Variations in Colletotrichum gloeosporioides strains from mango.
Kajamuhan A., Wijeweera C., Bandara J. M. R. S.
Author Affiliation: Postgraduate Institute of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka.
Tropical Agricultural Research 12 : 412-415
Abstract : Anthracnose caused by C. gloeosporioides [Glomerella cingulata] is the major postharvest disease of mango (Mangifera indica). A study was carried out to determine and group morphologically, the forms of C. gloeosporioides from mango in Sri Lanka to understand the degree of pathogenicity of each strain. Isolates of C. gloeosporioides were obtained from mango fruits, leaves and inflorescence from various locations in Sri Lanka (Batticaloa, Vavuniya, Kurunegala, Kandy, Colombo, Anuradhapura, Dambulla, Matale and Ampara districts). After 10 days on potato dextrose agar at 30°C under continuous white light, characters of the colonies were examined, and were tentatively grouped as rapidly growing cultures with extensive grey-pigmented mycelium and slow growing cultures with deep orange pigmentation. The lengths and widths of at least 30 conidia per isolate were determined microscopically and were subjected to cluster analysis. The results of the pathogenicity test for each isolate showed that there are variations in the lesion sizes developed by different isolates of C. gloeosporioides. There was no positive correlation between the pathogenicity and the lengths/widths of the spores of different isolates. Cluster analysis based on the lengths and widths of spores divided the 26 isolates into 4 distinct groups at the median normalized distance0.8. The clustering pattern observed suggests that the C. gloeosporioides may have different races and cannot be grouped geographically in Sri Lanka. The reason for this may be due to the transportation of mangoes throughout the country.