Abstract
The time to flowering and maturity are ecologically and agronomically important traits for soybean landrace and cultivar adaptation. As a typical short-day crop, long day conditions in the high-latitude regions require soybean cultivars with photoperiod insensitivity that can mature before frost. Although the molecular basis of four major E loci (E1 to E4) have been deciphered, it is not quite clear whether, or to what degree, genetic variation and the expression level of the four E genes are associated with the time to flowering and maturity of soybean cultivars. In this study, we genotyped 180 cultivars at E1 to E4 genes, meanwhile, the time to flowering and maturity of those cultivars were investigated at six geographic locations in China from 2011 to 2012 and further confirmed in 2013. The percentages of recessive alleles at E1, E2, E3 and E4 loci were 38.34%, 84.45%, 36.33%, and 7.20%, respectively. Statistical analysis showed that allelic variations at each of four loci had a significant effect on flowering time as well as maturity. We classified the 180 cultivars into eight genotypic groups based on allelic variations of the four major E loci. The genetic group of e1-nf representing dysfunctional alleles at the E1 locus flowered earliest in all the geographic locations. In contrast, cultivars in the E1E2E3E4 group originated from the southern areas flowered very late or did not flower before frost at high latitude locations. The transcriptional abundance of functional E1 gene was significantly associated with flowering time. However, the ranges of time to flowering and maturity were quite large within some genotypic groups, implying the presence of some other unknown genetic factors that are involved in control of flowering time or maturity. Known genes (e.g. E3 and E4) and other unknown factors may function, at least partially, through regulation of the expression of the E1 gene.
Highlights
It is generally considered that soybean has been domesticated in China for several thousand years [1]
This system has been practically used for several decades in soybean breeding and soybean production, assignment of a cultivar into a maturity group is time-consuming, and is sometimes hard due to the ambiguous phenotypic data [5]
The aims of this study were to investigate the extent to which the genetic variation at E1 through E4, as well as expression of the E1 gene could explain the phenotypic variation of the time to flowering and maturity for cultivars collected from different soybean growing areas in China
Summary
It is generally considered that soybean has been domesticated in China for several thousand years [1]. MG 000, MG 00, and MG 0 are the earliest maturity cultivars and are mainly distributed in production areas of the southern Canada [4], while MG I and MG II are typically grown in the northern region of the USA, the rest of the groups are succeedingly grown further south [5]. This system has been practically used for several decades in soybean breeding and soybean production, assignment of a cultivar into a maturity group is time-consuming, and is sometimes hard due to the ambiguous phenotypic data [5]
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