Further genetic analysis of a major quantitative trait locus controlling root length and related traits in common wheat

Roots are essential for normal growth, development, and reproduction of higher plants. Consequently, improvement of root system architecture and functionality is of fundamental importance in crop improvement. However, the genetic mechanisms controlling root morphology and function are still not well understood, especially in common wheat, which possesses a complex and unsequenced hexaploid genome. Here we report a more detailed genetic analysis of qTaLRO-B1, a major quantitative trait locus (QTL) previously detected to affect root length and related traits in common wheat. A pair of QTL isolines with different qTaLRO-B1 alleles was developed. Line 178B, carrying the longer root allele, was significantly more efficient in taking up phosphate nutrient and biomass accumulation than line 178A, with the shorter root allele. We mapped qTaLRO-B1 to a 0.9-cM interval on common wheat chromosome 2BS with seven sequence-tagged-site (STS) markers developed from the genes conserved between wheat and Brachypodium distachyon. The seven STS markers were collinearly conserved in tetraploid wheat, but they covered a much larger genetic distance (22.8 cM) in the latter species. In conclusion, we have converted qTaLRO-B1 into a major gene that affects common wheat root length in a qualitative manner, and improved understanding of the genetic location of qTaLRO-B1 and the chromosomal segment carrying this important locus. The implications of our data for further study of qTaLRO-B1 are discussed.