棉籽携带棉铃疫菌及该菌的致死温时

STUDIES ON COTTON SEED-BORN PATHOGEN OF PHYTOPHTHORA BOLL ROT AND ITS LETHAL TEMPERATURE

冬季用显微镜镜检患有疫病的棉铃种籽,能检查到棉铃疫菌的游动孢子囊或卵孢子,重病棉铃种籽所带的卵孢子比轻病棉铃种籽多。疫病占整铃面积1/4以上时,其中的种籽可分离到疫菌;疫病在铃面的面积较小时,在其种籽上未分离到疫菌。将疫病棉铃中的自然带病种籽、健铃种籽与疫菌混合,或土中接种疫菌后播种,都能在铃期表现烂铃,烂铃数比播种健铃种籽多:但8月少雨时,种籽带菌对铃期烂铃影响不明显。疫菌在55℃5分钟即死亡;按此温度用温水浸种应能杀灭种籽所带疫菌。

Sporangia or oospores of Phytophthora boehmeriae could be seen on cotton seeds from the infected boll by microscopes during winter time. Oospores on seeds from severely infected bolls were more than on those from lightly infected bolls. The fungi could be isolated from the seeds of a rotten boll with over 1/4 infective area but not from the seeds of a rotten boll with less infective area. The seeds from infected boll or health seeds mixed with inocula of P. boehmeriae could cause more rotten bolls than the seeds from health bolls did. The same result was abtained by inoculation of P. boehmeriae into soil. But, the intected seeds had no significant effect on the number of rotten bolls when there was less rain in August. The pathogen died at 55℃ in five minutes, and therefore, seed treatment with hot water at this temperature should be effective to kill the pathogen on seeds.