The Etiology On Dioscorea Black Spot And The Disease Control

This paperreports the investigation of occurrence status in Liaoning province, the identification of pathogy, the incidence and epidemic rule, the biological characteristics and the control technology of Dioscorea black spot. The result is as following.1. The investigation of incidence and harm indicated that Dioscorea black spot was arised at large in the east mountainous planting area of Liaoning province. It mostly infected the leaves of Dioscorea nipponica Makino, causing leaf blight ahead of time and photosynthesis falling and fruit dematurated, and causing heavy losses as 20-30%.2. Identification of pathogy of Dioscorea black spot. Pure culture was isolated from the samples which were collected from the east mountainous planting area of Liaoning province in the past three years. According morphologic characteristics cultivated characteristics and infection, consulting《Plant Pathology》 edited by Lu Jiayun and 《Fungi Record in china》 edited by Zhang Tianyu, Dioscorea black spot was caused by Alternaria dioscoreae Vasant Rao which belongs to Deuteromycotina Hyphomycetes Dematiaceae Alternaria According to reports in home and aboard, Alternaria dioscoreae Vasant Rao mostly distributing in china and India was described by Vasant Rao in 1961. it was only reported in Shanxi and Shandong province, infecting yam mainly, and there was no report on it in Liaoning province.3. Studies on biological characteristics of Alternaria dioscoreae Vasant Rao. According to result consulted, there was no report on it. The result of biological characteristics of Alternaria dioscoreae Vasant Rao in this paper indicated: the temperature of germination for the conidia was 5-30℃ widely, the optimum was 20-25℃; the optimal RH was 100%; the optimal pH was 6-7; the optimal sugar source was saccharose D-fructose and D-amritose; the lethal temperature...