Characterization and Fine Mapping Of QYld.idw-3B, A Major QTL For Grain Yield In Durum Wheat

A major QTL (QYld.idw-3B) for grain yield was detected on the chromosome 3BS in a mapping population (Kofa x Svevo) of durum wheat (Maccaferri et al. 2008, Genetics 178:489-511). QYld.idw-3B influences also other important agronomic traits such as plant height, peduncle length, leaf greenness and thousand kernel weight. To further investigate the genetic and physiological basis of this QTL, the fine mapping of QYld.idw-3B was performed within the FP7-funded TriticeaeGenome project. A total of 19 NIL pairs were phenotypically characterized in 2010 and 2011. In both years, the effect of the QTL was confirmed for all target traits. Three NIL pairs were crossed to obtain a large mapping population of 7,500 F₂ that were screened to identify recombinants within the QTL interval. In 2011, 233 F₄ segmental isolines were phenotypically characterized for plant height and peduncle length, two main traits influenced by QYld.idw-3B. In order to further characterize the effect of the QTL, a replicated field experiment was carried out in 2012 with the 61 most informative segmental isolines. Besides the main agronomic traits and grain yield, leaf greenness and water-soluble carbohydrates were also investigated.  The results confirm the co-localization of all traits in the same region of 0.22 cM. All markers added in the region were anchored to the physical map of chr. 3B of cv Chinese Spring (Paux et al. 2011, Science 322:101-104) and this allowed us to identify the most likely candidate genes. The functional characterization of these genes is underway by expression analysis by RT-qPCR.