Seed weight (SW) is the important soybean (Glycine max [L.] Merr.), yield component and also affected the quality of soybean‐derived foods. The aim of this study was to identify the quantitative trait loci (QTL) underlying SW through 112 recombinant inbred lines (RILs) derived from the cross between “Zhongdou27” (G. max, designated by its bigger seed size, 21.9 g/100 seeds) and “Jiunong 20” (G. max, smaller seed size, 17.5 g/100 seeds). Phenotypic data were collected from this RIL population after it was grown in the sixteen tested environments. A total of eight QTL (QSW1‐1, QSW2‐1, QSW2‐2, QSW5‐1, QSW15‐1, QSW17‐1, QSW19‐1 and QSW20‐1) were identified, and they could explain 4.23%–14.65% of the phenotypic variation. Among these eight QTL, three QTL (QSW1‐1 located on the interval of Sat_159‐Satt603 of chromosome (Chr) 1 (LGD1a), QSW19‐1 located on the interval of Sat_340‐Satt523 of Chr 19 (LGL) and QSW20‐1 located on Sat_418‐Sat_105 of Chr 20 (LGI)) were newly identified and could explain 4.235%–10.08%, 8.45%–13.49% and 8.08%–10.18% of the phenotypic variation, respectively. Six of the eight identified QTL including QSW2‐2, QSW5‐1, QSW15‐1, QSW17‐1, QSW19‐1 and QSW20‐1 exhibited a significant additive (a) effect, while two QTL (QSW2‐1 and QSW19‐1) only displayed significant additive‐by‐environment (ae) effects. A total of four epistatic pairwise QTL for SW were identified in the different environments. These eight QTL and their genetic information obtained here were valuable for molecular marker‐assisted selection and the realization of a reasonable SW breeding programme in soybean.

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Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is the most important disease affecting yield of soybean (Glycine max (L.) Merr.). In China, among the main physiological races of SCN causing serious economic loss of soybean, HG Type 0 is the most widely distributed. Breeding SCN-resistant varieties is one of the safest and most effective ways to manage SCN. Soybean cv. Dongnong L-204 has a green seed coat and is a resource for resistance to SCN; however, the transcriptional variation and main molecular mechanism of resistance of Dongnong L-204 are not clear. We obtained 66.42 Gb of raw reads by using Illumina HiSeq high-throughput sequencing of Dongnong L-204. Transcriptional changes at Days 3, 7 and 10 after HG Type 0 stress are described. In total, 11279 differentially expressed genes were responsive to HG Type 0 stress, including 6407 SCN-induced and 4872 SCN-suppressed genes. Gene Ontology analysis emphasised the important roles of the terms metabolic process, single-organism process, catalytic activity and binding under HG Type 0 stress. Among them, the terms related to extracellular matrix, extracellular region part, membrane-enclosed lumen, protein-binding transcription factor activity, and symplast and cell junction existed only in pairwise comparisons Day 7 vs Day 0 and Day 10 vs Day 0. KEGG enrichment analysis showed that metabolic pathway played an important role in the stress response to HG Type 0. Cellular processes, metabolism and organismal systems and other pathway-related genes increased significantly after 7 days. Transcription factor analysis showed that transcription factors such as MYB, AP2-EREBP, bHLH, WRKY and NAC may be involved in the anti-HG Type 0 response of Dongnong L-204. At the same time, few transient inducible transcription factors were found and more transient inhibited transcription factors in Dongnong L-204 in the early stage of HG Type 0 syncytial establishment. RT-qPCR was used to analyse expression of 10 genes closely related to the HG Type 0 stress response. The expression of GmWRKYX1 was >60 times higher at Day 10 after HG Type 0 stress than at Day 0. The WRKY transcription-factor family may play an important role in the resistance of Dongnong L-204 to HG Type 0 stress.

Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is a common disease of soybean (Glycine max (L.) Merr.) worldwide, seriously affecting yield. Kangxian 2 is a soybean variety with a high level of resistance to H. glycines (HG) Type 0 (SCN race 3) and a yellow seed coat. However, we know little about the mechanism of resistance to HG Type 0 in Kangxian 2. In this study, we used the Illumina HiSeq high-throughput sequencing platform to analyse the transcriptome of Kangxian 2 and obtained 65.74 Gb clean data. Transcriptional changes in Kangxian 2 caused by HG Type 0 stress after 0–10 days are described. Kangxian 2 showed different levels of gene expression after inoculation, and under HG Type 0 stress after different times. Overall, 6854 HG Type 0-induced genes and 5328 HG Type 0-repressed genes were found to be differentially regulated. The greatest number of differential genes annotated to cellular process, metabolic process, single-organism process, binding, catalytic activity and other pathways. In addition to findings of differentially expressed genes similar to other published work, such as the regulation of biosynthesis of many secondary metabolites, carbon sequestration of photosynthetic organisms, other types of O-polysaccharide biosynthesis, phenylpropane biosynthesis, pyruvate metabolism and other pathways, this study also revealed the differential regulation of genes related to the diarylheptanoid and gingerol biosynthesis pathway and found some metabolic pathways that were specifically expressed in the syncytial initiation and establishment stages. Gene expression analyses using real-time fluorescence quantitative PCR showed that the expression of GmMADS and GmTUB changed strongly after 7 days and 10 days of HG Type 0 stress compared with the control. We conclude that GmMADS and GmTUB transcription factor genes may play an important role in the resistance of Kangxian 2 to HG Type 0 stress.