Rht8 gene as an alternate dwarfing gene in elite Indian spring wheat cultivars

Optimizing wheat height to maximize yield has been an important aspect which is evident from a successful example of green revolution. Dwarfing genes (Rht) are known for yield gains due to lodging resistance and partitioning of assimilates into ear. The available and commercially exploited sources of dwarfism in Indian spring wheat are Rhtl and Rht2 genes inspite of availability of over 20 dwarfing genes. Rht8 a Gibberellic acid sensitive dwarfing gene is another reduced height gene commercially exploited in some Mediterranean countries. Two F-2 populations segregating for Rhtl and Rht8 genes with each comprising 398 and 379 plants were developed by crossing European winter wheat cultivars Beauchamp and Capitole with Indian spring wheat cultivar PBW 621. Different genotypic combinations for Rhtl and Rht8 genes were selected from these populations through linked molecular markers and selected F-3:4 lines were evaluated for various agronomic traits in a replicated trial. Reduction in plant height with Rht8 and Rhtl averaged 2.86% and 13.3% respectively as compared to the group of lines lacking dwarfing gene. Reduction was spread along all the internodes of wheat culm and reduction was lower as progress towards the lower inter node. Grain number per spike and highest yield was observed in lines carrying only Rhtl gene. Reduction in plant biomass was observed with either of the dwarfing gene. Longest coleoptile length and seedling shoot length averaged 4.4 +/- 0.09 cm and 19.5 +/- 0.48, respectively was observed in lines lacking any of the dwarfing gene. Negligible reduction of 6.75% and 2.84% in coleoptile length and seedling shoot length, respectively was observed in lines carrying only Rht8 gene whereas F-3:4 lines with Rhtl gene showed 21.64% and 23.35% reduction in coleoptile length and seedling shoot length, respectively. Additive effect of genes was observed as double dwarfs showed 43.31% and 43.34% reduction in coleoptile length and seedling shoot length.