Significance of Microsclerotia in the Epidemiology of Black Pepper Anthracnose and an Approach for Disease Management in Nurseries

Abstract

Anthracnose incited by Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. is a wide spread and economically important disease of black pepper. In the present study, role of microsclerotia (MS) in the trans-seasonal perpetuation of C. gloeosporioides was investigated. Microscopical examination of the runner shoots exhibiting necrotic lesions revealed the presence of dark, melanized structures which resembled MS. The excised necrotic regions when subjected to high humidity produced acervulus with setae. Under in vitro conditions, C. gloeosporioides produced MS predominantly on the aerial surface as inseparable congregations, enmeshed in the mycelial mats in potato dextrose broth and as individual units 7–8 days after incubation on glass slides. Sequential events in the formation of MS included germination of conidia, formation of conidial anastomosis tubes, aggregation of hyphae, and the formation of melanized microsclerotial bodies. Three types of microsclerotial germination were observed under in vitro conditions viz., sporogenic, myceliogenic and both. PCR confirmation with CgInt species-specific primer and ITS4 resulted in 450-bp amplification. Since, runner shoots are predominantly used as propagating material in black pepper, an approach was devised to manage anthracnose under nursery conditions by treating the 2- to 3-node cuttings (nursery planting material) with carbendazim (12%)—mancozeb (63%) @ 0.1% for 30 min. The results of the study suggests a new facet in the disease cycle of black pepper anthracnose, indicating that the pathogen survives as microsclerotia in planta and could act as a potential source of inoculum