OCCURRENCE OF NATIVE MICROBIAL ANTAGONISTS AGAINST POTATO CYST NEMATODES IN THE NILGIRI HILLS OF TAMIL NADU

Abstract

Three hundred and twenty eight fungus, 178 bacteria and 15 actinomycetes were isolated from the potato rhizosphere soil samples and cysts collected from 67 villages of Nilgiris District. The fungal isolates included 36 Trichoderma, 15 Paecilomyces, 8 Vericillium, 21 Fusarium, 16 Aspergillus and 71 unidentified fungal species, bacterial isolates included 45 Bacillus and 7 Pseudomonas species and actinomycetes included 15 Streptomyces species. The fungal isolates were screened for their antagonistic potential against the potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida based on positive reaction for chitinase activity, antibiotic production, inhibition of egg-hatching and egg parasitization. Positive reactions for chitinase activity, antibiotic production,  egg-hatching inhibition and egg parasitization were observed in Fusarium isolate KEUF 255, Paecilomyces isolates NDPL 145, NDPL 264, MOPL 122, THPC 166 and DKPC 132 and Trichoderma isolates NDTH 343, NDTV 364, MOTV 164, EPTV 172, IRTX 176, TKTX 165, BGTV 175 and PNTV 168. They also exhibited the antagonistic potential against Phytophthora infestans in dual plate technique. The bacterial isolates were screened for their antagonistic potential against PCN based on positive reaction for chitinase activity, antibiotic production, acid production, HCN production, egg-hatching inhibition and egg parasitization. Bacillus isolates KEBX296, EPBX147, BGBX135 and KOBX134 expressed positive reactions. Investigation suggests that the virulence of naturally occurring microbial antagonists could be exploited as potential candidates for the management of potato cyst nematodes in the Nilgiri hills of Tamil Nadu.