A novel chitosan biopolymer based Trichoderma delivery system: Storage stability, persistence and bio efficacy against seed and soil borne diseases of oilseed crops

Management of seed and soil borne fungal plant pathogens using fungal species belonging to the genus Trichoderma is gaining importance. Seed coating with powder based formulations of Trichoderma is most widely adopted by the researchers and farmers as well. Delivery system that leads to good adherence of fungal propagules on seed surface, minimizing the wastage of active ingredient, sustained and timely release during treatment process is very important for effective season long protection. Chitosan-PEG (Polyethylene glycol) (Cts-PEG) blend containing Trichoderma harzianum (Th4d) (Cts-PEG-Th) spores is developed and its storage stability, persistence in soil and bio efficacy against seed and soil borne pathogens of groundnut and safflower crops is studied. The blend was stable without much changes in pH throughout the storage period. Persistence studies conducted for 3 months revealed that Cts-PEG-Th amended soil, Trichoderma got released from polymer film slowly and reached a maximum of log 8 CFUs by 30 days and there after started declining to retain log 6 CFUs at 90 days. In shelf life study, the chitosan blend was able to maintain Trichoderma counts of log 10.0 and log 10.2 over a period of 6 months at storage temperatures of 30 degrees C and 4 degrees C, respectively and the antagonistic activity unaffected against three plant pathogens viz. Macrophomina phaseolina, Fusarium oxysporumf. sp.ricini and Aspergillus niger over a period of 6 months of storage. Bio efficacy testing in germination towels and green house pot studies revealed the effectiveness of seed treatment with Cts-PEG-Th blend significantly increasing the germination and seedling vigour and reducing the diseases in groundnut (peanut) and safflower.