Studies on the Fungi Isolated from Root of Rice Plants Cultivated under Different Environments and Its Relation to the Development of Rice Root

由稻根共分離18屬真菌，分別為Aspergillus, Botryoderma, Chaetophoma, Ciadosporium, Curvularia, Fusat-ium, Homococus, Paeciiomyces, Papularia, Penicillium, Pestalotia, Pullularia, Rhionotrichum, Rhizoctonia, Scytalidium, Stysanus, Trichoderma及Verticillium，抽穗期根棲真菌之族羣密度比乳熟期為高。利用人工接種，上述真菌均能侵入稻根。有些菌株更會造成稻根產生褐變現象。 Eighteen genera of fungi were isolated from rice roots. They were Aspergillus, Botryoderma, Chaetophonza, Cladosporiunz, Curvularia, Fusariurn, Homococu, Paecilom yces, Papularia, Penicilliurn, Pestalotia, Pullularia, Rhinotrichum, Rhizoctonia, Scytal dium, Stysanus, Trichoderma and Verticillium. The population of rice root-inhabitant fungi during the heading period of rice was higher than which on the milky stage. All fungi could be able to infect the rice root by artifical inoculation. Some isolates made the rice root as a result of discoloration

(29(1):27-33)Pathogenicity of different anastomosis groups of Rhizoctonia solani Kűhn to potatoes

馬鈴薯「五豐」及「克難」兩品種對Rhizoctonia solani 引起之黑痣病均屬感病性。生育後期（80 ~95 天）田間發病率「五豐」為31.2 士3.2 % ，收穫前「五豐」為52.7 士7 %，「克難」為16.4 士3.7 %。R. solani 各菌絲融合群（TRAG）侵害馬鈴薯之比率為：TRAG 1佔9.3 % , 主要由莖部侵入後蔓延至莖基部及塊莖上；TRAG 2 佔11.1 % ，本群病原性較弱，主要危害莖部；TRAG 3 及TRAG 4 各佔39.9 與38.9 % ，均可分另別由莖、莖基部及種薯侵入為害。 Potato cultivars, such as Wu-feng and Ko-nan, were susceptible to black scurf caused by Rhizoctonia solani Kűhn. A survey carried out in the 1977/1978 period indicated that there were 31.2 ± 3.2% and 52.7±7% of disease for the variety Wu-feng at the late growth period and the time prior to harvest, respectively. While there were 16. 4±3.7% of disease for the variety Ko-nan at the time prior to harvest. Of those diseased potatoes, about 9.3% were caused by isolates of anastomosis group 1 (TRAG 1) which infected stems and eventually extended to stem bases and tubers, about 11.1% were incited by isolates of anastomosis group 2 ( TRAG 2) which showed weeker pathogenicity and were only able to infect stems, and about 39.8 and 38.9% were incited by isolates of anastomosis groups 3 and 4 (TRAG 3 and 4), respectively. Both TRAG 3 and TRAG 4 could infect stems, stem bases and tubers