水稻の稻熱病に對する罹病性とその主要

化學成分との關係(第3報)

抄録

In this paper, the results of inoculation experiments with blast fungus on the rice plant and the chemical analysis of the plants are described; the relation between the susceptibility of the plant to blast disease and its chemical components is also discussed. Throughout all the experiments, a rice variety "Eiko" was used.
Inoculatin experiments using water-cultured rice plants, grown with various amounts of nitrogen, indicate that the plants supplied with the larger amounts of nitrogen are apt to be the more severely attacked by the blast fungus, producing more numerous and larger lesions. And it is found by chemical analysis that the plants given the more nitrogen contain the more α-amino nitrogen; this fact is especially conspicuous in the plants supplied four-fold and five-fold amounts of standard nitrogen. Potted rice-plants were inoculated with the blast fungus before and after the top dressing, and, parallel to the experiment, the plants remained uninoculated were chemically analyzed. It is found that the plants come gradually to be more severely attacked by the fungus within two days after the top dressing than they were before, and the plants treated with top dressing become gradually more rich in α-amino nitrogen and amide nitrogen after two days following the top dressing.
The above described experiments seem to show that the amount of soluble organic nitrogenous components such as α-amino acid and amide, is connected with the susceptibility of rice-plant to blast disease.
According to the present author's previous report the seedlings raised in hot bed nursery cotain much more soluble protein nitrogen, α-amino nitrogen and basic nitrogen in comparison with those raised in the ordinary nursery; the former are apt to be more severly attacked by blast fungus.
Both at the ear-formation stage and the boot stage the leaves of rice plant contain more soluble organic nitrogen than the leaves at the other growing stages while they are apt to be seriously attacked by the fungus at the stages mentioned above. No relation between the susceptibility of rice plant to blast disease and the sugar content of rice plant is found.
Using these experimental results the author calculated the correlation coefficient between the size of lesions and the amount of various nitrogenous components. The correlation between the size of the lesions and soluble organic nitrogen, particulary the basic nitrogen and α-amino nitrogen, is perfect. Increase of the above-mentioned nitrogenous components in the rice plant, therefore, may be favorable for the growth of the fungus in its host plant and make such plants more susceptible to the blast disease.