DIVERSITY OF SPHACELOMA AMPELINUM, CAUSAL PATHOGEN OF GRAPEVINE ANTHRACNOSE IN THAILAND

Anthracnose and downy mildew are major diseases of most grapevine (Vitis vinifera) cultivars grown in Thailand. Isolates of Sphaceloma ampelinum, the anamorph stage of Elsinoe ampelina, were collected from grapevine foliar in Nakhon Ratchasima, Ratchaburi, Chiang Rai, Prae and Chonburi, Thailand by directly plating infected tissues onto water agar and the fungus was subsequently transferred and cultured on potato dextrose or cereal agar (PDA or CA) medium. Single-spore isolates were obtained and cultured on PDA, CA, corn cereal agar (CCA) and Job's tears corn cereal agar (JCCA) developed in our laboratory to compare colony morphology. Morphological analysis of the fungus showed that various isolates could not be unambiguously distinguished based on colony size, color, appearance and conidial size. Moreover, color is not a stable characteristic over time. However, isolates from the same region appeared more morphologically related than the ones from different regions. Colonies sporulated faster when grown on JCCA. Five distinct isolates were used for pathogenicity analysis with 6 potential resistant hybrids and 3 susceptible cultivars. Differential pathogenic responses were observed among these genotypes. Better understanding the pathogen will allow efficient selection of breeding strategies for anthracnose resistance in Thailand.