稻葉鞘腐敗病之研究及其對不稔症發生關係

Abstract

自典型病斑所得菌株之最適生長溫度為32℃，自不稔病株葉鞘褐孿部位所得菌株之最適溫度為30℃，故葉鞘腐敗病菌之生長最適溫度在30~32℃。但稻葉鞘腐敗病病勢進展之最適溫度為26~28℃，比病原菌生長之最適溫度稍低。 不稔病區之水稻在稻形成幼穗後不久，自該幼穗就可分離到葉鞘腐敗病菌，一直到成熟期皆可獲得病原菌，一般穀粒的穀殼上潛伏病菌之頻度比糙米多。 水稻受傷痍時其惑染率可達88%以上，而無傷痍稻較難被惑染。稻細蟎體，蛻皮或卵上附著甚多的病原菌，因此稻受稻細蟎加害時，亦容易引起病害之發生。 放飼稻細蟎後接種病原菌對稻不稔之影響，比單獨接種病原菌或放飼稻細蟎區為大。 160個品種在自然環境下，被惑染葉鞘腐敗病之程度，日本型稻群比印度型稻群內之感病品種較多。 This paper deals with the rice sheath rot pathogenic fun gus, Sarocladium oryzae, influence, of. sheath rot disease and tarsonemid mite on the sterility of rice plants. The experimental results showed that S. oryzae had a wide range of temperature for growth. Tests of 3 S. oryzae isolates (SO-1 and SO-2 were isolated from brown tissues of rice sheath, SO-3 was from typical lesion of sheath rot) indicated that the favorable temperature for growth of SO-1 and SO-2 was at 30℃ and for SO-3 was 32℃. Therefore, the optimum temperatures for growth of S. oryzae were from 30 to 32℃. Favorable temperatures for disease development were lower than that for the growth of S. oryzae. The optimum temperatures for disease development were around 26-28℃. S. oryzae could be isolated from young-head shortly after young-head formation and until maturity. It was more easy to isolate S. oryzae from grain shell than from brown rice. The percentage of infection could be reached 88% when rice plants were injuried. However, it was difficult to establish the infection without wounding. A lot of conidia were adhesive on the bodies of tarsonemid mite. Pure culture of S. oryzae could be easily obtained from bodies, ecdyse or eggs of tarsonemid mite. Rice plants inoculated with mite and S. oryzae were more severe than those plants inoculated with S. oryzae or mite alone. Among 160 rice varieties under natural conditions, japonica type werer more susceptible than indica type to sheath rot disease.