Transgenic indica rice variety Pusa Basmati 1 constitutively expressing a rice chitinase gene exhibits enhanced resistance to Rhizoctonia solani

Agrobacterium-mediated transformation of an elite indica rice variety, Puss Basmati 1, was performed using LBA4404 (pSB1, pMKU-RF2) that harbours a rice chitinase gene (chill) under the control of the maize ubiquitin (Ub/1) promoter-intron. Right border (gus) and left border (hph) flanking sequences and the transgene (chill) in the middle of the T-DNA were used as probes in Southern analysis. Out of eleven independent T-0 plants regenerated, three had single copy T-DNA insertions and eight had multiple T-DNA insertions. Nine T-0 plants carried the complete T-DNA with the chitinase transgene. Two T-0 plants did not carry chill, though they had other T-DNA portions. Three plants harbouring single copy insertions and one plant harbouring two inserted copies were analyzed in detail. A segregation ratio of 3:1, reflecting T-DNA insertion at a single locus, was observed in the progeny of all the four T-0 plants. Northern and western blot analyses of T-0 plants revealed constitutive expression of chitinase at high levels. Bioassays of T-0 plants indicated enhanced resistance to the sheath blight pathogen, Rhizoctonia solani, in comparison to control plants. A homozygous transgenic line was established from one T-0 line, which exhibited the maximum resistance to R. solani.