Characterization of Pingliang xiaoheidou (ZDD 11047), a soybean variety with resistance to soybean cyst nematode Heterodera glycines.

KEY MESSAGE: A novel QTL (qSCN-PL10) for SCN resistance and related candidate genes were identified in the soybean variety Pingliang xiaoheidou, and plant basal immunity seems to contribute to the SCN resistance. Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is one of the most devastating soybean pests worldwide. The development of host plant resistance represents an effective strategy to control SCN. However, owing to the lack of diversity of resistance genes in soybean varieties, further investigation is necessary to identify new SCN resistance genes. By analyzing the resistance phenotypes of soybean variety Pingliang xiaoheidou (Pingliang, ZDD 11047), we found that it exhibited the different resistance phenotypes from PI 88788 and Peking varieties. Because Pingliang variety contains the Rhg1-a (low copy) haplotype and lacks the resistant Rhg4 haplotype, novel quantitative trait locus might account for their SCN resistance. After sequencing parental lines (Magellan and Pingliang) and 200 F2:3 progenies, a high-density genetic map was constructed using the specific length amplified fragment sequencing method and qSCN-PL10 was identified as a novel locus for SCN resistance. Candidate genes were predicted by RNA sequencing (RNA-seq) in the qSCN-PL10 locus region. The RNA-seq analysis performed also indicated that plant basal immunity plays an important role in the resistance of Pingliang to SCN. These results lay a foundation for the use of marker-assisted breeding to enhance the resistance to SCN.

RNA-Seq analysis of nodule development at five different developmental stages of soybean (Glycine max) inoculated with Bradyrhizobium japonicum strain 113-2.

Nodule development directly affects nitrogen fixation efficiency during soybean growth. Although abundant genome-based information related to nodule development has been released and some studies have reported the molecular mechanisms that regulate nodule development, information on the way nodule genes operate in nodule development at different developmental stages of soybean is limited. In this report, notably different nodulation phenotypes in soybean roots inoculated with Bradyrhizobium japonicum strain 113-2 at five developmental stages (branching stage, flowering stage, fruiting stage, pod stage and harvest stage) were shown, and the expression of nodule genes at these five stages was assessed quantitatively using RNA-Seq. Ten comparisons were made between these developmental periods, and their differentially expressed genes were analysed. Some important genes were identified, primarily encoding symbiotic nitrogen fixation-related proteins, cysteine proteases, cystatins and cysteine-rich proteins, as well as proteins involving plant-pathogen interactions. There were no significant shifts in the distribution of most GO functional annotation terms and KEGG pathway enrichment terms between these five development stages. A cystatin Glyma18g12240 was firstly identified from our RNA-seq, and was likely to promote nodulation and delay nodule senescence. This study provides molecular material for further investigations into the mechanisms of nitrogen fixation at different soybean developmental stages.