Progress in the Fine Mapping of QYLD.IDW-3B, a Major Grain Yield QTL 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. The fine mapping of QYld.idw-3B was performed within the FP7-funded TriticeaeGenome project. 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. To confirm the effect of the QTL on plant height, peduncle length, grain yield and related traits, a replicated field experiment was carried out in 2012 with the 61 most informative segmental isolines. 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 in the target region. The functional characterization of these genes is underway by expression analysis. Additionally, to confirm and/or identify new candidate genes for Qld.idw-3B the BAC library of Triticum turgidum LDN65 (Cenci et al. 2004, Genome 47: 911–917), characterized by a haplotype in the target region similar to cv. Kofa, was screened. The BAC clones identified are being sequenced.