Isolation, genetic diversity and identification of a virulent pathogen of eriophyid mite, Aceria guerreronis (Acari: Eriophyidae) by DNA marker in Karnataka, India

Abstract

Aceria guerreronis is a serious pest of coconut in India. Investigations were carried out to investigate fungal pathogens infecting the eriophyid mites for their utilisation as biocontrol agents in Karnataka, India. The fungal pathogens namely, Hirsutella thompsonii, Beauveria bassiana, Fusarium semitectum and few opportunistic pathogens namely, Fusarium moniliforme, Cladosporium tennuissimum, Aspergillus niger, Penicillium sp. and Mucor sp. were collected from eriophyid mite populations in different parts of Karnataka area. Of the total collected nuts, 3.54% were infected by H. thompsonii, 2.46 and 0.29% by B. bassiana and F. semitectum, respectively. A lower number of nuts (0.03 to 0.79%) were infected by opportunistic pathogens. The incidence of pathogen infected coconuts in areas with lower temperature and higher humidity were ranged from 4.37 to 19.52% whereas with higher temperature and lower humidity it was 0 to 4.54%. Occurrence of B. bassiana and F. semitectum on A. guerreronis are new records. Among isolates of H. thompsonii collected from different places, the isolate Bangalore was more virulent followed by Mysore, Mandya, Kanakapura, Arsikere and Hiriyur isolates, as it recorded maximum infection (HTCMBAN- 88.63%). The B. bassiana isolates caused mortality ranging from 72.87 to 86.97%. The virulent isolate H. thompsonii (HTCMBAN) was tested at different concentrations, with increase in the concentration mortality rate. The genetic diversity of isolates of H. thompsonii by random amplification of polymorphic DNA (RAPD) revealed that grouping of the isolates was in accordance with geographic location. DNA fragments of 850 and 950 bp (OPA-20) were specific to the virulent isolate HTCMBAN.

Key words: Fungal pathogens, eriophyid mites, genetic diversity, DNA marker.