Marker-assisted transfer of PinaD1a gene to develop soft grain wheat cultivars

Grain softness has been a major trait of interest in wheat because of its role in producing flour suitable for making high-quality biscuits, cookies, cakes and some other products. In the present study, marker-assisted backcross breeding scheme was deployed to develop advanced wheat lines with soft grains. The Australian soft-grained variety Barham was used as the donor parent to transfer the puroindoline grain softness gene Pina-D1a to the Indian variety, DBW14, which is hard grained and has PinaD1bPinbD1a genes. Foreground selection with allele-specific PCR-based primer for Pina-D1a (positive selection) was used to identify heterozygous BC₁F₁ plants. Background selection with 173 polymorphic SSR primers covering all the 21 chromosomes was also carried out, in the foreground-selected BC₁F₁ plants. BC₁F₂ plants were selected by ascertaining the presence of Pina-D1a (positive selection) and absence of Pina-D1b (negative selection). Using the approach of positive, negative and background selection with molecular markers, 15 BC₁F₂ and 31 BC₂F₁ plants were finally selected. The 15 BC₁F₂ plants were selfed and the 31 BC₂F₁ plants were further backcrossed and selfed to raise BC₃F₁ and BC₂F₂ progenies, respectively. A part of the BC₂F₂ seed of each of the 31 plants was analyzed for grain hardness index (GHI) with single-kernel characterization system. The GHI varied from 12.1 to 37.1 in the seeds borne on the 31 BC₂F₁ plants. The reasons for this variation and further course of action are discussed.