Actinoalloteichus cyanogriseus: a broad spectrum bio-agent against mulberry root rot pathogens

Abstract

Background: In India, severe yield and economic losses in sericulture were reported due to mulberry root rot disease. Since the disease was caused by complex soil-borne pathogens with wide host range, an attempt was made to develop actinobacteria based biological management strategy to mitigate it. Results: As a result of continuous screening for anti-fungal actinobacteria, 2 novel and potent isolates (M11 and M12) belong to the rare genus, Actinoalloteichus were obtained from mulberry rhizosphere. Both isolates were gram positive, grayish, aerobic and produced good amount of melanin pigment during sporulation. They exhibited excellent anti-fungal activity against mulberry root rot pathogens viz., Macrophomina phaseolina, Lasiodiplodia theobromae, Fusarium solani, Sclerotium rolfsii and Rhizoctonia solani. In addition, these melanogenic isolates grew in wide temperature and pH ranges. Their multi-stress tolerance ability/polyextremophilic nature was exposed when amending regular growth medium with excess concentration of salt and alkali. In addition, the potent isolates also showed tolerance to carbendazim (up to 1000 ppm) and UVB irradiation (up to 180 min at 10 cm distance). Conclusion: The present study focused on the identification and characterization of melanogenic actinobacteria, further made it potential candidate that could be incorporated in eco-friendly, integrated disease management strategies against complex mulberry root rot pathogens.