Morphological and molecular characterization of two devastating chilli pathogens Colletotrichum acutatum (Chilli die-back/ Anthracnose) and Fusarium brachygibbosum (Chilli wilt)

Among all of the spices and condiments, the chilli (Capsicum annum L.) is the fourth most important around the world. Within Asia, it has been established as most important spice. Out of more than forty diseases incited by fungi, the chilli die-back/anthracnose and wilt disease caused by Colletotrichum spp. and Fusarium spp. respectively have been established most serious constraint in the chilli production especially in India. The cultural and morphological characteristics studies revealed that the colony C. acutatum had smooth margin with white to greyish-black zonation. The topography of mycelia was raised fluffy mycelial growth with dense crowding. The microscopy work revelaed that C. acutatum produced fusiform conidia with a size ranged from 8.3 μm to 9.6 μm length and 3.6 μm to 4.7 μm width. On the other hand, the colony colour of Fusarium isolate was pinkish white to white with browned tinch smooth to irregular margin. The mycelial topography was flat to fluffy. Following the microscopy studies, koch postulates for pathogenicity were also followed by both pathogens positively. Furthermore, universal ITS primers-based molecular characterization were carried out for both chilli pathogens. The results revealed that PCR amplification of ITS gene region for both pathogens resulted in an amplicon fragment of 550 bp and 560 bp while in the F. brachygibbosum analogous to the region of the 18S-28S rRNA intervening sequence. Later, the respective amplicons were sequenced followed by sequence-submission in the NCBI database with accession numbers of MF063316 and MF150000 respectively. Therefore, in this present study, the C. acutatum and F. brachygibbosum pathogens were identified based on its cultural, morphological and molecular characteristics.