Biodiversity of fruit flies Tephritidae Diptera and utilization of gut bacteria in their management

Abstract

Present investigations on biodiversity of fruit flies and their associated gut bacteria were undertaken to resolve the fruit flies spectrum prevalent in Himachal Pradesh and their molecular characterization along with associated gut bacteria. The results revealed that Bactrocera cucurbitae and Bactrocera tau are the major and serious pests of cucurbits causing 65.88 per cent fruit infestation in Himachal Pradesh. Out of 17 species of tephritid fruit flies recorded from 5 genera, 14 species were already present in Himachal Pradesh. Bactrocera latifrons (Hendel), B. nigrofemoralis White and Tsuruta, Dacus longicornis Wiedemann, Dacus sp., Cyrtostola limbata (Hendel) from subfamily Dacinae and Pliomelaena udhampurensis Agarwal and Kapoor from subfamily Tephritinae were recorded for the first time from Himachal Pradesh. Pest status and distribution of B. latifrons needs to be investigated in Himachal Pradesh as this species has been reported as pest in south India. Eight species of fruit flies (61 isolates) were molecularly characterized with mtCOI gene and were submitted to GenBank, NCBI with accession number HQ378195-HQ378245 and HQ446513-HQ446522. mtCOI gene/s of B. nigrofemoralis, D. longicornis and D. sphaeroidalis are totally new to GenBank, NCBI. mtCOI gene analysis of B. cucurbitae showed exceedingly low genetic diversity amongst B. cucurbitae populations and one single haplotype (H1) was found to be predominant in Indian subcontinent. On the basis of mtCOI gene sequence analysis of B. tau isolates from Himachal Pradesh, the observed genetic diversity is low and quite similar to B. tau sp A (Thailand). Eight species of fruit flies were clearly differentiated on the basis of mtCOI gene sequences which were grouped together as per earlier classification. This validates the utility of mtCOI gene as a tool for fruit fly detection, species characterization and phylogenetic studies. Out of 63 bacteria isolated from the gut of B. tau on two culture media viz. BHIA and PYEA, 30 bacteria were screened as attractant for fruit fly. Five most attractive bacterial isolates were characterized on the basis of morphological, biochemical and 16S rRNA gene sequence characteristics. These were Delftia acidovorans, Pseudomonas putida, Flavobacterium sp., Defluvibacter sp. and Ochrobactrum sp. Their 16S rRNA gene sequences were submitted to GenBank, NCBI and accession numbers HQ446523 to HQ446527 was awarded to them. Attractancy of different bacterial isolates was in the range of 6.17 to 11.17 and 5.67 to 8.17 adults/ 30min for female and male, respectively. P. putida was found to be the most attractive bacteria to fruit fly followed by D. acidovorans. All bacterial isolates were, however, found statistically superior over sugar (negative control) and inferior to protein hydrolyzate (positive control). Twenty two volatile chemicals were identified on the basis of GCMS analysis of five bacterial isolates. Of which only three chemicals viz. Z-(9)-tricosene (House fly), cedrol (Cryptomeria bark borer) and chryophllene oxide (Compoletis sonorensis) are known to be associated with insect chemical communication behaviour.