Comparative QTL mapping of morpho-phenological traits related to weed competitive ability in two bi-parental populations of wheat (Triticum aestivum L.)

Plant height, heading date, juvenile growth habit, and tiller number are important traits for increasing wheat yield potentials under future climate change. In the current study, these morpho-phenological traits were investigated in the same bi-parental population at early (F2-derived) and late (F6:7) stages of inbreeding. The aim was to i) evaluate the resolution of genetic maps to detect major/minor quantitative trait loci (QTLs), ii) compare QTLs for the investigated traits, and iii) identify candidate genes underpinning weed competitive ability in wheat (including additive and dominance effect). A total of 176 F2:3 and 178 F6:7 lines generated from crossing Lankaodali and Rebelde were grown in field trials at CREA-CI in Foggia (Italy) and phenotyped during four growing seasons. All samples were also genotyped with an Illumina Infinium 15K wheat SNP array. Positive correlations were observed among all investigated traits. The resulted genetic maps identified 36 and 38 linkage groups, which covered 2,486.78 and 3,732.83 cM in the F2 and RIL, respectively, although a higher marker density was observed in F2 (0.7 cM) rather than in RIL (1 cM). A total of 30 and 19 QTLs were identified in the F2:3 and F6:7, respectively. Some of them were only detected in the F2:3, suggesting their relatedness to the dominance effect. In addition, the genetic effects of the QTLs were smaller in the F6:7 generation for all traits. Remarkable QTLs associated with juvenile growth habit and heading date were founded on chromosomes 1B, 2B, 2D, 5A, and 7D in both F2:3 and F6:7. Interestingly, some of these SNPs were located in coding regions of vernalization requirement (Vrn-1) and reduced height (Rht-1) genes, confirming their importance for controlling wheat adaptative traits. Interestingly, several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In conclusion, this work showed the potential of the F2-derived population for providing the most abundant genetic information to identify major QTLs in bread wheat.