Abstract
The mini core collection (MCC) has been established by streamlining core collection (CC) chosen from China National Genebank including 23,587 soybean (Glycine max) accessions by morphological traits and simple sequence repeat (SSR) markers. Few studies have been focused on the maturity that has been considered as one of the most critical traits for the determination of the adaptation-growing region of the soybean. In the current study, two hundred and ninty-nine accessions of MCC planted for two years at four locations namely in Heihe, Harbin, Jining and Wuhan cities in China were used to assess the variation of maturity in MCC and identify the integrated effect of 4 E loci on flowering and maturity time in soybean. Forty-two North American varieties served as references of maturity groups (MG). Each accession in MCC was classified by comparing with the MG references in the days from VE (emergence) and physiological maturity (R7). The results showed that MCC covered a large range of MGs from MG000 to MGIX/X. Original locations and sowing types were revealed as the major affecting factors for maturity groups of the MCC accessions. The ratio of the reproductive period to the vegetative period (R/V) varied among MCC accessions. Genotyping of 4 maturity genes (i.e. E1, E2, E3 and E4) in 228 accessions indicated that recessive alleles e1, e2, e3 and e4 promoted earlier flowering and shortened the maturity time with different effects, while the dominate alleles were always detected in accessions with longer maturity. The allelic combinations determined the diversification of soybean maturity groups and adaptation to different regions. Our results indicated that the maturity of Chinese soybean MCC showed genetic diversities in phenotype and genotype, which provided information for further MG classification, geographic adaptation analysis of Chinese soybean cultivars, as well as developing new soybean varieties with adaptation to specific regions.
Highlights
China has the richest germplasm resources of soybean in the world[1]
As the accessions number of the CC is too large for the replicated evaluations at different locations, more manageable mini core collections (MCCs) of soybean have been developed based on further streamlining of the CC scale (10% of the CC), which represented 94.5% of the phenotypic diversity and 63.5% of the genetic diversity of the whole collection, respectively[11,12]
The growth duration of MG000 to MG0 reference varieties planted in Heihe was longer than that in Jining (82–115 days vs. 61–80 days)
Summary
China has the richest germplasm resources of soybean in the world[1]. More than 23,587 soybean accessions had been collected from 29 provinces of China until 2007[2]. Evaluation of soybean germplasm collection is crucial for the selection of elite parents, identification of desirable alleles, as well as breeding of new varieties[3,4,5]. As the accessions number of the CC is too large for the replicated evaluations at different locations, more manageable mini core collections (MCCs) of soybean have been developed based on further streamlining of the CC scale (10% of the CC), which represented 94.5% of the phenotypic diversity and 63.5% of the genetic diversity of the whole collection, respectively[11,12]
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