Genetics of seed abortion and reproductive traits in soybean

In soybean [Glycine max (L.) Merr.], yield or seed number is determined by the number of seeds per pod, the number of pods per plant, and the number of plants per row. Seeds per pod is a function of the number of ovules per pod and the success of seed set (lack of seed abortion). The objective of this study was to define the genetic basis for seed set. In this study, recombinant inbred (RI) segregants of soybean have been used to identify genetic components, quantitative trait loci (QTLs) that regulate different parameters of seed set. The numbers of ovules per pod and abortions were measured in RI segregants of soybean, as were positions and developmental stages of abortions within pods. Quantitative trait loci were identified from segregants of the Minsoy-Noir 1 RI population grown in Utah and Minnesota. These were confirmed in Minsoy-Archer or Noir 1-Archer RI populations grown in Minnesota. The average abortion frequency in the three RI populations ranged from 10 to 29%. Abortions occurred most frequently in the basal position of the pod and embryo development ceased most often at one of two developmental stages: embryos failed to develop (or ovules were not fertilized), or embryos were partially developed and ceased growth just after cotyledon differentiation. Quantitative trait loci were found on several linkage groups, including U11, U13, and U22. The QTLs in U11 were linked to QTLs for flowering date, reproductive period (RP), and maturity. Two separate QTLs on U13 were linked to genes for male and female sterility (Ms1, Ms6, or St5) and to genes for disease resistance, respectively. One of two distinct QTLs on U22 was associated with a previously identified QTL for water use efficiency. Also of interest was a QTL on U3 linked to Lf1 that determined the number of ovules per pod, suggesting a common regulation of leaf and flower primordia.