In-vivo Evaluation of Agro-Waste based Formulations of Yellow Pigment Producing Actinobacteria against Mulberry Root Rot Pathogens

Abstract

Mulberry is a multipurpose deciduous tree mainly cultivated for silk cocoon production. The continuous cultivation focusing on high yield made the crop prone to various diseases, especially root rot. To evade the detrimental effects of agrochemicals on sensitive silkworms and environment, the importance was given to bio-control approach. In the present study, four bio-formulations of the actinobacterial isolate NM5 (Streptomyces parvulus) were prepared using three carriers: talc, rice husk ash and spent silkworm pupal powder. From the in-vivo study against combined inoculation of root rot pathogens, the lowest incidence of disease symptoms including wilting (25.45%) and rotting (20.91%) was observed in APNM5 (rice husk ash: silkworm pupal powder- 1:1 ratio) treated plants which scored as mild to moderate infection. Untreated control was stunted with chlorotic leaves that defoliated prematurely with severe infection (76.25% wilting and 82.80% rotting). Moreover, in all NM5 treated saplings, as a result of defense action rotten root portions were stimulated to develop new healthy rigid roots. Biometric observations showed formulations had positive effect on plant growth parameters even in the presence of pathogens including higher leaf numbers (27.5), enhanced leaf area (67.96 cm2) and yield (6 g plant-1), shoot length (44.56 cm) and weight 25.50 g plant-1), root length (33.67 cm), root weight (2.17 g plant-1), root: shoot ratio (0.08) than uninoculated saplings. Therefore, both the performance of potential isolate and effective utilization of agro-waste were enhanced by the nutrient based APNM5 bioformulation in an eco-friendly way.