II. 32. Reaction of Hordeum bulbosum L. to Japanese races of powdery mildew (Erysiphe graminis f. sp. hordei).
Ganesh Prasad,* S. Yasuda and T. Konishi, Institute for Agricultural and Biological Sciences, Okayama University, Kurashiki, Japan. "R"
* Present address: Dept. of Agri. Botany, Inst. of Advanced Studies, Meerut University, Meerut 250005, India.
Resistance to powdery mildew (Erysiphe graminis f. sp. hordei) races that attack H. vulgare L. is one of the desirable characters of H. bulbosum L. to be transferred to cultivated barley.
A total of six tetraploid strains of H. bulbosum, #191, #487, S-1, Turkey, S-15 and B-53, were chosen for study of their reaction to Japanese powdery mildew races I, IV and IX which were known to be practically most important in Japan, and besides, two induced tetraploid strains, Hosomugi and Hosogara, and a diploid cultivar, Kuromugi, were also taken as the susceptible check variety. Inoculation was done at two times--ll days and 13 days after sowing, and reaction was observed on the first leaf after 8 days of inoculation, followed by repeated observation after 2 days. Infection types were determined according to the extent of mycelium growth, sporulation and development of chlorosis/necrosis, and were classified into five grades (from 0 to 4) as indicated by Hiura (1960). Infection types 0, 0-1 and 1, 1-2 and 2, 2-3 and 3, and 3-4 and 4 represent immune, resistant, moderately resistant, moderately susceptible and susceptible, respectively.
The tetraploid strains, Hosomugi and Hosogara, and diploid cultivar Kuromugi were found to be susceptible to all the three mildew races. Reaction of H. bulbosum was as presented in Fig. 1. All of the six strains were found to have plants showing various reaction types to the mildew races. About 5% of S-15, #487 and S-1 were highly susceptible (reaction type 4) to the races I, IV and IX, respectively. The strain Turkey had a maximum proportion of highly resistant or immune plants, as compared to other strains.
Figure 1. Reaction of six strains of H. bulbosum to Japanese mildew races, I, IV and IX.
The present study also showed that H. bulbosum strains were more susceptible to powdery mildew races I and IV than to race IX. Frequency of plants showing immunity to race IX was also higher than those to race I and IV. It may be noted that in cultivated barley, most varieties from East Asia are resistant to race IX, differing from those in so-called Western regions (Takahashi et al. 1963). The results obtained here indicated that all the H. bulbosum strains consisted of individuals having different genotypes. In other words, they were highly heterogeneous for this character.
As to the resistance of H. bulbosum to powdery mildew, there are several reports differing in the results of reaction (Hardison, 1944; Eshed and Wahl, 1970; Jones and Pikering, 1978). The differences in the reactions may be attributed to several factors, such as H. bulbosum strain used, powdery mildew race, growth stage of the plant at the time of inoculation and environmental conditions. Since H. bulbosum is an out-breeding species, the population is heterogenous. Therefore, in planning to transfer disease resistance to cultivated barley, the desirable genotype should be isolated as the first step.
References:
Eshed, N. and I. Wahl. 1970. Host ranges and interrelations of Erysiphe graminis hordei, E. graminis tritici, and E. graminis avenae. Phytopath. 60:628-634.
Hiura, U. 1960. Studies on the disease-resistance in barley IV. Genetics of the resistance to powdery mildew. Ber. Ohara Inst. landw. Biol., Okayama Univ. 11:235-381.
Jones, I. T. and R. A. Pickering. 1978. The mildew resistance of Hordeum bulbosum and its transference into H. vulgare genotypes. Ann. Appl. Biol. 88:295-298.
Takahashi, R., J. Hayashi, S. Yasuda and U. Hiura. 1963. Characteristics of the wild and cultivated barleys from Afghanistan and its neighboring regions. Ber. Ohara Inst. landw. Biol., Okayama Univ. 12:1-23.
