Mangat, G.S.Raghavendra N R2018-05-252018-05-252018http://krishikosh.egranth.ac.in/handle/1/5810047658The Punjab Agricultural University, Ludhiana during Kharif 2013 released PR121, a high yielding, bacterial blight (Xa4+xa13+Xa21) resistant rice variety of indica rice. Due to short duration, high yield, less biomass and excellent milling characteristics, PR 121 became the most popular variety among the farmers and millers in the state and occupied more than 7.0 lakh hectares area during Kharif 2017. However it is susceptible to brown plant hopper (BPH). In view of increasing incidence of BPH and depleting water resources, the present study aimed at pyramiding QTLs (qDTY1.1 and qDTY3.1) for grain yield under water stress and genes (Bph20 and Bph21) for BPH resistance into this popular variety through marker assisted backcross breeding (MAS). Introgression line IR96321-1447-561-B-1 (from Apo and Nagina 22) and Oryza minuta alien introgression line IR71033-121-15-B, were used as donors for drought and BPH tolerance respectively. Marker assisted foreground selection was carried out using the SSR markers RM3825, RM5794 and RM520, RM16030 linked to the drought QTLs and RM8231, RM16556 and RM28561, RM28571 linked to BPH resistance. A set of 59 BC1F3 progenies carrying different combinations of drought QTLs/BPH genes along with parents were evaluated under reproductive stage drought stress in rain-out shelter and non-stress conditions for various agro morphological traits. In general, days to 50% flowering were delayed and plant height was reduced under stress conditions. Four lines homozygous for both the drought QTLs yielded at par with recurrent parent under stress conditions. One of the BC1F3 line viz., PAU 7182-1645 possessing both drought QTLs had higher yield potential than PR 121 under non-stress and stress conditions. However, it was comparable with the donor parent under stress conditions. Lines with either of the two QTLs did not show any yield advantage under stress over PR121. The BPH resistance of lines with Bph20 and Bph21 was not comparable to the donor parent. The disagreement between marker genotypes and the phenotypic evaluation could probably be due to incomplete linkage between the selected markers and the target genes or due to the effect of genetic background. The lines carrying different combinations of QTLs/genes can be useful as improved genetic stocks of rice, especially to develop cultivars for the future.ennullThesis