Cross infectivity of Colletotrichum spp. on tropical fruit crops and Ageratum spp. (weed host) in Southern Karnataka and Andhra Pradesh

Abstract

Species of Colletotrichum are associated with many host plants of diverse ecosystems including tropical, sub- tropical and temperature climatic conditions. Isolates of Colletotrichum were obtained from orchards of cultivated tropical fruit crops in Andhra Pradesh and Southern parts of Karnataka, India.Cross infectivity studies proved the wide host range of different isolates in seven fruit crops and one weed host (Ageratum spp.) tested. Most of the isolates displayed high virulence on seven alternative fruit crops and Ageratum spp. also. IIHR_COL_C6 isolated from mango recorded high virulence on guava fruits than other isolates. IIHR_COL_C8 displayed unique nature with cross infection i.e., except on the original host isolated from, it showed least infection on all other alternative hosts tested showing its host specificity. Isolates IIHR_COL_C2, IIHR_COL_C3, IIHR_COL_C6, IIHR_COL_C7 and IIHR_COL_C9 recorded high virulence on their original hosts of isolation viz., banana, custard apple, mango, papaya and pomegranate respectively indicating the adaptation to main host and less preference of alternative hosts. A weed host Ageratum spp.was tested for its susceptibility to Colletotrichum isolates and found to be susceptible to all nine Colletotrichum isolates in the artificial inoculation. Most virulent isolates were IIHR_COL_C7 and IIHR_COL_C1 isolated from papaya and banana (4.76 cm and 4.68 cm), indicating the ability of Colletotrichum spp. in colonizing weeds. Isolates of Colletotrichum spp. from tropical fruit crops in this study can cause disease and might survive in off season alternatively on other fruit crops and also on weeds.