1. Die Fleckengrößeverteilung bei der Brennfleckenkrankheit von Reispflanzen ist nicht normal, sondern eine spezifische Verteilung, die sich nach links stark verbiegt, wie bei der Helminthosporiose. 2. Die Flecke selbst an anfälligen Geweben sind meist punktiert klein, und nur wenige von ihnen groß und angreifend, während alle Flecke an resistenten Geweben punktiert klein sind. 3. Bei Kultur des Pilzes auf gewöhnlichen Nährboden wachsen die Hyphe des Erregers unbegrenzt, und ihre Koloniengröße liefern eine normale Verteilung; dagegen an den lebenden Blättern ist die Wachstumskurve der Flecke asymptotisch. 4. Unter diesen Resultaten disktiert der Autor darüber, daß man die Fleckengrößeverteilung als eine Verteilung von Wachstumsdauer eindringender Pilze erkennen und den zeitlichen Ablauf der Widerstandsfähigkeit des Wirtsgewebes beschreiben kann.
The causal virus of mosaic disease of asparagus-bean and cowpea in Japan was investigated and the following results were obtained: 1) This virus was easily transmissible by pressed juice and also by aphids, Myzus persicae and Aphis medicaginis. Transmission tests with A. gossypii were unsuccessful. Both acquisition and inoculation feeding thresholds of Myzus persicae were between 10 and 15 seconds. 2) Seed transmission rate of this virus was 0.24 per cent in the case of Vigna sesquipedalis, when 2914 seedlings were used for the test. 3) Among 38 species of Leguminosae and 8 species of non-leguminous plants tested, the susceptible plants were shown to be as follows: Astragalus sinicus, Canavalia ensiformis, Phaseolus angularis, P. lunatus, Vigna sesquipedalis, and V. sinensis. All these species produced systemic mottling. Cassia tora formed only black local lesions. Phaseolus vulgaris formed faint chlorotic local lesions, or caused symptomless local infection, but some varieties were immune from the disease. Aeschynomene indica and Canavalia gladiata were symptomless carriers. Vicia faba formed reddish-brown local lesions, but was not systemically infected. 4) Thermal inactivation point of this virus lay between 55 and 60°C. Longevity in vitro was found to be between 12 and 24 hours. Dilution-end point was between 1: 1, 000 and 1: 2, 500. 5) Strains isolated from seed-borne diseased asparagus-bean plants found to be almost the same in respect to host range, physical properties, and transmission.
1. From cabbage and rape plants showing mosaic, collected in the vicinity of Tokyo during April 1960, several virus isolates were obtained; also from radish plants showing stunting. All of these virus isolates were tested, and found to be similar. The experiments reported here were made using a cabbage virus isolate. 2. Host range: (susceptible: showing vein-clearing, vein-banding, mosaic, and/or necrotic-spots): Brassica rapa var. glabra, B. pekinensis (two subvarieties), B. oleracea var. capitata, B. oleracea var. botrytis, and Raphanus sativus var. acanthiformis. (Not susceptible): N. tabacum, N. glutinosa, Vigna sesquipedalis, Vicia faba, Cucumis sativus, Chrysanthemum coronarium, and Chenopodium album. At high temperatures, symptoms on cabbage and cauliflower (vein-clearing, vein-banding, and/or warty enations) rapidly became masked. Symptoms on turnip and radish (vein-clearing, veinbanding and/or stunting), however, were conspicuous and persistent, without regard to temperature. 3. Properties: Dilution end-point in extracted leaf juice was 1: 20, 000∼100, 000. Thermal inactivation point was between 75∼80°C in 10 minutes treatment. Longevity of the virus in crude juice was between 25∼35 days at 22°C. 4. Aphid transmission: The virus was readily transmitted by aphids, Myzus persicae and Brevicoryne brassicae. The mode of transmission was of non-persistent type. 5. Purification: Attempts were made to obtain a purified virus preparation, using diseased turnip leaves. The final procedure adopted was as follows; treatment at 64∼65°C for 10min.→ shaking with chloroform→repeated salting-out by ammonium sulfate, and cycles of differential centrifuging. The final product in solution was almost colorless, and it showed a maximum absorption at 260mμ, and a high infectivity in inoculation tests (infective at a dilution of 104 of the final preparation in solution). 6. Electron microscopy: Examination of the purified virus preparation revealed the presence of uniformly-sized spherical particles of about 10∼13mμ in diameter. The preparation was found to be almost free from other particulate matter. The shape of the particles was thought to be polyhedral rather than spherical, judged from their mode of aggregation. 7. Serological tests: Precipitation reaction between this virus and the antisera against radish P virus, radish R virus, or cucumber mosaic virus, turned out to be negative. 8. It is considered that this virus ought to be identified as the cauliflower mosaic virus described by Tompkins (1937), although the size of the virus particle was found to be different from that reported by Day et al. for the Australian cauliflower mosaic virus.
Xanthomonas oryzae bacteriophage collected from various places of Japan could be classified into 4 strains, OP1, OP1h, OP1h2 and OP2 on the basis of their host range. It appeared that OP1 and OP1h2 were the ones more extensively distributed than the other phage strains in Japan. On the basis of susceptibility to these phage strains, 82 isolates of X. oryzae collected from various places of Japan were classified into 5 strains as follows; A strain: Susceptible to OP1, OP1h2 and OP2 but not to OP1h B strain: Susceptible to OP1h, OP1h2 and OP2 but not to OP1 C strain: Resistant to all of these phages D strain: Susceptible to OP1h2 and OP2 but not to OP1 and OP1h E strain: Susceptible to OP2 but not to OP1, OP1h and OP1h2 Of these bacterial strains, A strain was the one most widely and commonly distributed in Japan, followed by B, D, C, and E strains in decending order. There was found no specific rule in the distribution pattern of these strains.