QTL VALIDATION FOR GRAIN YIELD AND NITROGEN USE EFFICIENCY UNDER DIFFERENT NITROGEN LEVELS IN RICE

Abstract

High yielding rice genotypes with high N use efficiency is very important for agriculture sustainability. The study aimed to validate QTLs linked to grain yield (GY) and Nitrogen Use Efficiency (NUE) related-traits using association analysis and single marker analysis in order to identify marker alleles that are associated with target trait under different nitrogen environments. Fifty five rice genotypes were phenotyped for GY and NUE related traits under four different nitrogen treatments (i.e. 0, 20, 40, and 60 Kg N/Fed, respectively). The fifty five rice genotypes were genotyped using four SSR (RM223, RM246, RM242 and RM72) marker linked to QTLs for GY and NUE. Results showed that different degrees of association between the markers fragments and the different traits under the different N-treatments were found. For RM 223, the obtained two fragments (a1 and a2) showed significant and highly significant association with total dry weight (TDW) and (PL) under all N environments. Regarding RM246 marker, b2 and b3 fragments showed highly significant associations with high R2 values with PNUE, NPR and PL traits under all N-treatments. The b2 fragment showed highly significant association with high R2 values for GY, HI and 1000-GW traits. The RM242 fragments (c1 and c2), showed highly significant association with 1000-G and PL traits with high R2 values across the different N-treatments. Regarding the first fragment (c1), R2 values were ranged between 0.13 and 0.23 for 1000-G trait as well as between 0.13 and 0.18 for PL trait, while with c3 fragment, these values were ranged between 0.108 and 0.19 for 1000-G trait and between 0.26 and 0.36 for PL trait. For RM72 marker d1 fragment showed highly significant associations with 1000-GW, PNUE and NPR traits in the different N-treatments, and the R2 values were ranged between (0.21- 0.31), (0.15- 0.19) and (012-016), respectively. On the other hand there were highly significant association between RM72 d3 fragment and GY, NPR and PL with R2 values were ranged between (0.12-0.18), (0.16-0.19) and (0.15-0.26), respectively. These results will assessed in initiating marker-assisted breeding program for NUE and GY traits under low treatments of nitrogen fertilizers.