Histopathological Study of Infection Process of Colletotrichum gloeosporioides Penz and Sacc. on Mangifera indica L.
Anthracnose, caused by Colletotrichum gloeosporioides, is a serious postharvest disease of mango. The histopathological studies on anatomy of naturally infected by Colletotrichum gloeosporioides and artificially inoculated leaves and healthy leaves were performed to understand the infection process of anthracnose at various intervals after inoculation. Germination and penetration processes of the pathogen within the whole leaf were observed. The first evidence of penetration into the whole leaf was observed 48 h after invasion. It also revealed that mycelia were prominent after 120 h after invasion by the fungus (C. gloeosporioides). Subcuticular infection by hyphae was present in transverse leaf sections (T.S.) of the diseased sample after 72 h. Also, both inter and intra-cellular hyphal invasion were observed after 72 h. Mesophyll cells were highly affected by fungal invasion and rapidly collapsed. Swelling of epidermal cell walls was also observed. After 96 h almost all the cells became necrotized (Nc). Necrotized mycelial mats (M) of C. gloeosporioides was observed after 120 h and all the invaded cells became necrotized (Nc) forming a spot which eventually the cells ruptured leaving a shot hole symptom. All these observations pertained to the cells of mesophyll tissue indicating that these are the regions of fungal invasion and host tissue damage resulting in the disease symptoms. Naturally infected and artificially inoculated (in vitro) presented no significant differences suggesting that the pathogen invasion and symptom development process is similar in both the conditions.
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