Salinity threatens soybean germination, growth and production.  The germination stage is a key period in the life of soybean.  Wild soybean contains many genes related to stress resistance that are valuable resources for the genetic improvement of soybean.  To identify the genetic loci of wild soybean that are active during seed germination under salt stress, two populations, a soybean interspecific hybrid population comprising 142 lines and a natural population comprising 121 wild soybean accessions, were screened for three germination-related traits in this study.  By using single-nucleotide polymorphism (SNP) markers with three salt tolerance indices, 25 quantitative trait loci (QTLs), 21 significant SNPs (–log₁₀(P)≥4.0) and 24 potential SNPs (3.5<–log₁₀(P)<4.0) were detected by linkage mapping and a genome-wide association study (GWAS) in two environments.  The key genetic region was identified based on these SNPs and QTLs.  According to the gene functional annotations of the W05 genome and salt-induced gene expression qRT-PCR analysis, GsAKR1 was selected as a candidate gene that responded to salt stress at the germination stage in the wild soybean.  These results could contribute to determining the genetic networks of salt tolerance in wild soybean and will be helpful for molecular marker-assisted selection in the breeding of salt-tolerant soybean.

The insensitive response to photoperiod and temperature is an important quantitative trait for soybean in wide adaptation breeding. The natural variation in response to photoperiod and temperature was detected using 275 accessions of soybean [Glycine max (L.) Merrill] from China. Genome-wide association mapping, based on population structure analysis, was carried out using 118 SSR markers by the TASSEL GLM (general linear model) program. Nine SSR markers (P<0.01) were associated with the value of the response to photoperiod and temperature (VRPT) caused by days to flowering (DF), among which, Satt308 (LG M), Satt150 (LG M) and Satt440 (LG I), were identified in both 2006 and 2007. Twelve SSR markers (P<0.01) were associated with VRPT caused by days to maturity (DM), among which three markers, Satt387 (LG N), Satt307 (LG C2) and AW310961 (LG J), were detected in both 2006 and 2007. In addition, a total of 20 elite alleles were screened out over 2006 and 2007 for being associated with an insensitive response to photoperiod and temperature (IRPT) caused by DF and a total of seven different elite alleles were screened out for being associated with IRPT caused by DM. Among these elite alleles, five alleles, Satt150-244, Satt308-164, Satt308-206, Satt440-176, and Satt440-206, were associated with IRPT caused by DF and were identified in both years, but only one allele, Satt307-170, was identified as being associated with an IRPT caused by DM. Based on these elite alleles, a set of typical accessions were screened out. The result about the genetic basis of IRPT is meaningful for soybean wide adaption breeding.

Cytoplasmic male sterility plays an important role in utilization of crop heterosis. Screening of soybean for novel genes related to male sterility in soybean could provide a basis for studying the molecular mechanism of male sterility in plants. In this study, gene differential expressions between the cytoplasmic male-sterile line NJCMS1A and its maintainer line NJCMS1B in soybean were analyzed using cDNA-AFLP. A differentially expressed fragment, GmMF-T4A15, was isolated from large flower buds of NJCMS1B. By searching the soybean genomic library and PCR amplification, the cDNA fulllength sequence of 1 311 bp was obtained and named GmMF1. The expression characteristics of GmMF1 were studied by semiquantitative real-time PCR and real-time quantitative PCR. The results showed that GmMF1 was expressed highly in flower buds of NJCMS1B. The deduced protein contains 436 amino acids and shows high similarity to members of the DUF620 protein family with unknown functions in other plant species. It is predicted that the protein encoded by GmMF1 is localized in the nucleus.