No abstract

Phosphorus (P) is one of the macro nutrients essential for plant growth and development. Rice (Oryza sativa L.) is sensitive to P starvation and its deficiency influences many key plant functions which results in crop yield penalty.Although the hybrid rice segment is well-known for its yield heterosis, P deficiency and bacterial leaf blight (BLB) diseases are the evident limitations. APMS6B, the female parent of DRRH-3 is susceptible to low P and bacterial blight disease. In the present study, the improvement of APMS6B to P starvation and resistance to bacterial leaf blight (BB) was carried out using marker-assisted backcross breeding (MABB) approach. Kasalath (+ Pup1 QTL) was used as donor and a promising IL (ATR 594-1) at BC1F4 generation was identified with 81.15% RPGR.Concurrently, this IL was intercrossed with GU-2 (+ Xa21 and Xa38). Hybridity of Intercross F1s (ICF1) was confirmed through foreground selection having maximum RPGR (88.29%) and were selfed to produce ICF2. The resultant progenies were phenotyped for BB using Xoo inoculum (IX-020), simultaneously genotyped with gene specific functional SSR markers for Xa21 and Xa38. The identified BB resistant plants were subjected to foreground selection for Pup1. Four promising ICF3 plants (BP-10-1, BP-10-3, BP-10-5 and BP-10-15 with Xa21, Xa38 and Pup1) along with parents and checks were screened both in low P plot (<2 kg P2O5 ha -1 ) as well as in normal plot (>25 kg P2O5 ha -1 ) during dry and wet seasons 2018. Based on the field evaluation, four promising intercrossed lines were identified with better root architecture in terms of root length and root volume. In addition, less % reduction in grain yield (39.10%) under P starvation and less susceptibility indices values (<1) for BB were observed. These lines may be utilized in the CMS conversion programme and development of climate resilient, biotic and abiotic tolerant rice hybrids.