Brown stem rot (BSR) of adzuki bean [Vigna angularis (Willd.) Ohwi & Ohashi], caused by Phialophora gregata (Allington et Chamberlain) W. Gams f. sp. adzukicola, is one of the most serious diseases of adzuki bean in Hokkaido. It is difficult to control BSR through chemical or cultural methods because BSR is soil-borne. The most effective means of controlling this disease is through the breeding of resistant cultivars. In 1996, a new race (race 2) of BSR was identified, which was virulent to all the commercial adzuki bean cultivars in Hokkaido. Therefore, greenhouse and field experiments were conducted to seek sources of resistance to BSR race 2. Field experiments consisted of two fields; one field mainly infested with BSR race 1 and the other with BSR race 2. Most adzuki bean cultivars previously selected for their resistance to BSR race 1 were susceptible to BSR race 2. Of 236 adzuki bean varieties and 36 wild adzuki bean accessions evaluated, one adzuki bean variety and one wild adzuki bean accession [Vigna angularis var. nipponensis (Ohwi) Ohwi & Ohashi] were found to be more tolerant to BSR race 2 than other adzuki bean germplasm accessions, based on both greenhouse and field evaluation. These two accessions, that were resistant to BSR race 1 and race 2, were selected as BSR resistance breeding gene sources. F₁ and F₂ hybrids between these resistant sources and susceptible sources were evaluated for the reaction to BSR race 2 in the greenhouse. The segregation ratio fitted to a 3 : 1 (resistant : susceptible) ratio, indicating that the newly selected gene sources resistant to race 2 were mainly controlled by a single dominant gene.

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In order to identify the effect of the brown pericarp and seed coat gene (colored gene), Rc on the antioxidant properties in brown rice, we examined T65Rc and its parental lines, P.T.B.10 and Taichung 65, using an isogenic line of the colored gene Rc. In the XYZ reaction oxygen scavenging emission system, the scavenging activity of hydrogen peroxide in the red rice varieties was 9 times as high as that of the rice variety Koshihikari (control). However, no significant differences in the antioxidant properties both in brown rice and germinated brown rice were observed between T65Rc and Taichung 65. The same results were obtained when the DPPH radical scavenging activity method was used. These results suggested that red rice exhibited a higher antioxidant activity than white colored rice, although the antioxidant activity of red rice was not affected by the colored gene Rc.

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To test the ability of germination in soil at low temperatures among rice cultivars, chicken-breasted seeds were sown under various temperature and depth conditions. Native red rice cultivars, Awa-akamai, Toyama-zairai-aka, Arozz da terra, Beni-roman, Khao mak fay, Khao louk kheuy and Myae shay displayed a higher ability than Koshihikari. In addition, the Germination rate index (GRI) of the seeds sown at a depth of 1.0 cm and grown at 15°C was a good index for the ability. Backcross inbred lines (BC₁F₂) with the genetic background of Koshihikari were made from Awa-akamai and Arozz da terra, respectively, and these lines were grown under the above-mentioned conditions. The backcross inbred lines made from Awa-akamai displayed a higher ability than those made from Arozz da terra. Linkage between the germination ability and pericarp color was not found in the Awa-akamai-derived lines. Therefore, Awa-akamai could be advantageous as a genetic resource in breeding for the improvement of germination in soil at low temperatures.

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