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Adzuki bean (Vigna angularis var. angularis), an important food legume, is grown in more than 30 countries, especially in East Asia. Almost 25% of the world population is affected by iron deficiency. Iron is very important on adzuki bean yield and quality. The identification of suitable reference genes in adzuki bean is important for exploring gene expression and the molecular mechanisms of gene, yet few reference genes have been reported for adzuki bean. This research systematically evaluated the stability of 11 candidate reference genes (ACT, ACT1, CYP, CYP2, SKIP16, ELF1B, HDC, Lectin, TUA, PEPKR1, and 18SrRNA) using the geNorm, NormFinder, BestKeeper, and RefFinder protocols under iron-deficient stress. The best combined number of reference genes for all samples was two. ELF1B/Lectin was best for qRT-PCR analysis of roots and combined analysis of roots, stems, and leaves under iron deficiency, ELF1B/CYP was optimum for leaves, and SKIP16/PEPKR1 was optimum for stems. The identification of these reference genes will enable accurate quantification of gene expression under iron deficiency and enhance our comprehension of reference genes in adzuki bean.

Recent archaeological findings provide a hint on domestication of azuki (Vigna angularis var. angularis) in East Asia. This preliminary study investigates archaeological collections from various regions in Korea, China, and Japan, representing the long-term evolution (5300–1450 BP) of azuki. Changes in seed shapes show that cultural manipulation of azuki began as early as 5300–4800 cal. BP. Azuki beans from Neolithic contexts in Korea and Japan show a possible sign of morphological response to human management, at least 2000 years prior to the appearance of fully domesticated forms. Yabutsuru-azuki (V. angularis var. nipponensis), a conspecific progenitor of domesticated azuki, has been a supplementary diet and seed reserve for lean years in East Asia, and this tradition may have a long root to the mid Holocene. Archaeological evidence indicates the possibility of multiple origins of azuki, supporting recent phylogenetic data. A unique contribution of this research is its interdisciplinary attempt to examine both the biological and cultural processes of this staple legume domestication.

To gain a better understanding of wild and weedy azuki population structures in relation to the cultigens we have developed simple sequence repeat (SSR) markers based on a new methodology for plant material. In the azuki bean genome, the number of (AG)n and (AC)n motif loci per haploid genome has been estimated to be 3,500 and 2,100, respectively, indicating that (AG)n motifs are a rich source of markers. We constructed a (AG)n-SSR-enriched library in azuki bean in order to obtain a comprehensive range of SSR markers efficiently. The method applied in this study resulted in a 116-fold enrichment over the non-enriched genomic library, with a high percentage (98%) of successful single-locus amplification by the primer pairs designed. Consequently, this method can be applied to construct SSR-enriched libraries suitable for large-scale sequencing. We obtained 255 unique sequences from an (AG)n-enriched library for azuki bean. Fifty primer pairs were designed and screened against five populations of wild azuki bean. Among these five populations, one population from Bato town, Tochigi prefecture, Japan, showed greater polymorphism using these primers than the others and was therefore chosen for the in-depth study. The genotypes of 20 individuals were investigated using eight of the SSR primers developed. The genetic relationships among individuals revealed a complex spatial pattern of population structure. Although azuki bean is considered to be a predominantly self-pollinating species, 3 of the 20 individuals tested in the population showed heterozygous genotypes, indicating outcrossing. Allele size and DNA sequence in each of the 20 individuals were compared with those of landraces and released cultivars of azuki bean. Plants in part of the population had many alleles of the same size and with the same sequence as those in cultivated azuki bean, suggesting that gene flow from the cultigen to wild plants has occurred in this population. Unintentional transgene escape from azuki could therefore occur when transgenic azuki is grown in areas where its wild and weedy relatives occur. The approach used here could be applied to biosafety monitoring of transgenic azuki bean.

