The wild emmer wheat grain protein content 5B QTL introgressed into bread wheat is associated with tolerance to nitrogen deficiency .

Nitrogen (N) is an essential macronutrient for wheat growth and development, its deficiency negatively affects grain yield and grain protein content (GPC). We describe here the dissection of the high grain protein content (GPC) QTL (QGpc.huj.uh-5B.2) derived from chromosome 5B of tetraploid wild emmer wheat, after its introgression into bread wheat (Ruta) by marker assisted selection. The introgression line (IL99) grown for trait validation under three environments, had 33% higher GPC (p<0.05) compared to Ruta, only under low (LN) at the seedling stage. The pleiotropic effect of the QTL on tolerance to N deficiency was confirmed using a semi-hydroponic system under severe LN (10% N) at the seedlings stage. We further dissected the QTL by fine mapping which enabled to delimit the QTL region from ~ 28.55 Mb to a chromosomal segment of only ~ 1.29 Mb that was shared among 12 LN tolerant near-isogenic lines, and which all had the WEW haplotype. This region included 13 potential candidate genes for LN tolerance, annotated as associated with N-stress response (15-cis-ZETA-CAROTENE ISOMERASE), N transport (UREIDE PERMEASE1 and IMPORTIN SUBUNIT BETA-1), and six involved in stress responses (e.g., ATXR6, HISTONE-LYSINE N-METHYLTRANSFERASE), while two genes were uncharacterized. These candidate genes may improve tolerance to nitrogen deficiency and by extension, high nitrogen use efficiency and GPC in N deficient environments. Our study demonstrates the importance of WEW as a source of novel variation for genes and QTLs useful for a sustainable improvement tolerance to N deficiency in wheat.