High yield and quality silk fibre production by muga silkworm, Antheraea assama through application of plant growth promoting rhizobacteria

Plant growth promoting rhizobacteria (PGPR) were isolated from the rhizosphere of som plants (Machilus bombycina) maintained at the experimental farms of Central Muga Eri Research and Training Institute, Lahdoigarh, Jorhat. Microbial isolates were characterized and screened for effectiveness by spraying combinations of strains on the som plants. Selective and specific functional compatibility relationships in plant response between the microbial inoculants were observed. The effects of the PGPR combinations through increase in chlorophyll content, free amino acid, total protein, reducing sugar, carbohydrate and dry weight were studied. Five strains showing growth-promoting activity were selected and all the combinations had positive effect on the biochemical parameters studied, but the combination of RB1 + RB3 + RB4 + RB5 + RB8 strains produced the best result. Muga silkworm larvae fed on som leaves of the plant treated with this strain combination had higher activity of the enzymes, viz. trehalase, transaminase and phosphorylase in the silk gland, haemolymph and fat body. The cocoons of these silkworms produced more silk in terms of quality and quantity. This study could be exploited for improvement in quality and quantity of silk production through the application of PGPR.