Sporopollenin-chitosan microspheres loaded with an endophytic fungus Talaromyces neorugulosus R-209 for promoting development and controlling root rot in pigeon pea.

Plant-beneficial microbes can be effective as biological agents for promoting development and controlling diseases in plants. However, direct inoculation of non-encapsulated plant-beneficial microbes into the soils can affect their vitality and efficacy. A novel bio-based encapsulant, sporopollenin-chitosan microspheres (SCMs), was developed to load an endophytic fungus Talaromyces neorugulosus R-209 with antagonistic activities against the root rot pathogen (Rhizoctonia solani AG4) and plant growth-promoting functions. The results showed that T. neorugulosus R-209 encapsulated in SCMs (TnR-209-SCMs) could significantly enhance fungal spore germination rates and available nitrogen/phosphorus levels in the soil compared to the non-encapsulated fungus. In addition, the preliminary evidence suggests that TnR-209-SCMs have a basic safety profile for practical applications. Inoculation with TnR-209-SCMs could effectively promote development and enhance resistance in pigeon pea seedlings by promoting chlorophyll synthesis, improving photosynthesis, and enhancing phenolic compound accumulation. Meanwhile, T. neorugulosus R-209 was found to endogenously colonize root intercellular spaces. Moreover, co-inoculation of TnR-209-SCMs and R. solani AG4 could reduce host defense responses compared to R. solani AG4-infected roots, as reflected by lower levels of phenolic compound accumulation and pathogenesis-/biosynthesis-related gene expression. Overall, TnR-209-SCMs is a promising biological agent that can promote development and control root rot in plants, which also provides an innovative approach to biomaterial-supported agricultural practices.