Castor oil-based waterborne polyurethane nanocoating enhances growth, stress tolerance, adhesion, and immune evasion of Beauveria bassiana

The WPU matrix promotes fungal growth, spore germination, and tolerance to UV, thermal, and chemical stresses. • WPU enhances conidial retention on maize leaves and improves insecticidal efficacy. • WPU-encapsulated conidia evade host immune recognition, reducing immune clearance and facilitating infection. • Transcriptomic analysis identified key genes and pathways associated with WPU-mediated growth promotion and UV resistance. Environmental fragility and host immune clearance remain major barriers to the field efficacy of entomopathogenic fungi in agricultural pest management. In this study, we developed a bio-based nanocarrier using self-assembled, castor oil-derived waterborne polyurethane (WPU) to encapsulate Beauveria bassiana conidia. The resulting WPU nanodispersion (∼34.8 nm) formed a stable coating on the conidial surface through interfacial self-assembly. Encapsulation significantly improved conidial germination and fungal development while enhancing tolerance to ultraviolet irradiation, thermal stress, and chemical stress. Maize phylloplane assays showed that the WPU matrix acted as an adhesion-promoting coating, substantially increasing rainfastness and environmental persistence. Functional assays and microscopic observations indicated reduced hemocyte recognition and phagocytic clearance of WPU-coated conidia, suggesting attenuated early immune elimination during infection. Comparative transcriptomic analysis of encapsulated and unencapsulated conidia under basal and UV-stress conditions revealed differential expression of genes associated with DNA repair, antioxidant defense, and cuticle-degrading enzyme activity, indicating stress-related transcriptional changes. Overall, these results suggest that castor oil-based WPU functions both as a protective coating and as a biologically interactive matrix. This study provides mechanistic insight into polymer-mediated enhancement of entomopathogenic fungi and offers a practical framework for developing high-performance, environmentally stable mycoinsecticide formulations. Download: Download high-res image (337KB) Download: Download full-size image