Identification of a Pathogen from Bipolaris Leaf Spot Disaese of Coconut and Its Biological Characteristics

In October 2012, a new leaf spot disease was observed on coconut seedlings in Wenchang, Hainan province. Based on microscopic observation, the conidiophores were slightly flexuous or straight, produced curved,spindle-shaped or fusiform, septate conidia with 5 to 9 pseuedo-septa. Thus, the pathogen belong to Bipolari. sp.Furthermore, the result of ITS sequence analysis revealed 99% sequence similarity with B. setariae. The results of biological characteristics showed that CAM and PDA medium were the best for the mycelial growth of pathogen.Temperature ranged from 20 to 30 ℃ were optimum for its mycelia growth, and conidia germinated best on 30 ℃.p H ranged from 4 to 11 was optimum for its mycelia growth. The mycelia grew best on media with sucrose as C source. Peptone nitrate and was the best nitrogen sources for mycelial growth and the(NH4)2HPO4nitrate was the second. Continuous light was the best for mycelial growth. The lethal temperature was 56 ℃, 15 minutes for hypha growth and conidiospore.