Maturity Group Classification and Maturity Locus Genotyping of Early-Maturing Soybean Varieties from High-Latitude Cold Regions

Abstract

BackgroundWith the migration of human beings, advances of agricultural sciences, evolution of planting patterns and global warming, soybeans have expanded to both tropical and high-latitude cold regions (HCRs). Unlike other regions, HCRs have much more significant and diverse photoperiods and temperature conditions over seasons or across latitudes, and HCR soybeans released there show rich diversity in maturity traits. However, HCR soybeans have not been as well classified into maturity groups (MGs) as other places. Therefore, it is necessary to identify MGs in HCRs and to genotype the maturity loci.MethodsLocal varieties were collected from the northern part of Northeast China and the far-eastern region of Russia. Maturity group reference (MGR) soybeans of MGs MG000, MG00, and MG0 were used as references during field experiments. Both local varieties and MGR soybeans were planted for two years (2010-2011) in Heihe (N 50°15′, E 127°27′, H 168.5 m), China. The days to VE (emergence), R1 (beginning bloom) and R7 (beginning maturity) were recorded and statistically analyzed. Furthermore, some varieties were further genotyped at four molecularly-identified maturity loci E1, E2, E3 and E4.ResultsThe HCR varieties were classified into MG0 or even more early-maturing. In Heihe, some varieties matured much earlier than MG000, which is the most early-maturing known MG, and clustered into a separate group. We designated the group as MG0000, following the convention of MGs. HCR soybeans had relatively stable days to beginning bloom from emergence. The HCR varieties diversified into genotypes of E1, E2, E3 and E4. These loci had different effects on maturity.ConclusionHCRs diversify early-maturing MGs of soybean. MG0000, a new MG that matures much earlier than known MGs, was developed. HCR soybean breeding should focus more on shortening post-flowering reproductive growth. E1, E2, E3, and E4 function differentially.

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

“…Nine accessions marked in S1 Table were also analyzed in a high latitude region of China [6]. Therefore, it was interesting to compare MG reference varieties with results in this study (Table 4).…”

“…Despite soybean being a typical short-day species it is successfully cultivated in long-day high latitude regions of North America, Europe and China [2], [6]. There are many reports suggesting that adaptation to certain environments is directly related to the relationship between flowering gene alleles and time to maturation of soybean [7], [21], [22].…”

“…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.…”

“…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].…”