Genetic analysis of tolerance to aluminum toxin at seedling stage in soybean based on major gene plus polygene mixed inheritance model

The segregation analysis based on major gene plus polygene mixed inheritance model was employed to study the inheritance of aluminum (Al) tolerance in soybean. A recombinant inbred line (RIL) population derived from a cross between Al-tolerant (KF No.1) and Al-sensitive (NN 1138-2) parents along with both parents was analyzed using phenotypic data of three traits, i.e. relative total plant dry weight (RTDW), relative shoot dry weight (RSDW) and relative root dry weight (RRDW) assayed in sand culture. Significant difference among RILs was observed, and frequency distributions showed characteristics of mixed distributions, which suggested that inheritance of Al tolerance conformed to major gene plus polygene mixed inheritance model. The results indicated that the genetic model type I (four additive major genes plus additive polygenes) was the most fitting one for the traits, indicating some common genetic mechanism lying among the traits, though their respective best fitting models were somewhat different, i.e. I-6, I-9 and I-8 for RTDW, RSDW and RRDW, respectively, within model type I. It supports to choose RTDW as the representative for Al tolerance evaluation in addition to its virtue of being the whole-plant trait and easy to measure in sand culture. Averagely, the major genes contributed about 50%, while the collective polygenes contributed about 30% to the phenotypic variation, indicating both being important in breeding for Al tolerance. The study recommends that the segregation analysis can be used by soybean breeders who have accumulated abundant segregation data to obtain preliminary information on the inheritance of their breeding materials, and can be used as a first screening for presence of major genes followed with molecular marker analysis to further confirm and locate the major genes of quantitative traits.