Identification, Detection And Nuclear Behavior In Appressorial Formation Of Colletotrichum From Strawberry

Strawberry anthracnose is one of the most serious diseases of strawberry in the world, caused by Colletotrichum spp., including C. gloeosporioides, C. fragariae and C. acutatum. Among them, C. acutatum is considered as a quarantine organism in most countries in the world including China. Although there are some reports on strawberry anthracnose in China, there is no systemic study until now. Here we mainly report the results of morphological and molecular identification for Colletotrichum spp. from Zhejing and Shanghai, and the nuclear behavior during the appressium formation..The isolates of Colletotrichum spp. were obtained by tissue isolating, incubating diseased organ in moist condition and incubating after freezing treatment from strawberry field in Shanghai, Jiande and Hangzhou in Zhejiang. Based on the morphological characterization, 35 isolates were selected to compare and analyze the ITS sequence of rDNA. The results confirmed C. acutatum occurred in our country, but C. gloeosporioides and C. fragariae cannot be distinguished from each other by this method.Using freezing method to detect commonly existed Colletotrichum spp in symptomless strawberry plants, we found that strawberry leaves with highest frequency of colonization is from Jiande, of which, the percentage of C. acutatum is about 58.33%, followed by Hangzhou(Xiasha and Zhejiang Agricultural Academy), but no C. acutatum is detected. In Shanghai, the frequency of colonization is the lowest, but C. catutam is also detected. Using freezing method to diagnosis latent infection, we find that after 3 days' incubation, conidial mass began to form and after 5 to 7 days, all the colonized pathogens can be detected by conidial mass's formation. The relation between leaf part and colonization frequency had been observed, which indicated that the pathogens colonized mainly in the middle part of the leaf, 1cm away from the margin. The results provided the ways to sample and trace latent infection of Colletotrichum on strawberry by molecular method.Dynamic changcs of nuclear behavior were visualized during appressorial...