower than those of cv. Desafio 8473. In conclusion, the genotypes from UFU Breeding Program (LAGER-UFU) showed potential to be used in the development of soybean cultivars resistant to P. pachyrhizi.