Dissection of Quantitative Trait Loci (QTL) for Root Characters in Synopdh Bi-Parental Mapping Population.

Research aimed at elucidating traits contributing to drought tolerance requires an understanding of plant physiology and the complex network of stress responses. The root system of plants is a major component that has a significant role in stress response. The genetics of the root system is still not dissected for crops such as wheat and this lack of knowledge prohibits the use of marker assisted selection. The Synthetic W7984*Opata-M85 bi-parental double-haploid mapping population (SynOpDH) is the reconstructed version of a well-known International Triticeae Mapping Initiative (ITMI) population. ‘Opata-M85’ is a CIMMYT bread wheat cultivar and the 'Synthetic W7984' wheat is an amphiploid generated from a cross between Aegilops tauschii (D genome donor of bread wheat) and ‘Altar-84’, a Mexican durum wheat cultivar. Experiments were replicated over two growing seasons where the parents and 150 progeny were grown in 10 cm diameter by 1 m long PVC tubes until maturity. Plants were harvested, root and shoot biomass traits were measured, and phenotypic data were analyzed. There was genotypic variation between the 150 lines. Two previously published and publicly available genetic maps were used for linkage and QTL mapping. Two major QTLs for total root biomass were detected on homoeologous chromosomes 2A and 2D with LOD scores of 10.9 and 20.8 respectively. The phenotypic effects of these two QTL were 17.74% and 40.04%, respectively. There was close linkage between these QTLs and photoperiod sensitivity genes, Ppd-D1 and Ppd-A1. A second set of experiments to validate the interaction between root biomass QTLs and Ppd genes was conducted. Six pairs of genotypes with maximum similarity, except contrasting markers of QTL for root biomass, were evaluated in pots under 18 h day light until heading. Effect of Ppd genes were effectively blocked, and genotypes with Synthetic W7984 allele had significantly higher mean values for root biomass when compared to lines with Opata M85 allele. These results suggest that two major QTLs are persistent with or without the effect of Ppd genes.