Allelic Variations at Four Major Maturity E Genes and Transcriptional Abundance of the E1 Gene Are Associated with Flowering Time and Maturity of Soybean Cultivars

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.

Assessment of Soybean Flowering and Seed Maturation Time in Different Latitude Regions of Kazakhstan

“…The averaged data for triplicated trials were analyzed statistically for assessments of plant growth and yield components in three studied locations. The accessions were genotyped for E1 , E2 , E3 , and E4 alleles according to protocols published elsewhere [5], [19], [20], [14], respectively. DNA extraction and agarose gel electrophoresis were performed according to Abugalieva et al [17].…”

“…The productivity of soybean is largely dependent on flowering and maturity times in diverse ecological environments [2], [5], [6], [7]. Therefore, in Northern America 13 maturity groups (MG) were classified for breeding purposes [8].…”

“…Therefore, in Northern America 13 maturity groups (MG) were classified for breeding purposes [8]. The classification was found useful as it helped to compare patterns of seed maturation across many different environments [5], [6]. Soybean adaptability is primarily defined by expression of flowering genes [7], which may adjust duration of heading and maturity to maximize resource capture while minimizing the effect of abiotic stresses for specific environments.…”

“…Flowering genes have been assigned to a series ( E1-E8 ) [6], [9]. E1 , E2 , E3 , and E4 and their roles in flowering time and maturation have been characterized [9], [10], while the identity and function of E5-E8 genes remains largely unknown [5]. It was shown that E1-E4 genes are involved in regulation of both pre-flowering and post-flowering growth of plants under different photoperiod length [11].…”

Circadian Clock Genes Universally Control Key Agricultural Traits

“…Of these, the E1-E4 and E7 loci are responsible for photoperiodic control of flowering time (Watanabe et al, 2012;Zhai et al, 2014). Mapping of the E2/ FT2 locus showed that the responsible gene is GmGIa, a soybean homolog of AtGI (Watanabe et al, 2011).…”