In reclaimed paddy-fields in Tokushima Prefecture converted from upland fields where wheat, barley or mulberry had been cultivated, the sterility in rice-plants is frequently found for 1-3 years after the conversion, but not thereafter. The injury of this kind is seldom found in the converted fields where water is not retained for a long time and, therefore, the frequent irrigation is necessary, but it is apt to appear in the water retainable fields. Especially it seems that green manure or immature organic manure accelerates the outbreak of this injury. Concerning the action of bacteria the author campared the soil of converted paddy-fields with that of mature paddy-fields where rice-plants are cropped every year. According to his investigation, in the soil of mature paddy-fields which have long been under cultivation of rice-plants, the growth of Microspira desulfuricans (Beij.) van Delden and Thiobac. denitrificans Beij. is very vigorous, while in the soil of the fields which are designed for conversion or cultivated for one year after conversion, the distribution of these bacteria is scarcely found. However, in the soil of 2-3-year-old converted paddy-fields they are observed to grow gradually, and especially in the soil of 3-year-old converted paddy-fields the bacterial growth is vigorous as well as in the mature paddy-field. In converted paddy-fields the production of organic acids may be remarkable, especially if green manure or immature compost is added, in comparion with mature paddy-fields.
筆者らはさきに東大・農化抗生物質研究班と協同で約1万株の土壌微生物のなかから抗稲熱病性抗生物質生産菌12株を得,このなかからBlasticidin, Blastmycinの2つの抗生物質及びAntimycinA生産菌株A-720を発見した。別に原田らは抗黴性抗生物質としてAntipiriculinを発表したが,これはAntimycin Aに一致することが判明した。筆者らはAntimycin A, Blasticidin及びBlastmycinの稲熱病菌に対する作用,薬剤散布後の葉面における安定性,葉面散布による葉稲熱病防除効果等について調べたので,その結果を報告する。
Phytoalexin (PA for short) has been defined by Müller (1954) as antibiotics which are the result of an interaction between the host and the parasite, and which inhibit the growth of microorganism pathogenic to plants. In the present paper the results are dealt, of a study on the rate of production of PA, as affected by host plant conditions, and activities of PA, using soybean (Gylcine max Mer.) and Fusarium sp. which causes pod blight. Drops of spore suspension of Fusarium were mounted on the inner surface of the seed rooms of the pods at different ages, and after centrifuging, the supernatant was tested for inhibitory action on the germination of fresh spores of Fusarium. It was found that the PA diffused distinctly into the drops placed on the young, unmatured pods, while hardly or not in the drops on the mature pods. The PA productivity of the host tissue was determined by changing daily the drops placed on given points of young pods with new spore suspension, and by measuring the inhibitory action of the diffusates on each day. It was shown that the production of PA decreased remarkably on the second day, and sank nearly to zero on the fourth day. PA in the diffusate from the pods lost most of its inhibitory activity, when heated at 100°C for 5 minutes or diluted to 1:8.
This paper reports some experiments on the nature of Phytoalexin (PA) produced as a result of the host-parasite interaction between pea, Pisum sativum L., and Ascochyta pisi Lib. Drops of spore suspension of A. pisi were placed on the seed rooms of pea pods and kept in moist chamber at 22°C. for 24 hours. These drops were then collected and centrifuged for 30 minutes at the rate of 3500 r.p.m. The supernatant, PA-solution, was subjected to treatments shown below, and then placed on the slide glass in moist chamber with the addition of the spore suspension of A. pisi for the purpose of the germination test. The procedures were carried out under aseptic condition, as possible. The experiments and the results were as follows: 1) PA-solution was irradiated by ultraviolet-ray for various minutes at a distance of 45cm from the energy source. The source of ultraviolet-ray was a Tôshiba lamp for sterilization (model 1510 B, lamp GL-15×1). This lamp charged the rays between 1850 and 5780Å, but the greater parts were collected at 2537Å. The results showed that the activity of PA-solution was nearly lost by the exposure for 45-60 minutes (Table 1 and Fig. 1). 2) When PA-solution with active carbon was added at a rate of 10gr. per liter and shaken for 5 minutes, the activity of the solution was lost (Table 2). 3) When PA-solution was dried in the air for 24 hours at 22°C., the inactivation of the solution was resulted (Table 3). 4) Both pH and specific electric conductivity of PA-solution were measured, using the glass electrodes pH-meter and Wheatstone bridge respectively. The pH value was 5.7-5.8 and specific electric conductivity calculated from the electric resistance, was 164×10-6 mho. (Table 4).
1) Various plant species, as many as 260 species in 74 families, were tested for susceptibility to the ordinary strain of the cucumber mosaic virus. Inoculations were made by the juice-rubbing method using carborundum powder. Plants in 117 species belonging to 39 families were infected by the virus. Local lesions developed on the inoculated leaves of plants in 20 species belonging to 9 families; systemic infection did not occur in these plants. 2) Forty-five species and varieties of plants, previously not reported as hosts of the cucumber mosaic virus, were found to be infected in this experiment. These are Chrysanthemum coronarium, Cucumis melo var. Conomon, C. melo var. Makuwa, Cucurbita moschata, Rubia cordifolia, Sesamum indicum, Veronica arvensis, Verbascum Thapsus, Linaria bipartita, Torenia crustacea, Nicotiana longiflora, Datura Tatula, Tubocapsicum anomalum, Solanum sisymbrifolium, Mentha arvensis, Cynoglossum amabile, Cuscuta japonica, C. sojagena, Ipomoea Nil, Cryptotaenia canadensis, Daphne odora, Viola mandshurica, Abelmoschus esculentus, Papaver orientale, P. Rhoeas, Argemone mexicana, Stellaria media, Silene Armeria, Gypsophyla elegans, Dianthus chinensis, D. Caryophyllus, D. superbus, Lychnis coronaria, Cerastium vulgatum, Portulaca oleracea, Mesembryanthemum spectabile, Phytolacca esculenta, Gomphrena globosa, Amaranthus tricolor, Chenopodium stenophyllum, C. Anthelminticum, Zingiber mioga, Musa basjoo, Lilium tigrinum and Colocasia Antiquorum. Among these, there are several plant species in which successful isolation of the virus from naturally occurring mosaic plants were reported in Europe and America, although no inoculation trials to the healthy plants were reported. 3) Negative results were obtained with Centaurea Cyanus, Ambrosia artemisiaefolia, Valeriana officinalis, Daucus Carota, Tropaeolum majus, Pelar gonium inquinans, Tulipa Gesneriana, Hyacinthus orientalis, Lilium cepa, Secale cereale and Triticum vulgare. These species were reported to be susceptible by previous workers. On the other hand, Papaver orientale which was listed as non-host in the U.S.A was infected in the present experiment. 4) It is considered that in the cucumber mosaic virus, are involved many strains which differ in their host range as well as in symptom expression on certain host plants. Consideration of the virus host range with special reference to plant phylogeny will be given in a later paper.