Yoshida S, Shirata A
National Institute of Sericultural and Entomological Sciences, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan.
Plant Dis. 1999 May;83(5):465-468. doi: 10.1094/PDIS.1999.83.5.465.
Overwinter survival of Colletotrichum dematium, the causal agent of mulberry anthracnose, was examined in Japan. Conidia and infected mulberry leaves were mixed with soil and placed on the ground in early December. Viability of conidia declined rapidly under field conditions-they could not be recovered within 30 days-whereas conidia placed indoors or outdoors under a roof protected from rain and snow survived longer. When a suspension of soil infested with conidia was used to inoculate detached healthy leaves, no infection was detected after 65 days of incubation, suggesting that conidia in soil are not a significant form of overwintering inoculum. When infected or latently infected leaves incubated in soil under field conditions were used as inoculum on leaves, it was shown that the fungus remained viable for at least 150 days. The fungus in infected leaves maintained under laboratory conditions at different temperatures survived for at least 90 days at 25 and 35°C and for 600 days at 0°C. These results suggest that C. dematium can overwinter in infected or latently infected leaves, and that these leaves can be a source of primary inoculum the following year. Hence, the elimination of fallen leaves in the field in autumn may be an effective way to prevent occurrence of the disease the following year.
在日本，对桑炭疽病病原菌——盘长孢状刺盘孢菌的越冬存活情况进行了研究。分生孢子和感染炭疽病的桑叶与土壤混合，并于12月初放置在地面上。在田间条件下，分生孢子的活力迅速下降——30天内就无法再分离得到——而放置在室内或有防雨雪屋顶的室外的分生孢子存活时间更长。当用含有分生孢子的土壤悬液接种离体健康叶片时，培养65天后未检测到感染，这表明土壤中的分生孢子不是越冬接种体的主要形式。当将在田间条件下于土壤中培养的感染或潜伏感染的叶片用作叶片接种体时，结果表明该真菌至少存活150天。在实验室不同温度条件下保存的感染叶片中的真菌，在25℃和35℃下至少存活90天，在0℃下存活600天。这些结果表明，盘长孢状刺盘孢菌可在感染或潜伏感染的叶片中越冬，且这些叶片可能是次年初侵染接种体的来源。因此，秋季在田间清除落叶可能是预防次年该病发生的有效方法。
