Asian Journal of Research in Biosciences

Endophytic bacterial consortia assist plant growth by various secretions in a mutualistic relationship. Studies deciphering such relationships may be meaningful as they explore novel alternatives for agricultural chemical inputs which would otherwise pollute the nature. Hence, an attempt was made to examine the plant-growth-promoting (PGP) potentials of leaf bacterial endophytes from selected medicinal herbs and also their potential to impede the growth of leaf spot disease pathogen Pithomyces atro-olivaceous isolated from Arachis hypogaea L. A total of 10 distinct bacterial morphotypes were isolated from medicinal herbs such as Catharanthus roseus, Phyllanthus amarus, and Ocimum tenuiflorum. All the endophytes were screened for plant-growth-promoting traits and observed to secrete Ammonia (NH₃) (at 90%), Lipases (at 90%), Proteases (at 60%), Siderophores (at 40%), Amylases (at 20%), Chitinases (at 40%), Hydrogen Cyanide (HCN) (at 70%), Indole 3-Acetic Acid (IAA) (at 70%), Cellulases (at 40%), and Phosphate solubilisation (at 10%), followed by antifungal activity against Pithomyces atro-olivaceous (at 10%). We observed Rothia spp., Staphylococcus spp., Lactobacillus sp., Micrococcus sp., Bacillus sp., Propionibacterium spp., and Actinobaculum sp. as leaf endophytes based on biochemistry and the potent isolate was identified as Staphylococcus hominis subsp. novobiosepticus strain KE6 based on 16S gene sequence homology. A marked increase in the total amount of chlorophyll, sugars and protein content, biomass yield and vegetative growth parameters were observed upon 30 days’ post inoculation through induced cuts in mature groundnut leaves and the outcomes were statistically analyzed and represented graphically. In addition, suppression of leaf spot disease symptoms was observed from second day post spraying the endophytic bacterial preparations in the form of foliar sprays. To the best of our literature survey, this study stands as the first report on the interplay of endophytic bacterium, Staphylococcus hominis subsp. novobiosepticus as a potent plant growth promoter and an antagonist to control fungal leaf spot disease in groundnuts caused by a unique strain of Pithomyces atro-olivaceous and has opted medicinal plants as its desirable ecological niche.