Canonical correlations between agronomic traits and seed physiological quality in segregating soybean populations.

The objective of this study was to evaluate the relationship between agronomic traits and physiological traits of seeds in segregating soybean populations by canonical correlation analysis. Seven populations and two commercial cultivars in three generations were used: F3 plants and F4 seeds; F4 plants and F5 seeds, and F4 seeds and plants. The following agronomic traits (group I) were evaluated: number of days to maturity, plant height at maturity, insertion height of first pod, number of pods, grain yield, and oil content. The physiological quality of seeds (group II) was evaluated using germination, accelerated aging, emergence, and emergence rate index tests. The results showed that agronomic traits and physiological traits of seeds are not independent. Intergroup associations were established by the first canonical pair for the generation of F3 plants and F4 seeds, especially between more productive plants with a larger pod number and high oil content and seeds with a high germination percentage and emergence rate. For the generation of F4 plants and F5 seeds, the first canonical pair indicated an association between reduced maturity cycle, seeds with a high emergence percentage and a high percentage of normal seedlings after accelerated aging. According to the second canonical pair, more productive and taller plants were associated with seed vigor. For the generation of F4 seeds and plants, the associations established by the first canonical pair occurred between seed vigor and more productive plants with high oil content and reduced maturity cycle, and those established by the second canonical pair between seeds of high physiological quality and tall plants.

Genetic divergence in a soybean (Glycine max) diversity panel based on agro-morphological traits.

Owing to the narrow genetic basis of soybean (Glycine max), the incorporation of new sources of germplasm is indispensable when searching for alleles that contribute to a greater diversity of varieties. The alternative is plant introduction, which may increase genetic variability within breeding programs. Multivariate techniques are important tools to study genetic diversity and allow the precise elucidation of variability in a set of genotypes of interest. The agro-morphological traits of 93 soybean accessions from various continents were analyzed in order to assess the genetic diversity present, and to highlight important traits. The experimental design was incomplete blocks (Alpha lattice, 8 x 12) with three replicates. Nine agro-morphological traits were analyzed, and principal component analysis and cluster analysis were performed, the latter by Ward's method. The dendrogram obtained contained eight subgroups, confirming the genetic diversity among the accessions and revealing similarities between 11 national genotypes. The geographical origin of the accessions was not always related to the clusters. The traits evaluated, and the methods used, facilitated the distinction and characterization of genotypes between and within groups, and could be used in Brazilian soybean breeding programs.

QTL mapping of soybean oil content for marker-assisted selection in plant breeding program.

The present study was undertaken to detect and map the quantitative trait loci (QTL) related to soybean oil content. We used 244 progenies derived from a bi-parental cross of the Lineage 69 (from Universidade Estadual Paulista "Júlio de Mesquita Filho"/Faculdade de Ciências Agrárias e Veterinárias - Breeding Program) and Tucunaré cultivar. A total of 358 simple sequence repeat (SSR; microsatellite) markers were used to investigate the polymorphism between the parental lines, and for the polymorphic lines all the F2 individuals were tested. Evaluation of the oil content and phenotype was performed with the aid of a Tango equipment by near infra-red reflectance spectroscopy, using single F2 seeds and F2:3 progenies, in triplicate. The data were analyzed by QTL Cartographer program for 56 SSR polymorphic markers. Two oil-content related QTLs were detected on K and H linkage groups. The total phenotypic variation explained by QTLs ranged from 7.8 to 46.75% for oil content. New QTLs were identified for the oil content in addition to those previously identified in other studies. The results reported in this study show that regions different from those already known could be involved in the genetic control of soybean oil content.