抵抗性の異なる品種におけるコムギから黒穂病菌感染の差異

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1. Using three wheat varieties, Norin No.50 (susceptible), Norin No.61 (moderately resistant), and Yuyake-komugi (resistant), the mode of disease appearence of flag smut (Urocystis tritici Koern.) was examined, when soil temperature was regulated at 5, 10, 15, 20, and 25℃, respectively, during 24 days after the seeds were inoculated with the fungal spores and sown in sterilized soil. In Norin No.50, 98 to 99 per cent of the plants were diseased at 10 to 20℃. In most cases, main culms showed symptoms, and 96 to 98 percent of tillers of the diseased plants were also smutted. At 25℃ and 5℃, percentages of diseased plants were lower than at 10 to 20℃ (Table 1). In Norin No.61, many plants were diseased, except for 5℃, and the disease appearence was characterized by very low percentage of smutted main culms in contrast to disease development on tillers in almost all diseased plants. In Yuyake-komugi, no plants were diseased. The mode of disease appearence in these varieties as mentioned above, seemed to be attributable to intrinsic resistance to flag smut of the varieties, which is not much influenced by soil temperature. 2. 14 days after the seeds of each variety were inoculated with the spores and sown in the soil regulated at 15℃, some seedlings were picked up from the soil and the distribution of hyphae within their tissues was examined under a microscope. Remaining seedlings were transplanted to sterilized soil in pots, and disease development was observed as the plants became mature. Hyphal penetration was found to occur through epidermal cell wall of coleoptile, and the hyphae advanced in the direction shown in Fig.1. In Yuyake-komugi, the penetration was checked by callus formed at the point of hyphal entry. The callus was characterized by a thickening,both inside ahd outside, of the epidermal cell wall and lustrous yellow coloring. In rare cases, callus was pierced by penetrating hyphae, but the hyphae died within the epidermal cell, presumably due to disorganization of cytoplasm of this cell, and could not penetrate into neighbouring cells. In Norin No.50, most penetrating hyphae could invade epidermal cells of coleoptile without producing callus, but in some cases, callus was noted around the penetrating hyphae on the inside of the epidermal cell wall. Further development of the hyphae was checked. In Norin No.61, the mode of penetration of the fungus was not much different from that in the susceptible variety, although callus formation was rather frequent. 3. Percentage of diseased plants observed at maturity stage was 99 per cent in Norin No.50, 63 per cent in Norin No.61, and O per cent in Yuyake-komugi (Table 2). According to microscopic observations, percentage of seedlings which had coleoptile tissues occupied by the invaded hyphae was 100 per cent in Norin No.50, 50 per cent in Norin No.61, and O per cent in Yuyake-komugi. These facts seemed to indicate that callus formed at the point of penetration would have an important role in the resistance of the host to the fungal attack. On the other hand, symptoms appeared on main culms in 96 per cent of the tested plants in Norin No.50, 9 per cent in Norin No.61, and O per cent in Yuyake-komugi. Percentage of plants in which the hyphae reached the epicotyle tissues or near them eristematic regions, developing through the coleoptile tissues was 90 per cent, 25 per cent, and O per cent, in respective varieties. These facts showed that the hypha of flag smut fungus could reach the growing points of main culms when hyphal development in the coleoptile tissues was rapid, and that the hyphal development in the tissues was more rapid in Norin No.50 than in Norin No.61.
日本植物病理学会の論文
1964-05-30

抵抗性の異なる品種におけるコムギから黒穂病菌感染の差異

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