Genetic Analysis of Soybean Seed Response to Mechanical Damage
Sérgio Augusto Morais Carbonell and Natal Antonio Vello
Soybean (Glycine max (L.) Merrill) seed susceptibility to mechanical damage during harvesting,
threshing, and storage operations has decreased seed quality by reducing seed germination ability and seedling vigour, mainly in tropical and subtropical environments. This research aimed at estimating the genetic variability of seed response to mechanical damage (MD), and its relationship to agronomic characters such as plant height at maturity (PHM) and seed yield (SY). The material included 10 early maturity parents and 45 diallel crosses among them and five experimental checks. Ten F8:5 experimental lines from each cross were evaluated. The statistical and genetical analyses included estimates of phenotypic and genotypic correlations; relative contribution of genetic effects versus combined genetic and environmental effects; relationship between the genetical and experimental variation coefficients; coefficient of genotypic determination; expected and observed gain; and, correlated response to selection. The parents Paraná, Hale-321, IAC-Foscarin-31 and Primavera, showed the same MD resistance levels as IAS-5 cultivar, a standard check for MD resistance. The parents Palmetto, Coker-136, FT-81-1835 and Forrest were MD susceptible; however, they were superior to the IAC-2 cultivar, a standard check for MD susceptibility. The coefficient of genotypic determination for MD was estimated in 0.739, indicating large possibility to select MD resistant inbred lines in a population represented by the 45 diallel crosses. Expected and observed genetic gains indicated the possibility of success in the selection for resistance to MD among and within crosses. Based on the low genetic correlations (<0.25) among MD, PHM, and SY, all possible combinations of these traits could be found in a same soybean plant, at least in the early maturity group.
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