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 β-
glucuronidase (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.