The blast resistoance of the numerous rice varieties amounting to almost four hundreds which are native to the different latitudinal regions in Asia has been compared by means of the artificial inoculation in the glass house as well as by considering the data obtained from the natural infection in the field. So far as the leaf-blast resistance is concerned, the variety-groups which are separated according to the habitats can be classified into following three categories. (1) The variety-groups, all of which show infection-type A. (vid. fig. 1). Variety-groups of Japanese lowland, “Hôrai” (Japanese lowland type bred in Formosa), and North China are involved herein. (2) The variety-groups which reveal a striking intervarietal variation as regards the infection-type (i. e. from A to F). Variety-groups of Japanese upland, Formosan upland (in the mountain regions), middle & South China, and Europe & America are involved. (3) The variety-groups which exhibit a moderate intervarietal variation as regards the infection type (i. e. from B to F). Variety-groups of Eormosan endemic (except upland), Philippines, Celebes, Great & Lesser Sundas, French Indo-China, Siam, Burma and India are involved. Considering the above-named data, it seems that the Japanese lowland group is consisted of the closely related varieties which might have been originated from certain allied genes, but it is of almost no doubt that the variety-groups other than the Japanese lowland are mixed with the varieties different in their genetic constitution. So far as the percentage of ear-and node-blast infection is concerned, such a marked difference as evidenced in the leaf-blast resistance was not found between the temperate and tropical group. In general, however, the percentage of neck blast infection was lower in many of the variety-groups native to the tropical region than in those to the temperate, though that of the node-blast infection was often opposed to the above.
A pot experiment was made to determine the effect of phosphate application upon the infection of rice seedlings by blast fungus, Piricularia oryzae. The phosphate deficiency in the soil made the rice plant susceptible to rice-blast. But, the excess of phosphate over the necessary quantity for growth gave no protective effect from riceblast. So that the application of phosphatic fertilizer in the soil is effective to the protection from rice-blast in the phosphate deficient soil. but not effective in the phosphate abundant soil, The influence of phosphate deficiency of rice plant on the infection of rice-blast was intensified with the large supplies of nitrogen. As it is known that the phosphate unavailable under low temperature becomes available for plants with the increase of temperature in the field especially in the paddy field, the appication of phosphatic fertilizer acts effectively for the control of the said disease, under the lower temperature rather than under the higher temperature.
The present experiment has been carried out to determine the effect of dried-mycelium powder of a Cephalosporium sp., an antibiotic-substance producing fungus, upon the development of leaf blast of rice plant. The roots of rice seedlings were immersed for 48 hours in the mycelial-powder suspensions of 0.1, 0.05, 0.025, and 0.0125 percent respectively. The seedlings, treated with suspensions of all concentrations except 0.025 percent, were promoted in growth and turned deeper green in color than the check plants. Thee leaf spots on the seedlings treated with 0.10.05 percent suspensions, decreased in number nearly to a half of those of the controls. The reduction in degree of infection was apparently in proportion to the dosis of the dried-mycelium powder.
The present paper deals with the criticism on the diagnostic value of the “Jodine method” and the “Phenol method” for virus-infected potato tubers. The Jodine method formerly proposed by WARTENBERG and KLINKOWSKI was slightly modified by the writer. A test tube contains 0.5 cc. of potato juice, in which 0.5 cc. of diluted pasty starch solution (1.5 g. of starch in 100 cc. of dist. water) and 15 cc. of Jodine solution (2 g. of Jodine in 100 cc. of 30%ethyl alcohol) are added. These test tube series were kept under a room temperature (about 30°C.). The diseased tuber juice fades more quickly (within 50 minutes) than that of the healthy (more than 3 hours). The diagnostic value was about 70% when 74 tubers of Benimaru variety were tested immediately after harvest, and remarkably lower when the tubers sprouted. Furthermore the Jodine method is very dificult to determine the adequate dose of the juice and the reagents. In the case of the Phenol method, a series of test tubes which contain 1 cc. of potato juice and 0.2 cc. of 0.1% phenolic solution was kept under the room temperature. In 5 hours the healthy becomes dark brown in color, while the diseased whitish yellow. The slice of tuber dripped with Phenol shows the similar result. The diagnostic value of this method was yet very low.
1. Using the WARBURG'S respiration manometer, the respiration of the tissues of tobacco plants infected by ordinary mosaic virus was compared with that of the healthy plants. 2. In the diseased leaf tissues, the amounts of oxygen consumption and carbon dioxide production are greater than the healthy one, but the repiratory quotient shows the similar value of about 0.94. Anaerobic respiration is also stronger in the diseased leaves. The increase of respiration in the diseased leaves is markedly accelerated in older infected leaves. 3. In the root tissues, the consumed oxygen is the same degree in the diseased and healthy plants. The carbon dioxide production both in the aerobic and anaerodic conditions is very low in the mosaic plants. It is considored that the low value of respiratory quotient is due to the imcomplete oxidation in the process of the aerobic respiration in diseased plants. 4. The expressed juice of the mosaic plants showed no detectable gas exchange. 5. The expressed juice of diseased leaves does not affect the respiratory rate pollen of Lilium longiflorum.