When Fusarium oxysporum f. niveum Snyder et Hansen was shake-cultured for 3∼4 days at 28°C on 5% glucose-potato extract, a pigment was enormouly formed in the mycelium. The pigment changes color from red to blue when the reaction of the medium changed from acid to alkali. The pigment was isolated from the HCl (3:1)-treated mycelium by extraction with chloroform. The purified pigment was red, platelet or lens-shaped, m. p. 310∼1°C. (decomp.), empirical formula being C20H16O8. It was proposed from the results of acetylation, methylation, infrared absorption spectra, and other examinations, that it is probably a quinoid pigment having two hydroxy and two methoxy radicals, and it may be identified with lycopersin, a pigment of F. lycopersici, isolated and named by Kreitman et al. It seems that this pigment is universally present in Fusaria belonging to the species oxysporum.
Using Triticum spelta, T. timopheevi, T. vulgare, and Oryza sativa, seedlings at 2 leaves were irradiated by X-rays or by gamma-rays, at 10, 30, 50 and 70kr. The seedlings were inoculated 1 and 7 days after irradiation by spraying with an aqueous uredospore suspension (Puccinia triticina 21 B), and the effects of radiation on the susceptibility to the leaf rust were observed. In seedlings of the same age, the first and second leaves were sampled, and the amounts of amino-nitrogen and reducing sugar were measured. Effects of irradiation on leaf characters, namely stomata size, internal structure, viability, and sporulation of the fungus on the irradiated leaves were examined. Rust susceptibility of the irradiated plants (T. spelta and T. vulgare) was increased, as compared with the non-irradiated plants. In T. timopheevi which was inoculated 7 days after irradiation, the third leaf was susceptible, while the first and second leaves of the same plants were mostly resistant. The irradiated rice plants remained immune. In T. timopheevi, the amount of amino-nitrogen was higher in the seedlings 1 day after irradiation, as compared with that of the non-irradiated seedlings, while it was lower 7 days after irradiation. The amount of reducing sugar increased seedlings 1 and 7 days after irradiation, in comparison with the non-irradiated seedlings. Stomata size and internal structure of the irradiated plants (T. spelta and T. vulgare) did not change noticeably, as compared with the non-irradiated plants. Effects of irradiation on the viability of leaves were tested. When the growing point suffered radiation damages, the already developed leaves longer the remained fresh than those of the non-irradiated plants. The uredosori of the leaf rust produced on irradiated T. vulgare were larger than on normal plants. Relationships between rust susceptibility an irradiation await further experiments.
In order to examine the susceptibility of the Oryzae to the blast fungus 92 strains of 20 species belonging to the genus Oryza, 3 interspecific Oryza hybrids, 2 strains of Zizania latifolia, and a strain of Chikusichloa aquatica were tested in a greenhouse with 2 isolates of Piricularia oryzae, namely P-2 and 54-04. The plants were grown in Wagner's pots, being fertilized with ammonium sulphate, calcium superphosphate and potassium sulphate. They were inoculated by spraying spore suspensions on the third and fourth leaves, or by injecting the suspensions with a hypodermic syringe into the fifth to seventh still folded leaves. The degree of susceptibility was determined by the degree of lesion formation on the leaves. The experimental results, in general, showed that the injection method was more efficient than the spraying method, and as to the pathogenicity, the isolate P-2 was more virulent than the isolate 54-04. O. sativa f. spontanea, O. perennis, O. barthii, O. stapfii, and O. breviligulata, which are closely related to the cultivated rice, exhibited either resistance or susceptibility to both these isolates of the blast fungus, according to strains within a single species. Other plant species which are distantly related to the cultivated rice, generally exhibited susceptibility or a moderate resistance. Zizania latifolia was highly resistant, while Chikusichloa aquatica showed susceptibility. Any relationships between the susceptibility and locality, chromosome number, or genome formula were not obvious.
Studies on physiologic specialization of stem rust of wheat (Puccinia graminis tritici (Pers.) Erikss. et Henn.) were carried out with 56 uredosorial samples collected from various parts of Japan during 1957 to 1960. These isolates revealed the presence of three races in Japan; namely physiologic race 56 collected twice in Nagano Pref. in 1957, physiologic race 21 most frequently and widely distributed all over the country, and race closely related to 11, being collected twice in Nagano Pref. in 1959, and once in Niigata Pref. in 1960. The seedling reactions of many wheat varieties and related plants were examined to each race. Most of them were susceptible to all three races. Triticum timopheevi and its derivatives were immune or highly resistant to all three races. It needs introducing of wild wheat genes for breeding stem rust resistant varieties. It draws our attention that the race compositions of wheat stem rust in Japan is very simple in contrast to wheat leaf rust. This may be attributed, at least as a part, to scarceness of passage through alternate hosts, owing to absence of susceptible barberries, and poor germinability of teliospores.
The dwarf disease of mulberry tree had been considered to be a physiological trouble induced by severe pruning and plucking the leaves in the summer until 1931, when Akiya demonstrated that the disease was graft-transmissible and Ikata and Matsumoto succeeded in transmitting it by means of a leafhopper, Hishimonus discigutus (Walker), suggesting that this disease may be caused by a virus. The present author tried a series of grafting experiments to transmit this disease during the period from 1957 to 1960. The disease could not be transmitted-no disease symptom was produced-by stem-grafting when the diseased scions collected in winter were grafted on healthy stocks in April. Moreover it was found that the diseased scions became recovered producing new healthy shoots. But by crown-grafting in which healthy scions were grafted on the diseased stocks, the disease was readily transmitted to the healthy scions. Most, plant virus diseases are transmitted to the healthy host plants by budding or stem-grafting and it is rather peculiar that the mulberry dwarf disease is not transmitted by stem-grafting but by crown-grafting.