Japanese Journal of Breeding

Resistance to the pathogens of snow mold, especially to Typhula ishikariensis S. Imai is one of the most important traits in wheat breeding for the central region of Hokkaido. T. ishikariensis always occurs in wheat nurseries when snow melts, at Hokkaido Natl.. Agric. Ext. Stn., where the snow mold resistance of winter wheat is being studied. Since T. ishikariensis consists of biotype A, B and C, it is considered that the resistance of winter wheat to each biotype should be determined. T. ishikariensis biotypes A, B and C which were cultured in a vermiculite-wheat bran medium were used as inoculum source. Five wheat varieties, PI 173438 (highly resistant), Horoshirikornugi (resistant), Takunekomugi (moderately resistant), Chihokukomugi (moderately susceptible) and lbis (susceptible) were treated with the inocula after the onset of a continuous snow cover in 1985 and 1986. In the plots inoculated with biotype A, PI 173438 always exhibited higher resistance to the fungi than the other varieties, but the damage of the wheat varieties inoculated with biotype B or C was so serious that the difference in resistance among the wheat varieties could not always be detected (Table 2, 3 and 4). Snow mold damage of wheat varieties inoculated with T.

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In Japan, protein content of malting barley is required to be between 9.5% and 11.5% by brewing industry, but the farmer's product of dominant cultivars often shows more than the upper limit of the range. Therefore, it is important to develop cultivars with a low protein content in barley breeding. In this paper the succesive changes of the characteristics relating to grain nitrogen accumulation were studied in the six rowed low-protein malting barley cv. Karl, together with its two rowed offsprings Daikei HC-1 and Daikei HC-2. The rate of increase of grain dry matter exhibits significant changes during the ripening period. Therefore the period was divided into three phases, Iag phase (LP), Iinear increase phase (LIP) and late filling phase (LFP) (Fig. 1). The ratio (dN/dW) of grain nitrogen increase (dN) to grain dry matter increase (dW) was higher in the LFP than in the LIP.

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Barley Yellow Mosaic Virus (BaYMV) is one of the most important virus in barley in Japan. UsUGI et al. (1985) identified BaYMV strain I and II based on their pathogenicity to two-rowed barley cultivars, Haruna Nijo and Amagi Nijo. Recently, an BaYMV isolated that infected two-rowed barley cultivar Misato Golden, resistant to strain I and II of BaYMV, was found at lbaraki prefecture and named as strain III. Based on field reactions of six barley indicator cultivars, fields where two-rowed barleys were planted for more than 3 years were found to be infested with strain I (Table 2). Fields where susceptible six-rowed barley cultivar, Kashimamugi, wa, s planted for more than four years or susceptible two-rowed barley cultivars were planted for less than two years were found to be infested with strain II (Table 2).

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A new soybean cultivar named Yumeyutaka, registered as Soybean Norin 97, was developed by the National Agriculture Research Center (NARC) in 1992. It is nearly isogenic to the widely grown cultivar Suzuyutaka, but differs in the lack of the two lipoxygenase isozymes, L-2 and L-3 in its seeds. Yumeyutaka was selected from a cross of a BC3F3 Iine lacking L-2, Suzuyutaka (4) x PI 86023 and a BC4F2 Iine lacking L-3, Suzuyukata (5) x Wasenatsu. The recurrent parent Suzuyutaka has all the lipoxygenase isozymes called L-1, L-2 and L-3, and is highly resistant to soybean mosaic virus (SMV) and moderately resistant to soybean cyst nematode (SCN). The donor parents PI 86023 and Wasenatsu are the mutant soybeans lacking L-2 and L-3, respectively. Yumeyutaka is similar to Suzuyutaka in all visible traits such as determinate stem, purple flower, gray pubescence, broad leaves, brown pods and dull whitish-yellow seeds with yellow hila of medium size. It is classified into the Maturity Group 111 . In performance trials in the fields of NARC and Tochigi Prefectural Experim.ent Station, the average seed yield during the period from 1989 to 1991 was 5% Iess than that of Suzuyutaka, while the protein and oil contents were similar to Suzuyutaka. It is resistant to SMV and SCN.

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