VIRULENCE OF SYMBIOTIC BACTERIA ASSOCIATED WITH ENTOMOPATHOGENIC NEMATODES FOR INSECT PEST MANAGEMENT
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Date
2013
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PAU Ludhiana
Abstract
The studies on the virulence of symbiotic bacteria associated with EPNs were carried out on five EPN strains (N-12, N-13, N-14, N-15 & N-17) isolated form Punjab soils. Bacterial isolates (1, 2, 3, 4 & 5) from local EPN strains produced brick red coloured colonies and were non-bioluminescent. The infective juveniles (IJs) of each EPN strain developed into adults within 72 hours, when fed on respective bacterial isolates. This confirmed the association between bacterial isolates and respective EPN strains. The dendrogram developed based on RAPD-PCR analysis established that isolates 2, 4 and 5 are very closely related (94% similarity). However, isolates 1 and 3 (65% similar) are different from other three isolates. Based on sequence homology of 16S rDNA region of all bacterial isolates, the bacterial isolate 1 was identified as Delftia acidovorans, isolate 2 as Brucella spp., isolate 3 as Pectobacterium cypripedii, isolates 4 and 5 as Chryseobacterium indologenes. As all the bacterial isolates were different from most commonly occurring symbiotic bacteria (Xenorhabdus and Photorhabdus) with EPNs, thus four local EPN strains were identified based on ITS (internal transcribed spacer) region. All local EPN strains showed a maximum identity with new EPN genera viz. Heterorhabditidoides sp. RG081015 (88% similarity) followed by Rhabditis sp. Tumian-2007 and Heterorhabditidoides chongmingensis. This is the first record of a new species/genera of EPN isolated from India, which is very closely related to Heterorhabditidoides based on ITS region. In the bioassay experiment, none of the bacterial isolates was found effective for management of tobacco caterpillar, Spodoptera litura (Fabricius).
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