Variation in Virulence and Cross Infectivity Potential of C. Gloeosporioides Isolates Infecting Tropical Fruits

Abstract

Fruits of six different types viz. mango, pomegranate, mandarin, sweet orange, guava and custard apple were inoculated with 30 isolates of Colletotrichum gloeosporioides penz. Obtained from seven fruit hosts grown in four agro ecological zones of Maharashtra by following mycelial bit inoculation method by adopting FCRD analysis. Out of 126 possible interactions, 84 interactions exhibited compatible reactions with significant variation in virulence index and preference of host (fruit). Only one isolate Cg 68 (from mango) could able to infect all the six fruit types but with variable intensity and this isolate was identified as non- host specific. It was followed by Cg 71 from guava fruit which infected all fruit types except mango. Remaining isolates infected at least two fruit types. However, none of the isolates was found to be host specific. Twenty one isolates under study showed less specificity towards pomegranate and mango as compared to other fruit hosts. Isolate Cg 71 from guava recorded maximum mean disease reaction index of 6.76 irrespective of the hosts. Isolates Cg 64 and Cg 68 which were derived from mango were statistically un differentiable with respect to their mean disease reaction index. Isolates Cg 11, Cg 21 and Cg 61 from areca nut cashew, and mango respectively expressed very low degree of virulence and were rated as a virulent. Mandarin and mango were found to be more susceptible than other fruit hosts and were statistically on par. It was followed by pomegranate and sweet orange. This indicated that mango and mandarin fruits are more susceptible to post harvest fruit rot caused by C. gloeosporioides. Isolate Cg 82 which was basically obtained from pomegranate, showed greater infectivity on mango fruits than pomegranate.