Introgression of sheath blight disease tolerance from the transgenic rice event Pusa Basmati1-CG27 to the variety White Ponni through backcross breeding

Abstract

Sheath blight disease caused by Rhizoctonia solani is a major constraint for rice production. In order to obtain transgenic resistance against sheath blight disease, an indica rice variety Pusa Basmati1 (PB1) was transformed with constitutively express chitinase (chi11) and β-1,3-glucanase (GLU) genes. A single-copy transgenic PB1-CG27 showed a high level of tolerance to R. solani. Here, we report the introgression of sheath blight tolerance from PB1-CG27 into a non-basmati rice variety, White Ponni (WP) through backcross breeding. In each of the four backcross generations, the presence of the transgene was checked by hygromycin phosphotrans-ferase (hph) and βglucuronidase (gus) gene-specific foreground selection markers present in the T-DNA of the PB1-CG27 event. RAPD marker-based background selection was done to choose a BC4F1 plant that was similar to the WP recurrent parent. Morphological characters of the introgressed BC4F4 plants matched those of the recurrent WP parent. RT-PCR and western blot analyses confirmed the constitutive expression of the chi11 and GLU genes in the introgressed homozygous BC4F3 plants. Bioassay with R. solani a high level disease tolerance (43% disease reduction) revealed over the control WP plants.