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Soil salinity is a major abiotic stress in agricultural production, as it hampers the growth and development of crop plants. Developing crop cultivars with salinity/salt tolerance is a major goal in many plant breeding programs. This study aimed to identify quantitative trait locus (QTL) that controls salt tolerance in the wild zombi pea (Vigna vexillata) accession "AusTRCF 322105." For QTL analysis, a BC1F2 population resulting from the cross between salt-susceptible TVNu240 and TVNu240 × AusTRCF 322105 was used. A genetic linkage map was constructed for the BC1F2 population, consisting of 15 linkage groups and using 296 SNP markers. The map spanned 2889.9 cM in total length. Plant leaf wilt and plant survival were evaluated by subjecting the BC1F2 population to a hydroponic condition with 250 mM NaCl to assess salt tolerance at the seedling stage. QTL analysis revealed that two QTLs, qSaltol_3.1 and qSaltol_7.1, control both leaf wilt and plant survival. These two QTLs explained 23–27% and 11–15% of the trait variation. Exploration of the physical genome region revealed that qSaltol_3.1 is located near genes encoding methionine sulfoxide reductase and protein L-isoaspartate O-methyltransferase that are involved in oxidative stress resistance. In contrast, qSaltol_7.1 is located near genes encoding 3-ketoacyl-CoA synthase, L-type lectin domain containing receptor kinase VII.1, lipoxygenase 3, CBS domain-containing protein 5, NAC25 protein, and asparagine synthetase (ASNS) that have been found to be associated with salt tolerance. Nonetheless, qSaltol_3.1 and qSaltol_7.1 are novel QTLs identified for salt tolerance in the zombi pea. [ABSTRACT FROM AUTHOR]

Key message: The major QTL Sdp1.1+ controlling seed dormancy in cowpea was finely mapped, and two CCoAOMT1 genes were identified as candidate genes for the dormancy. Seed dormancy in wild cowpea may be useful in breeding cultivated cowpea with pre-harvest sprouting resistance. A previous study identified a major quantitative trait locus (QTL) for seed dormancy, Sdp1.1+ , using the population of the cross between cultivated cowpea 'JP81610' and wild cowpea 'JP89083.' However, the molecular basis of seed dormancy in cowpea is not yet known. In this study, we aimed to finely map the locus Sdp1.1+ and identify candidate gene(s) for it. Germination tests demonstrated that the seed coat is the major factor controlling seed dormancy in the wild cowpea JP89083. Microscopic observations revealed that wild cowpea seeds, unlike cultivated cowpea seeds, possessed a palisade cuticle layer. Fine mapping using a large F2 population of the cross JP81610 × JP89083 grown in Thailand revealed a single QTL, Sdp1.1+ , controlling seed dormancy. The Sdp1.1+ was confirmed using a small F2 population of the same cross grown in Japan. The Sdp1.1+ was mapped to a 37.34-Kb region containing three genes. Two closely linked genes, Vigun03g278900 (VuCCoAOMT1a) and Vigun03g290000 (VuCCoAOMT1b), located 4.844 Kb apart were considered as candidate genes for seed dormancy. The two genes encoded caffeoyl coenzyme A O-methyltransferase 1 (CCoAOMT1). DNA sequencing and alignment of VuCCoAOMT1a and VuCCoAOMT1b between JP89083 and JP81610 revealed a single nucleotide polymorphism (SNP) causing an amino acid change in VuCCoAOMT1a and several SNPs leading to six amino acid changes in VuCCoAOMT1b. Altogether, these results indicate that VuCCoAOMT1a and VuCCoAOMT1b are candidate genes controlling physical seed dormancy in the wild cowpea JP89083. [ABSTRACT FROM AUTHOR]

