Functional Diversity of Bacterial and Fungal Endophytes Associated with Mulberry (Morus spp.) Cultivated in Southern Karnataka, India

Abstract

Mulberry (Morus spp.) cultivation is frequently constrained by both abiotic and biotic stresses, including insect pests and diseases, which adversely affect silkworm health and silk productivity. Endophytes, defined as microorganisms that colonize internal plant tissues without causing visible harm, represent a promising but underexplored biological resource for enhancing plant vigour, stress tolerance and nutritional quality. The present study evaluated the diversity of bacterial and fungal endophytes associated with eight mulberry varieties grown under field conditions in southern Karnataka, India, and assessed their potential implications for mulberry growth and silkworm biology. Endophytic microorganisms were isolated from surface-sterilized leaf and shoot tissues using standard culture-dependent techniques. A total of four dominant endophytic genera were consistently recovered across samples, including Bacillus spp. among bacteria and Aspergillus spp., Trichoderma spp. and Fusarium spp. among fungi. The frequency and distribution of these endophytes varied among mulberry varieties and between plant tissues, indicating clear host genotype- and tissue-specific colonization patterns. In general, shoots harboured comparatively higher fungal diversity, while bacterial endophytes, particularly Bacillus spp., were more consistently distributed across both tissues. Although quantitative data on isolation frequency and abundance are presented in the results section, the observed patterns indicate differential colonization efficiency among mulberry genotypes. The dominance of Bacillus and Trichoderma suggests potential plant growth-promoting functions, including improved nutrient availability, enhanced physiological activity and increased stress tolerance of host plants. These microbial interactions are likely to influence mulberry leaf quality, a critical determinant of silkworm growth performance and cocoon traits.