Influence of Bactrocera Dorsalis Larval Gut Bacteria on its Susceptibility to the Entomopathogenic Fungus, Metarhizium Anisopliae

Abstract Symbiotic interactions between insects and bacteria have been associated with a vast variety of physiological, ecological and evolutionary consequences for the host. A wide range of bacterial communities have been found in association with the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), an important pest of cultivated fruit in most regions of the world. We evaluated the diversity of gut bacteria in B. dorsalis specimens from several populations in Kenya and investigated the roles of individual bacterial isolates in the development of axenic B. dorsalis fly lines and their responses to the entomopathogenic fungus, Metarhizium anisopliae. We utilized a high throughput sequencing approach of the bacterial 16S rRNA gene to evaluate microbiomes, coupled with culture and mono-association for the assay. The shortest embryonic development period was recorded in flies with an intact gut microbiome while the longest period was recorded in germ-free fly lines. Similarly, larval development was shortest in flies with an intact gut microbiome. Adult B. dorsalis flies emerging from embryos inoculated with a strain of Lactococcus lactis had decreased survival when challenged with a standard dosage of M. anisopliae ICIPE69 conidia. However, there were no differences in survival between the germ-free lines and flies with an intact microbiome. These findings contribute to the selection of probiotics used in artificial diets for B. dorsalis rearing and the development of improved integrated pest management strategies based on entomopathogenic fungi.