A Review on Colletotrichum spp. Virulence mechanism against host plant defensive factors
Colletotrichum species are a group of pathogenic fungi that devastate farmers around the world and causing huge loses in crop production worldwide. The pathogen is the major causative agent of anthracnose disease that is affecting a wide range of crops. The disease is common in the tropics and sub-tropic regions but some species have been found to inhabit the Mediterranean climate. Control of Colletotrichum has proved to be a challenge due to its ability to develop new infection strategies that enables it to overcome the host inhibitory mechanisms. This paper therefore aimed at reviewing the virulence mechanisms of the pathogen to enable it to overcome the plant defensive mechanisms. From the different reviews it came out clearly that the pathogen infection encompasses the differentiation of specialized cell types that are associated with penetration, growth inside living host cells and colonizing with killing (bio trophy) and tissue colonization and destruction (necrotrophy). The fungi also produce some of the proteins and enzymes that aid in their penetration and attack of the host. Some of the enzymes that release by these species of fungi are cellulases that catalyses the degradation of host cell, pectin lytic enzyme, endo-polygalacturonases, protein kinases, glucanase and chitins. The fungi also secrete protein effectors that enable them reprogram the host cell immunity factors. Further virulence mechanism of Colletotrichum species is the power to modify the secondary antimicrobial compound the phenolics to less inhibitory compounds for example conversion of phaseollin to 1a-hydroxyphaseollone. Other contributing factors to the success of Colletotrichum attack on the host plants is the production of chemicals such as; colletotric acid, ergosterol, Colletotrichum and colletruncoic acid methyl ester.