title: Maturity group classification and maturity locus genotyping of early-maturing soybean varieties from high-latitude cold regions.
abstract: BACKGROUND
  With 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.
  
  
  METHODS
  Local 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  HCRs 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.
authors.affiliation: Ministry of Agriculture (MOA) Key Laboratory of Soybean Biology (Beijing), Institute of Crop Sciences, The Chinese Academy of Agricultural Sciences, Beijing, China; Heihe Branch of Heilongjiang Academy of Agricultural Sciences, Heihe, Heilongjiang, China.
authors.forename: Hongchang
authors.initials: H
authors.lastname: Jia
authors.affiliation: Ministry of Agriculture (MOA) Key Laboratory of Soybean Biology (Beijing), Institute of Crop Sciences, The Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Bingjun
authors.initials: B
authors.lastname: Jiang
authors.affiliation: Ministry of Agriculture (MOA) Key Laboratory of Soybean Biology (Beijing), Institute of Crop Sciences, The Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Cunxiang
authors.initials: C
authors.lastname: Wu
authors.affiliation: Heihe Branch of Heilongjiang Academy of Agricultural Sciences, Heihe, Heilongjiang, China.
authors.forename: Wencheng
authors.initials: W
authors.lastname: Lu
authors.affiliation: Ministry of Agriculture (MOA) Key Laboratory of Soybean Biology (Beijing), Institute of Crop Sciences, The Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Wensheng
authors.initials: W
authors.lastname: Hou
authors.affiliation: Ministry of Agriculture (MOA) Key Laboratory of Soybean Biology (Beijing), Institute of Crop Sciences, The Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Shi
authors.initials: S
authors.lastname: Sun
authors.affiliation: Heihe Branch of Heilongjiang Academy of Agricultural Sciences, Heihe, Heilongjiang, China.
authors.forename: Hongrui
authors.initials: H
authors.lastname: Yan
authors.affiliation: Ministry of Agriculture (MOA) Key Laboratory of Soybean Biology (Beijing), Institute of Crop Sciences, The Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Tianfu
authors.initials: T
authors.lastname: Han
mesh_terms: D016000:Cluster Analysis; D003081:Cold Climate; D060005:Genotyping Techniques; D063245:Plant Development / Q000235:genetics; D013025:Glycine max / Q000235:genetics* / Q000254:growth & development
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