The Genetics of Domestication of the Azuki Bean (Vigna angularis)

Abstract

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.

QTLs CONTROLLING SEED WEIGHT AND DAYS TO FLOWERING IN MUNGBEAN [Vigna radiata (L.) Wilczek], THEIR CONSERVATION IN AZUKI BEAN [V. angularis (Ohwi) Ohwi & Ohashi] AND RICE BEAN [V. umbellata (Thunb.) Ohwi & Ohashi]

“…Mungbean, azuki bean and rice bean belong to the subgenus Ceratotropis which are known as Asian Vigna because they are all originated in Asia. QTLs for seed weight and flowering time have been reported in azuki bean (Isemura et al, 2007;Kaga et al, 2008) and rice bean (Isemura et al, 2010). Comparison of QTL locations for seed weight and flowering time of mungbean in the present study with those of azuki bean and/or rice bean (Figure 3) further supports previous findings.…”

Pod Shattering: A Homologous Series of Variation Underlying Domestication and an Avenue for Crop Improvement

“…Genetic analysis of pod shattering has been carried out in various legumes including soybean [48,[93][94][95][96][97][98][99][100][101], common bean [13,44], pea [18,50,102], cowpea [49,[103][104][105][106], lentil [16,46,107], narrow-leaf lupin [47,108], azuki bean [45,109], and common vetch [43,110]. In most of the legumes that have been studied so far, pod shattering is found to be a dominant trait controlled by one or two genes or QTLs (Table 1).…”

“…In common vetch, Vicia sativa, shattering was found to be controlled by a single gene, and recessive mutants were selected during domestication for their non-shattering character [43]. Similar to common vetch, a single gene controls the shattering process in azuki bean, Vigna angularis [45,109]. In narrow-leafed lupin (Lupinus angustifolius), two genes are involved in controlling the recessive non- shattering trait [108].…”

“…Several studies demonstrated shattering resistance can be gained by mutations in a single locus (common vetch [43]; common bean [44]; azuki bean [45]; lentil [46]), or in two loci (narrow-leaf lupin [47]; soybean [48]; cowpea [49]; pea [50]). Throughout the domestication process, strong selection of these loci leads to the fixation of non-shattering trait in crop plants [33], and consequently, a number of modern cultivars have indehiscent pods.…”

Control of volunteer adzuki bean in soybean

“…Adzuki bean pods shatter easily [3], which leads to significant seed losses prior to and during harvest. The seed coat of adzuki beans is hard in comparison to soybean and other legumes, reducing permeability to water and increasing the longevity of seed viability in the soil [4]. Anecdotally, growers have remarked that the presence of volunteer adzuki bean plants can still be an issue even 10 years after the last crop was grown.…”