Construction of Linkage Maps Using DNA Markers and Mapping of Useful Genes in Azuki Bean

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The construction of a linkage map is of fundamental importance for the efficient exploration of plant genetic potential. Molecular linkage map will facilitate genetic mapping, gene tagging and improved selection in breeding program. Therefore, in the present study, the followings were carried out to obtain the basic information on further molecular breeding of azuki bean (Vigna angularis, 2n=22). 1. Two azuki linkage maps were constructed with F_2 populations derived from the interspecific crosses between azuki bean and its wild relative, V.nakashimae, and between azuki bean and rice bean (V.umbellata). The former map consisted of 14 linkage groups with 108 RAPD and 19 RFLP markers and the total map size was 1250 cM.The latter contained 14 linkage groups with 74 RAPD and 114 RFLP markers covering 1702 cM.2. The conserved linkage blocks were identified between these two azuki interspecific maps and mungbean (V.radiata) map based on the lineage of the common mapped markers. 3. Morphological markers and QTLs were mapped in the azuki linkage maps. Five major genes controlling morphological characters, such as epicotyl color, pod color and pod shattering, were mapped in the interspecific map between azuki bean and V.nakashimae. The locations of one major gene for epicotyl color and several QTLs (days to heading, plant height, seed weight, bruchid resistance, etc...) were estimated in azuki-rice bean map. 4. Production of recombinant inbred lines from the cross between azuki bean and rice bean is now in progress to determine the precise locations of QTLs.