Abstract

Grape anthracnose caused by Sphaceloma ampelinum is one of the most common fungal disease of grape in Thailand. The objective of this study was to examine the morphological diversity among Sphaceloma isolates from grapes and compare their pathogenicity and virulence on a susceptible grape cultivar. 24 isolates of Sphacelomawere isolated from diseased grape samples collected from different geographical regions of Thailand. Their colony morphology consisting of surface texture, elevation, aerial mycelium production, size and coloration were studied along with their conidial size. Subsequently 11 representative isolates having the same morphology were compared for their pathogenicity and virulence on Black Queen susceptible grape cultivar. According to the colours, the 11 isolates could be divided into 8 groups. The average colony size on potato dextrose agar measured at 35 days was 3.70 ± 0.10 × 3.82 ± 0.08 cm. Most isolates produced single – celled, hyaline, cylindrical shaped with rounded – end conidia containing a cellular gutter inside. The average conidial size was 2.1 to 3.6 × 3.4 to 6.7 µm. From the 11 isolates tested on Black Queen grapes, only 7 isolates had pathogenicity with different degree of virulence. Among the isolate GSH from the SUT farm, Nakorn Ratchasima was the most virulent.

Key words: Anthracnose, grape, colony morphology, fungal characterization,Sphaceloma ampelinum.