Jatropha curcas (known as jatropha and physic nut) can be used as an alternative source for biodiesel and biomass production. However, conventional breeding of J. curcas needs time, labor and land for characterization and evaluation of the progenies owing to its perennial growth habit. Quantitative trait loci (QTL) mapping can help identifying marker-trait association and accelerate breeding process of perennial crops through marker-assisted selection. However, the genetic basis for woody biomass improvement in jatropha has not yet been studied. In this manuscript, we report the construction of a SNP-based linkage map and detection of QTLs for woody-biomass-related traits using an F2 population of the interspecific cross between J. curcas and Jatrophaintegerrima. A high-density genetic linkage map containing 2,179 SNPs was constructed. As high as 89.26% of the SNP markers developed from these interspecific progenies expressed significant segregation distortion. Most of the distorted markers showed neither gametophytic nor zygotic selection, except those on linkage groups 3, 5 and 6 which showed gametophytic and zygotic selection. The F2 population showed high variation and transgressive segregation for plant height, canopy width and wood density. QTL analyses detected 5, 8, and 7 loci for plant height, canopy width, and wood density, respectively. The SNPs linked to these QTLs could be incorporated into marker-assisted breeding to maximize the selection gain in jatropha biomass breeding. [ABSTRACT FROM AUTHOR]

The moth bean (Vigna aconitifolia), possibly the most primitive crop of the genus Vigna, is a highly drought- and heat-resistant legume grown in arid areas. Moth bean domestication involved phenotypic changes, including reduction of seed dormancy and pod shattering, increased organ size, and earlier flowering and maturity. However, the genetics of the domestication process in moth bean is not known. In this study, we constructed a genetic linkage map for moth bean and used the map to identify quantitative trait loci (QTL) for domestication-related traits of an F2 population of 188 individuals produced from a cross of wild moth bean (TN67) and cultivated moth bean (ICPMO056). The genetic linkage map comprised 11 linkage groups (LG) of 172 simple sequence repeat markers and spanned a total length of 1016.8 centiMorgan (cM), with an average marker distance of 7.34 cM. A comparative genome analysis showed high genome synteny between moth bean and mungbean (Vigna radiata), adzuki bean (Vigna angularis), rice bean (Vigna umbellata), and yardlong bean (Vigna unguiculata). In total, 50 QTLs and 3 genes associated with 20 domestication-related traits were identified. Most of the QTLs belonged to five LGs (1, 2, 4, 7, and 10). Key traits related to domestication such as seed dormancy and pod shattering were controlled by large-effect QTLs (PVE > 20%) with one or two minor QTLs, whereas all other traits were controlled by one–seven minor QTLs, apart from seed weight, which was controlled by one major and seven minor QTLs. These results suggest that a small number of mutations with large phenotypic effects have contributed to the domestication of the moth bean. Comparative analysis of QTLs with related Vigna crops revealed that there are several domestication-related large-effect QTLs that had not been used in moth bean domestication. This study provides a basic genetic map and identified genome regions associated with domestication-related traits, which will be useful for the genetic improvement of the moth bean and related Vigna species. [ABSTRACT FROM AUTHOR]

Zombi pea (Vigna vexillata) is a legume crop that is resistant to several biotic and abiotic stresses. Callosobruchus maculatus and Callosobruchus chinensis are serious stored-insect pests of legume crops. We constructed a high-density linkage map and performed quantitative trait loci (QTLs) mapping for resistance to these insect species in zombi pea. An F2 population of 198 individuals from a cross between 'TVNu 240' (resistant) and 'TVNu 1623' (susceptible) varieties was used to construct a linkage map of 6,529 single nucleotide polymorphism markers generated from sequencing amplified fragments of specific loci. The map comprised 11 linkage groups, spanning 1,740.9 cM, with an average of 593.5 markers per linkage group and an average distance of 0.27 cM between markers. High levels of micro-synteny between V. vexillata and cowpea (Vigna unguiculata), mungbean (Vigna radiata), azuki bean (Vigna angularis) and common bean (Phaseolus vulgaris) were found. One major and three minor QTLs for C. chinensis resistance and one major and one minor QTLs for C. maculatus resistance were identified. The major QTLs for resistance to C. chinensis and C. maculatus appeared to be the same locus. The linkage map developed in this study will facilitate the identification of useful genes/QTLs in zombi pea. [ABSTRACT FROM AUTHOR]