Rice is an important food crop for three billion people worldwide. The crop is vulnerable to several diseases. Sheath blight caused by fungal pathogen Rhizoctonia solani is a significant threat to rice cultivation accounting for up to 50% yield losses. The pathogen penetrates leaf blades and sheaths, leading to plant necrosis; and major disease resistance gene against the pathogen is not available. This study describes development of sheath blight resistant transgenic indica and japonica rice cultivars through introduction of antifungal β-1,3-glucanase transgene cloned from Trichoderma. The transgene integration and expression in transformed T0 rice plants was examined by PCR, RT-PCR, qRT-PCR demonstrating up to 5-fold higher expression as compared to non-transgenic plants. The bioassay of T0, T1 and homozygous T2 progeny plants with virulent R. solani isolate revealed that plants carrying high level of β-1,3-glucanase expression displayed moderately resistant reaction to the pathogen. The optical micrographs of leaf sheath cells from moderately resistant plant after pathogen inoculation displayed presence of a few hyphae with sparse branching; on the contrary, pathogen hyphae in susceptible non-transgenic plant cells were present in abundance with profuse hyphal branching and forming prominent infection cushions. The disease severity in T2 progeny plants was significantly less as compared to non-transgenic plants confirming role of β-1,3-glucanase in imparting resistance.
Keywords: Bioassay; Optical microscopy; Rhizoctonia solani; Sheath blight resistance; Transgenic rice; β-1,3-glucanase.
© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.