Evaluation of Substrates and Carrier Material for Shelf Life Studies of Streptomyces Bioformulation

Abstract

Biological control with potential actinomycetes is receiving greater attention all over the world. Among actinomycetes, Streptomyces being root-colonizing and a rich producer of secondary metabolites has become one of the important promising groups of antagonists.  Management of soilborne diseases using biocontrol agents is a sustainable option in agriculture. Studies were conducted on the collection and isolation of actinomycetes, their shelf life studies for formulation development using different substrates and carrier material.  Growth of actinomycetes on different media viz., Ken knights, Crawford broth, Starch casein hydrolysate broth and AFMS broth were observed.  To find a suitable carrier for long shelf life of formulation, different carrier material viz., Talc, Kaolinite, whaet bran, lignite and vermicompost were used. The paramount need and challenge in plant protection is the development of new, safe and more effective antifungal agents as bioformulation to control stem rot of groundnut and to improve pod yield. Collected 180 soil samples from the rhizosphere of groundnut in different growing zones of Andhra Pradesh and isolated 50 Streptomyces isolates.  In vitro dual culture studies by Sclerotium rolfsii with 20 isolates, five potential isolates (Ggd, Kdr, Kyd, Lrp and Mkc), were selected for morphological, cultural, biochemical and molecular characterization. Five identified Streptomyces species clustered with the Streptomyces reported from different parts of the world. Among the five identified Streptomyces species (Ggd, Kdr, Kyd, Lrp and Mkc), three potential isolates were selected for preparation of bioformulations. Five different formulations i.e., talc, kaolinite, lignite, wheat bran and vermicompost were prepared and evaluated for longer shelf life. It was found that talc based formulations were superior in maintaining the longer shelf life of the Streptomyces. The efficacy of talc-based formulations of Ggd, Kdr and Kyd were evaluated against S. rolfsii for their ability to reduce the stem rot incidence of groundnut under glasshouse conditions. seed treatment with talc based formulation of Ggd isolate @ 5g / kg seed + soil application @ 5 g / 5 kg soil at 30 DAS was found to be superior in reducing the stem rot incidence, significantly improved plant biometrics, yield and yield attributes in groundnut.