Genetics of resistance to Karnal bunt of wheat [Neovossia indica (Mitra) Mundkur]

Abstract

Embryos excised from seeds of six generations (P,. P2, Fl , BC" BC2 and F2) of a wheat cross HD29 x HD2329 were cultured on modified MS medium in petriplates already inoculated with secondary sporidia of Kamal bunt of wheat [Neovossia indica (Mitra) Mundkur]. Significant variation for callusing response (CR) (45.55-76.66%) was observed among generations. Presence or absence of N. indica did not affect callusing response. A clear inhibition zone (IZ) was formed around each of the embryo showing callusing, the diameter of IZ varied significantly among generations. It was maximum (3.70 cm) in HD29, the resistant genotype. N. indica was also cocultured with just initiated calli (from embryos). Fresh weight and dry weight of calli (observed after 30 days), also varied significantly among generations. Generation mean analysis indicated that three-parameter model was inadequate for CR, fresh weight and dry weight. Six-parameter modei showed that in presence of N.indica additive, and additive x dominance effects were significant for CR, however, in absence of N. indica oniy additive effects were significant. Duplicate type of epistasis for fresh weight of calli and dominance and dbminance x dominance effects for dry weight of calli were observed in presence of N. indica. Only additive gene effects were significant for diameter of IZ in both three and six parameter model, therefore, selecteion might be helpful for improving resistance to N. indica.