Genetic diversity in Chinese soybean cultivars.

摘要

Broad and useful genetic diversity in soybean (Glycine max (L.) Merr.) is important in applied breeding to reduce vulnerability of soybean to pests as well as to promote breeding progress for yield and other agronomic traits. Genetic diversity in the commercial U.S. soybean cultivars; has been described as narrow and breeding progress for yield has not kept pace with increased field breeding effort in the past decade. Breeders have been searching for solutions to the problem. Chinese soybean cultivars are an untapped genetic reservoir that may help U.S. breeders address this issue.;Three hundred and forty-two ancestors were identified in the pedigrees of 651 Chinese cultivars. The genetic base of modern Chinese soybean breeding is larger than that of the U.S., with 35 and 340 ancestors contributing 50 and 90% of the genes to the 651 Chinese soybean cultivars, while only five and 26 ancestors contributed similar amounts to the U.S. base. The three major soybean growing regions, Northeastern (NEC), Northern (NQ and Southern (SC) have little soybean ancestry in common and constitute almost independent genetic bases.;A very low mean CP of 0.02 indicated the presence of a high level of genetic diversity compared to U.S. soybean and most other U.S. crops. Cultivar pools from the NEC, NC, and SC were genetically more distinct than are the midwestern and southern breeding pools of the U.S. Mean CP between the three regions were all less than 0.01. Contrasting provinces and cropping systems were also quite distinct in terms of low CP. The low CP values for Chinese soybean breeding likely result from continuing breeder initiatives to introduce new germplasm into applied Chinese breeding.;Multivariate analysis of phenotypic data transformed the 25 traits into 7 principal components which captured 79% of the total genotypic variation among the cultivars. The genetic similarity (GS) estimates were derived from principal component scores. The GS analysis separated Chinese and U.S. cultivar pools and clearly showed a much broader phenotypic diversity in Chinese than in U.S. cultivars. Cluster analysis of GS revealed seven distinct clusters, with almost all U.S. cultivars grouped into three. The general distinction of U.S. and Chinese cultivars is consistent with earlier findings based on CP. (Abstract shortened by UMI.).