Ingestion of bacteria expressing dsRNA to maggots produces severe mortality and deformities in fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is the world’s most damaging (30–100%) pest infesting important fruits and vegetables. Its control is highly challenging due to its polyphagous, multivoltine nature, and unexposed developmental stages. No known fruit fly-resistant guava germplasm is reported so far worldwide. RNAi approach in guava against fruit fly can provide an attractive alternative to overcome this problem. Escherichia coli-based dsRNA expression strategy was used to investigate its potential in control of B. dorsalis via targeting its two vital genes, ecr (ecdysone receptor) and rpl19 (a ribosomal protein L19). Effects of feeding E. coli, HT115 (DE3) expressing dsRNA of Bdecr and Bdrpl19 with artificial diet to maggots of B. dorsalis resulted in severe mortality and deformities in treated maggots, emerged pupae, and adults. Total mortality (including deformity) of maggots, pupae, and adult fruit flies was 86.3% and 87.9% and was highest in 700 μl (× 200 of 3.5 × 108 cells) dsRNAs of Bdecr and Bdrpl19 bacterial treatment respectively, compared to 350 and 200 μl bacterial treatments. Severe defects in terms of developmental changes like melanisation and deformities of maggots and pupae, absence of wings, underdeveloped abdomen/absence of complete abdomen, absence of legs, severely curled wings, malformed legs, and incomplete eclosion, and suppression of these target genes expression were observed in emerged adults. The study provides a proof of concept of feasibility to silence two potential genes by feeding bacteria expressing dsRNA in all developmental stages of B. dorsalis to step further to perform RNAi-based pest control.