BACKGROUND: Archaeobotany, the study of plant remains from sites of ancient human activity, provides data for studying the initial evolution of domesticated plants. An important background to this is defining the domestication syndrome, those traits by which domesticated plants differ from wild relatives. These traits include features that have been selected under the conditions of cultivation. From archaeological remains the easiest traits to study are seed size and in cereal crops the loss of natural seed dispersal. SCOPE: The rate at which these features evolved and the ordering in which they evolved can now be documented for a few crops of Asia and Africa. This paper explores this in einkorn wheat (Triticum monococcum) and barley (Hordeum vulgare) from the Near East, rice (Oryza sativa) from China, mung (Vigna radiata) and urd (Vigna mungo) beans from India, and pearl millet (Pennisetum glaucum) from west Africa. Brief reference is made to similar data on lentils (Lens culinaris), peas (Pisum sativum), soybean (Glycine max) and adzuki bean (Vigna angularis). Available quantitative data from archaeological finds are compiled to explore changes with domestication. The disjunction in cereals between seed size increase and dispersal is explored, and rates at which these features evolved are estimated from archaeobotanical data. Contrasts between crops, especially between cereals and pulses, are examined. CONCLUSIONS: These data suggest that in domesticated grasses, changes in grain size and shape evolved prior to non-shattering ears or panicles. Initial grain size increases may have evolved during the first centuries of cultivation, within perhaps 500-1000 years. Non-shattering infructescences were much slower, becoming fixed about 1000-2000 years later. This suggests a need to reconsider the role of sickle harvesting in domestication. Pulses, by contrast, do not show evidence for seed size increase in relation to the earliest cultivation, and seed size increase may be delayed by 2000-4000 years. This implies that conditions that were sufficient to select for larger seed size in Poaceae were not sufficient in Fabaceae. It is proposed that animal-drawn ploughs (or ards) provided the selection pressure for larger seeds in legumes. This implies different thresholds of selective pressure, for example in relation to differing seed ontogenetics and underlying genetic architecture in these families. Pearl millet (Pennisetum glaucum) may show some similarities to the pulses in terms of a lag-time before truly larger-grained forms evolved.

Summary Adzuki bean (Vigna angularis) is an important legume crop cultivated in over 30 countries worldwide. We developed a high‐quality chromosome‐level reference genome of adzuki bean cultivar Jingnong6 by combining PacBio Sequel long‐read sequencing with short‐read and Hi‐C technologies. The assembled genome covers 97.8% of the adzuki bean genome with a contig N50 of approximately 16 Mb and a total of 32 738 protein‐coding genes. We also generated a comprehensive genome variation map of adzuki bean by whole‐genome resequencing (WGRS) of 322 diverse adzuki beans accessions including both wild and cultivated. Furthermore, we have conducted comparative genomics and a genome‐wide association study (GWAS) on key agricultural traits to investigate the evolution and domestication. GWAS identified several candidate genes, including VaCycA3;1, VaHB15, VaANR1 and VaBm, that exhibited significant associations with domestication traits. Furthermore, we conducted functional analyses on the roles of VaANR1 and VaBm in regulating seed coat colour. We provided evidence for the highest genetic diversity of wild adzuki (Vigna angularis var. nipponensis) in China with the presence of the most original wild adzuki bean, and the occurrence of domestication process facilitating transition from wild to cultigen. The present study elucidates the genetic basis of adzuki bean domestication traits and provides crucial genomic resources to support future breeding efforts in adzuki bean.

The present paper deals with the report on the potential of Vigna angularis var. nipponensis (Ohwi) Ohwi and H. Ohashi assembled from Northeastern hill region (NEH) of India. The total of four exploration missions were conducted in remote and highaltitude areas of Nagaland, Arunachal Pradesh and Mizoram during 2011, 2016, 2017 and 2019 to confirm the occurrence, localities of new distribution and genetic resource study. Preliminary studies on seed germination and morpho-nutritional evaluation of seed of both cultivated and wild forms were also conducted. Conserving precious germplasm of this less represented wild relative of adzuki bean { Vigna angularis (Willd.) Ohwi and Ohashi} assumes great significance for its use in breeding and improvement of Vigna crop group.

BACKGROUND AND AIMS: The Asian genus Vigna, to which four cultivated species (rice bean, azuki bean, mung bean and black gram) belong, is suitable for comparative genomics. The aims were to construct a genetic linkage map of rice bean, to identify the genomic regions associated with domestication in rice bean, and to compare these regions with those in azuki bean. METHODS: A genetic linkage map was constructed by using simple sequence repeat and amplified fragment length polymorphism markers in the BC₁F₁ population derived from a cross between cultivated and wild rice bean. Using this map, 31 domestication-related traits were dissected into quantitative trait loci (QTLs). The genetic linkage map and QTLs of rice bean were compared with those of azuki bean. KEY RESULTS: A total of 326 markers converged into 11 linkage groups (LGs), corresponding to the haploid number of rice bean chromosomes. The domestication-related traits in rice bean associated with a few major QTLs distributed as clusters on LGs 2, 4 and 7. A high level of co-linearity in marker order between the rice bean and azuki bean linkage maps was observed. Major QTLs in rice bean were found on LG4, whereas major QTLs in azuki bean were found on LG9. CONCLUSIONS: This is the first report of a genetic linkage map and QTLs for domestication-related traits in rice bean. The inheritance of domestication-related traits was so simple that a few major QTLs explained the phenotypic variation between cultivated and wild rice bean. The high level of genomic synteny between rice bean and azuki bean facilitates QTL comparison between species. These results provide a genetic foundation for improvement of rice bean; interchange of major QTLs between rice bean and azuki bean might be useful for broadening the genetic variation of both species.

