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.
In the present paper are given the results of histopathological observations on the infection of peach by Gloeosporium laeticolor. As previouly reported (4), the anthracnose fungus first attacks the trichomes of young fruits. The infection hyphae penetrate into the trichome cells and the mycelium passes into the epidermal cells of young fruits (Fig 2). The mycelium grows very rapidly in the young fruit tissue and usually runs out from the dead tissue (Fig 3). The fungus then invades into the twig through the peduncle without causing fruit-drop. Isolations from the serial cut-pieces of the affected twigs demonstrated that in late spring the coloniation by the fungus was restricted to the vicinity of the point of attachment of the diseased young fruit, but the mycelium spread gradually until December to permeate through the infected twig. The affected twig, however, remained alive as late as the next April (Fig 6). The fungus can penetrate a young shoot besides trichomes of a fruit. Under natural conditions, however, the shoot grow too old to be infected when the conidia are disseminated. Therefore, it is concluded that the young fruit is practically the sole entry port of the peach anthracnose fungus.
TUMANOV, in his study on the snow killing of wheat plants, said that the wheat plant under snowcovering came to utilize protein as a respiration material after they had consumed the reserved sugars, and the subsequent breakdown of protein by promoted proteolysis caused the weakening of resistance of wheat plant to the attacks of snow blight fungi and might result severe damages. However, the present writer's experiments showed that, in the older leaves a remarkable proteolysis took place soon after the plants were covered with snow, despite a fairly large amount of carbodydrates remained unconsumed, whereas, in the younger leaves, such consumption of protein was not actually observed even far later in the season. In reality, the infection of older leaves of wheat plants by Typhula Itoana and T. ishikariensis takes place at the beginning of snow covering. T. ishikariensis developed first in the older leaves attacks readily the younger ones and causes frequently the entire decaying of the whole plant. T. Itoana, on the contrary, can hardly attack the younger leave, wherefore, this fungus scarcely causes the entire decaying of the wheat plant under ordinary condition. The wheat plant affected previously by T. Itoana frequently escape from the attack of T. ishikariensis on account of the antagonistic relationship between two pathogens, and it means that the winter wheat can escape the severe damage caused by T. ishikariensis owing to the previous infection by mild-virulent T. Itoana. From these results, it is concluded that the leaf age, the resistance of younger leaves of wheat plants to the pathogens, and the relative frequency of occurrence of T. Itoana and T. ishikariensis are important factors affecting the winter-killing of wheat plants under snow covering.
Inoculation experiment on seedlings and pods of beans were carried out to have clear knowledge about the varietal resistance to the anthracnose caused by Colletotrichum Lindemuthianum BRIOSI et CAVARA, using 44 varieties of native and foreign origins. Four strains of the causal fungus isolated from diseased pods of two varieties, Kintoki and Concord, and from affected seeds of Burma were used. The results of the inoculation experiments on seedlings showed that a number of varieties, namely, Kintoki, Tenashi-naga-uzura, Chunagauzura, Concord, etc., are susceptible and others such as Tenashi-chunaga-uzura, Kikuchi-naga-uzura, Tsunetomi-naga-uzura, Satisfaction, O-tebo, etc., are resistant. In spite of the general opinion that the pole bean varieties are resistant and the bush bean varieties are susceptible, the results of the present experiments showed that some of the pole bean varieties (Concord, Uzura) are susceptible and certain bush bean varieties (Tenashi-chunaga-uzura, Satisfaction, Beni-kintoki, etc.) are resistant. The results of the inoculation experiments on pods of six varieties whose resistances in the seedling's stage have already been graded, showed that there existed a parallelism between the seedling's resistance and that of pods.
