Differences in pathogenicity among the three species of Colletotrichum on excised leaves, twigs, and branches of Dalbergia sissoo

Sissoo (Dalbergia sissoo Roxb.) is an economically and environmentally important tree species in South-East Asia. Colletotrichum gloeosporioides was reported to cause leaf blight disease in D. sissoo in 2021 in Sylhet, Bangladesh. Additionally, C. fragariae and C. siamense were reported to cause disease in Hopea odorata and Dipterocarpus turbinatus in 2021 and 2023, respectively, in Sylhet, Bangladesh. Here, we examined the variation in pathogenicity among the three species of Colletotrichum on detached leaves, twigs and branches of D. sissoo. Mycelial agar plugs of the Colletotrichum species were used to inoculate leaves, twigs, and branches of D. sissoo. The findings of this study demonstrated that C. gloeosporioides developed the highest lesion length (12.91mm) on inoculated leaves as compared to the other two species of Colletotrichum used, while C. siamense was the most virulent fungi species on inoculated twigs and branches in terms of lesion length (58.75mm and 48.36mm) followed by C. fragariae (50.38mm and 37.01mm) and C. gloeosporioides (41.2mm and 26.46mm), respectively. In general, C. siamense was the most virulent fungi species among the tested fungi species. The findings of this study showed that the Colletotrichum species which are not host-specific to D. sissoo may pose a threat to D. sissoo equally in future. Further studies are necessary to understand the spread of these pathogens to tree species in other locations in Bangladesh.