The effects of solid-state fermentation with Cordyceps militaris (L.) Fr. on the nutritional, physicochemical, and functional properties as well as angiotensin I converting enzyme (ACE) inhibitory activity of red bean (Phaseolus angularis [Willd.] W.F. Wight.) flour were determined. Fermentation increased the amount of small peptides but significantly decreased large peptides. Fermentation also increased proteins and essential amino acids (by 9.31 and 13.89%, respectively) and improved the in vitro protein digestibility (6.54%) of red beans. Moreover, fermentation increased the water holding capacity (from 2.36 to 2.59 mL/g), fat absorption capacity (from 84.65 to 114.55%), emulsion activity (from 10.96 to 52.77%), emulsion stability (from 5.43 to 53.82%), and foaming stability (from 11.95 to 20.68%). Fermented red bean flour achieved a lower least gelation concentration of 14% than that of the control (18%). In contrast to the non-fermented red bean, the fermented red bean showed ACE inhibitory activity, with IC50 value of 0.63 mg protein/mL. Overall, fermentation improved the nutritional, physicochemical, and functional properties as well as the biological activity of red bean flour. Thus, fermented red bean flour may serve as a novel nutritional and functional ingredient for applications in food design.

Genetic differences between azuki bean (Vigna angularis var. angularis) and its presumed wild ancestor (V. angularis var. nipponensis) were resolved into QTL for traits associated with adaptation to their respective distinct habits. A genetic linkage map constructed using progenies from a cross between Japanese cultivated and wild azuki beans covers 92.8% of the standard azuki bean linkage map. A reciprocal translocation between cultivated and wild azuki bean parents was identified on the basis of the linkage map having a pseudolinkage group and clustering of seed productivity-related QTL with large effect near the presumed breakpoints. In total, 162 QTL were identified for 46 domestication-related traits. Domestication of azuki bean has involved a trade-off between seed number and seed size: fewer but longer pods and fewer but larger seeds on plants with shorter stature in cultivated azuki bean being at the expense of overall seed yield. Genes found related to germination and flowering time in cultivated azuki bean may confer a selective advantage to the hybrid derivatives under some ecological conditions and may explain why azuki bean has evolved as a crop complex in Japan.

BACKGROUND: The objective of this study was to dissect into quantitative trait loci (QTLs) the large morphological and physiological differences between cultivated azuki bean (Vigna angularis) and a wild relative and to infer the commonalities of the QTLs for domestication-related traits across the Asian Vigna and with other warm-season legumes. METHODS: Two linkage maps, for the BC₁F₁ and F₂ populations, respectively, from the same cross between azuki bean and V. nepalensis were developed. Using these linkage maps QTLs for 33 domestication-related traits were analysed and mapped. The location of mapped QTLs was compared with locations of similar QTLs in other warm-season legumes. KEY RESULTS: QTLs were detected for seed-, pod-, stem- and leaf-related traits. Most traits were controlled by between two and nine QTLs but several traits, such as pod dehiscence, were controlled by single genes. QTLs for domestication-related traits were restricted to particular regions of the azuki bean genome, especially linkage groups 1, 2, 4, 7 and 9. Linkage groups 1 and 2 had QTLs for a suite of traits including pod size, germination, seed size and lower stem length. QTLs on linkage groups 7 and 9 were associated with upper stem length, maximum leaf size and pod and seed size. Pleiotropy or close linkage of genes for domestication-related traits is suggested in these regions. While some QTLs are common to azuki bean and other warm-season legumes, many are recorded for the first time in azuki bean. CONCLUSIONS: QTLs for a large number of domestication-related traits have been mapped for the first time in azuki bean. QTLs with unexpected effect and new QTLs for traits such as seed size have been found. The results provide a foundation that will be useful for improvement of azuki bean and related legumes.