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.
STUDIES ON THE SHEATH ROT DISEASE AND ITS RELATION TO THE STERILITY OF RICE PLANTS