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Soil salt-alkalization seriously impacts crop growth and productivity worldwide. Breeding and applying tolerant varieties is the most economical and effective way to address soil alkalization. However, genetic resources for breeders to improve alkali tolerance are limited in mung bean. Here, a genome-wide association study (GWAS) was performed to detect alkali-tolerant genetic loci and candidate genes in 277 mung bean accessions during germination. Using the relative values of two germination traits, 19 QTLs containing 32 SNPs significantly associated with alkali tolerance on nine chromosomes were identified, and they explained 3.6 to 14.6% of the phenotypic variance. Moreover, 691 candidate genes were mined within the LD intervals containing significant trait-associated SNPs. Transcriptome sequencing of alkali-tolerant accession 132–346 under alkali and control conditions after 24 h of treatment was conducted, and 2565 DEGs were identified. An integrated analysis of the GWAS and DEGs revealed six hub genes involved in alkali tolerance responses. Moreover, the expression of hub genes was further validated by qRT-PCR. These findings improve our understanding of the molecular mechanism of alkali stress tolerance and provide potential resources (SNPs and genes) for the genetic improvement of alkali tolerance in mung bean.

Salt-alkaline stress generally leads to soil compaction and fertility decline. It also restricts rice growth and nutrient acquisition, so reduces rice yield. However, little is known about the effect of salt-alkaline stress on the carbon and nitrogen metabolism of rice. In this study, two relatively salt-alkaline tolerant (Changbai 9 and Dongdao 12) and sensitive (Jinongda 138 and Tongyu 315) rice cultivars were grown in a field experiment conducted with two soil types including black soil and salt-alkaline soil to evaluate the characteristics of yield, carbon and nitrogen metabolism in rice. Results showed that yield and nitrogen use efficiency (NUE) in rice greatly decreased under salt-alkaline stress. Changbai 9 (CB9) and Dongdao 12 (DD12) showed higher NUE than Jinongda 138 (JND138) and Tongyu 315 (TY315) under the salt-alkaline stress. Additionally, carbon and nitrogen metabolism enzyme activity and compound content were significantly affected by salt-alkali stress; different performances were observed between cultivars under salt-alkaline stress. In conclusion, our results indicate that salt-alkaline tolerant rice cultivars may have more stable carbon and nitrogen metabolism than sensitive genotypes under salt-alkaline conditions.

Tetrastigma hemsleyanum Diels & Gilg ex Diels is a liana plant with promising medicinal and ornamental values. Its calabash-shaped roots (CRs) are served as a traditional Chinese herb. However, it takes a long growth period to form CRs. In this study, three types of architectural roots, including fibrous roots (FRs), bar-shaped roots (BRs) and CRs, were employed as materials, and the characteristics of histo-anatomy and digital RNA-seq transcriptome profiles were analyzed. Among the three types of roots, the vascular bundles in FRs were intact, while some of the vascular bundles degenerated in BRs, and only few traces of vascular bundles existed in CRs. Meanwhile, no obvious cell inclusions were found in the cytoplasm of FRs, while a few inclusions were found in BRs, and abundant inclusions were detected in CRs, which might be the main source of medicinal components in roots. The transcriptome profiles and qRT-PCR validation indicated that seven upregulated genes, encoding xyloglucan glycosyltransferase, ACC oxidase, CYP711A1, SHORT-ROOT transcript factor, galacturonosyltransferas, WAT1 and WRKY, and two downregulated genes, encoding LRR receptor-like serine/threonine-protein kinase and CYP83B1, were probably involved in the formation and development of CRs. In addition, Gene Ontology terms of intrinsic component of membrane, integral component of membrane, cell periphery, membrane part, plasma membrane, membrane, intrinsic component of plasma membrane, cellular chemical homeostasis and plasma membrane part were probably related to the formation of CRs. Kyoto Encyclopedia of Genes and Genomes pathways related to the development of CRs probably included MAPK signaling pathway–plant, plant hormone signal transduction and circadian rhythm–plant. Our finding suggested a probable mode for the formation of CRs.