In order to identify genes for field resistance to rice blast in the upland rice variety Sensho, analysis of quantitative trait loci (QTLs) was performed by using F₂ plants/F₃ lines derived from a cross between Sensho and a paddy rice cultivar Norin 29. Resistance to rice leaf blast was measured at an upland nursery. The disease severity was scored by visual observation. Continuous variations were observed and it was suggested that several genes were involved in the resistance to leaf blast in Sensho. Four QTLs were detected in the vicinity of restriction fragment length polymorphism (RFLP) markers G271 (chromosome 4), G177 (chromosome 4), C1172 (chromosome 11) and S826 (chromosome 12), respectively. QTLs near RFLP markers G271, G177, C1172 and S826, explained about 45%, 13%, 8% and 8% of the phenotypic variation in the F₃ lines, respectively. For all of the QTLs, alleles from Sensho increased the score of resistance to rice leaf blast.

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RAPD analysis was carried out to elucidate the genetic variation of 203 azuki bean landraces from Japan, South Korea, China, Taiwan, Bhutan and Nepal. In total, 413 distinct bands were amplified using 48 primers. Of these, 97 bands were found to be polymorphic. Most of the landraces could be identified individually using these RAPD markers. Based on a simple matching coefficient using 97 polymorphic bands, average dissimilarities of landraces between regions were larger than those within regions. Particularly, large genetic differences were observed between the landraces in the Bhutan-Nepal region and those in Japan (0.615), and between the Bhutan-Nepal and Korea-China-Taiwan groups (0.598). Based on the dissimilarities between the landraces, cluster analysis was carried out by the UPGMA method, and 203 landraces were mainly classified into the groups that reflected the collection origin. These results suggested that azuki bean seeds had not been frequently exchanged between the regions in the past. In this study, the following conclusions were reached: Large genetic variation among landraces can be applied for the azuki bean breeding by expanding the genetic base of cultivars. Molecular linkage map can be constructed with the intraspecific populations derived from the cross between the landraces in the Bhutan-Nepal and East Asia regions.

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