Marker assisted improvement of low soil phosphorus tolerance in the bacterial blight resistant, fine-grain type rice variety, Improved Samba Mahsuri

Improved-Samba-Mahsuri (ISM), a high-yielding, popular bacterial blight resistant (possessing Xa21, xa13, and xa5), fine-grain type, low glycemic index rice variety is highly sensitive to low soil phosphorus (P). We have deployed marker-assisted backcross breeding (MABB) approach for targeted transfer of *Pup1*, a major QTL associated with low soil P tolerance, using Swarna as a donor. A new co-dominant marker, K20-1-1, which is specific for *Pup1* was designed and used for foreground selection along with functional markers specific for the bacterial blight resistance genes, Xa21, xa13, and xa5. A set of 66 polymorphic SSR marker were used for the background selection along with a pair of flanking markers for the recombination selection in backcross derived progenies and in BC₂F₂ generation, 12 plants, which are homozygous for *Pup1*, all the three bacterial blight resistance genes and possessing agro-morphological traits equivalent to or better than ISM were selected and selfed to produce BC₂F₃s. They were evaluated in plots with low soil P and normal soil P at ICAR-IIRR, Hyderabad for their low soil P tolerance, and bacterial blight resistance and superior lines were advanced to BC₂F₆. One of the lines, when tested at multiple locations in India was found promising under both normal as well as low soil P conditions.

H. K. Mahadeva Swamy, M. Anila, R. R. Kale, G. Rekha, V. P. Bhadana, M. S. Anantha, P. Brajendra, C. H. Balachiranjeevi, S. K. Hajira, B. Laxmi Prasanna, K. Pranathi, T. Dilip, M. B. V. N. Kousik, G. Harika, K. Surekha, R. Mahender Kumar, C. Cheralu, V. Gouri Shankar, G. S. Laha, M. S. Prasad, L. V. Subba Rao, M. S. Madhav, S. M. Balachandran, R. M. Sundaram