Efficacy of phototrophic bacterial feed supplementation on economic traits and disease resistance in mulberry silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Abstract

Sericulture, often known as silk farming is the practice of rearing silkworms for production of raw silk. One of the major impediments faced by the sericulture community is the silkworm diseases that cause significant crop losses. In the present study, the efficacy of phototrophic bacteria as feed supplements in improving the economic traits as well as disease resistance in mulberry silkworm, Bombyx mori L. was assessed. A total of three phototrophic bacteria were isolated and identified as belonging to the genera Marichromatium, Rhodobacter and Rhodopseudomonas based on 16S rRNA gene sequencing analysis. Their morphological, physiological and biochemical characters were studied, grown under ambient conditions and biomass was harvested. Mulberry fortified with the aforementioned phototrophic bacteria in solitude and combinations at varying concentrations (0.5, 1, 2 and 5%) were found to be innocuous to the mulberry silkworm. The best results were observed when mulberry leaf was supplemented with Rhodopseudomonas sp. at 2% concentration which improved survival, cocoon weight, shell weight, shell%, filament length and non-breakable filament length by 5.18, 0.27, 3.86, 3.5, 1.5 and 1.2%, respectively under normal rearing conditions. Under Staphylococcus sp. infected conditions, the aforesaid diet also enhanced survival in silkworms by 16%. On the other hand, the same diet didn’t exhibit any discernible influence on survival against fungal, viral, or microsporidian infections in silkworm.