Erysiphe cichoracearum DC., Sphaerotheca fuliginea (SCHFECT.) POLL., and Sph. humuli (DC.) BURR. are reported as the powdery mildew fungi attacking cucumber and other members of cultivated cucurbitaceous plants. While in Fukuoka so far observed, Sph. fuliginea is the only cause of the mildew of the cucurbitaceous plants. The occurrence of perithecial formation of Sph. fuliginea on cucurbitaceous hosts is not uncommon in Fukuoka late in the fall, though it is said difficult to find the perithecia in other districts of Japan. The mildew fungi (E. cichoracearum and others) obtained from Nicotiana tabacum, Artemisia vulgaris, Sesamum indicum, and Bidens bipinnata are not infectious to cucumber, while the fungus from Arctium lappa (Sph. fuliginea) is pathogenic to cucumber. Sph. fuliginea from cucumber is infectious to Arctium lappa and Phaseolus radiatus, but is not infectious to Solanum melongena, Chrysanthemum coronarium, Helianthus tuberosum, Hel. annuus, and Nicotiana tabacum. The difference of resistance due to the difference of ages of the leaves of cucumber against the infection by Sph. fuliginea has been observed. Young leaves which had past 0 to 3 days. before the inoculation, in this experiment, were not affected when examined 5 days after inoculation, and the most susceptible leaves were those which had past 16 to 23 days before the inoculation.
In the present paper the writer intends to report on the results of the author's pathological and physiological researches on culture filtrates of the causal fungus of black spot disease of Japanese pears, Alternaria Kikuchiana TANAKA. 1) The results of biological experiments on toxic action of culture filtrates of the fungus to host plant were described. 2) The pathogenicity of culture filtrates of 25 species and 8 strains of phytopathogenic fungi belon-ging to genera, Alternaria, Fusarium, Colletotrichum, Macrosporium and Venturia was tested. It was decidedly considered that the characteristic symptom of the disease appears only by Alternaria Kikuchiana. 3) Effect of deficiency of some elements in synthetic nutrient solutions on the pathogenicity of Alternaria Kikuchiana and toxicity of culture filtrates, was studied. From the results, it seems that there is an exact relation between the occurreence of the disease and culture filtrates and also the protoplasmic speciality of host plant. The protoplasmic speciality of host plant is remarkably sensitive to culture filtrates of the causal fungus, accordingly, in the present paper the term, HYPERSENSITIVE DISEASE OF PLANTS is newly suggested by the writer. (Laboratory of Phytopathology, Faculty of Agriculture, Tottori University)
In nature Sclerotium Rolfsii attacks the hosts usually at their foot. In a case was observed by the author a Hibiscus plant attacked at about a meter above the ground. By what means the pathogene reached at that height is still unknown. It may be possible that the infection has been caused by basidiospores transported by flow of air. It is therefore interesting to know the relation of germination of basidiospores.
The writers found the ascigerous stage of the cucumber anthracnose fungus, Colletotrichum lagenarium (PASS.) ELLIS et HALSTED, in a potato agar culture in March 1949. Morphological examinations proved the fungus to be included in the genus. Glomerella. The amount of production of ascospore was scarcely effected by temperature, but the rate of ascosporic production was delayed under higher temperature (25-30°C) than under lower temperature (20-15°C). The fungus produced ascospores more copiously and rapidly in potato-decoction and potato-decoction-agar cultures, compared with cultures on other kinds of media. The fungus differs in important respects from previously described species of Glomerella, especially from the bean anthracnose fungus, Glomerella Lindemuthianum (SACC. et MAG.) SHEAR and is here designated a new species. Glomerella lagenaria (PASS.) WATANABE et TAMURA, nov. sp. Perithecia spherical, subspherical or pyriform, membraneous, immersed in a stroma, dark-brown, 112-256μ in diameter; asci sessile, clavate or cylindrical, hyaline, 47.5-77.5μ in length and 7.5-11.25μ in width; ascospores 8, hyaline, oblong, slightly curved or straight, elliptical or fusoid, 1-celled, 12.5-27.5μ in length and 3.75-6.25μ in width; paraphyses none. Conidial stage: Colletotrichum lagenarium (PASS.) ELLIS et HALSTED in Bull. Torrey Bot. Club, Vol. 20, pp.109-112, 1893.
The rice infected by white tip nematodes was disinfected with simplified hot-water treatment, soaking for ten hours in bath water, the temperature of which was left as it dropped; viz. 44.7-46.1°C at the beginning and 20.7-31.6° Cat the end. Good control, occasionally perfect control was obtained by this treatment. The treat ment had practically no injurious effect on the germination of rice seed. But, it is a matter of concern that the effectiveness of this method may not be constant, as the temperature of bath water is apt to fluctuate too much, influenced by various conditions.