Mappaggio fine di un QTL principale per la resa in granella sul cromosoma 3B di frumento duro

In durum wheat, two major QTL for grain yield (Qyld.idw-2B and Qyld.idw-3B) and related traits were identified in a recombinant population derived from Kofa and Svevo (Maccaferri et al. 2008). To further investigate the genetic and physiological basis of allelic variation for this important trait, the fine mapping of Qyld.idw-2B e Qyld.idw-3B was done during the PhD. In this regard, new molecular markers were added to increase the map resolution in the target interval. For Qyld.idw-2B region COS markers derived from the synteny between wheat and rice/ sorghum /brachypodiu genomes were screened. While for Qyld.idw-3B region SSR, ISBP and COS markers obtained from BAC end-sequences and BAC sequences generated during the construction of the 3B physical map (Paux et al., 2008) were screened. In the RIL population a final map resolution of 2,8 markers/cM for Qyld.idw-2B and 0,6 markers/cM for Qyld.idw-3B were obtained. Eighteen pairs of near-isogenic lines (NILs) for Qyld.idw-3B were obtained from F4:5 heterogeneous inbred families. In order to confirm the phenotypic effect of the QTL all pairs were evaluated in field trials (2010 and 2011) for all traits. Three pairs of NILs, with contrasted haplotypes at the target region, were crossed to produce a large F2 population (ca. 7,500 plants in total) that was screened for the identification of recombinants. A total of 233 homozygous F4:5 segmental isolines were obtained and the phenotypic and genotypic characterization of these materials were done. A fine mapping for Qyld.idw-3B was obtained and the QTL peak was identified in a interval of 0,4 cM. All markers were anchored to the Chinese Spring physical map of chr. 3B, which allowed us to identify the BAC Contigs spanning the QTL region and to assign the QTL peak to Contig 954. Sequencing of this contig has revealed the presence of 42 genes.