Abstract only

Durum wheat (Triticum durum Desf.) is a main cereal crop for the Mediterranean area, including Southern Europe, West Asia and North Africa (WANA). Durum wheat is also important in Mexico and South-Western USA, Northern-USA and Canada, Central and East Europe, Australia and other countries. Therein, main objectives of durum wheat breeding are adaptation (fine tuning of plant development, heading date and maturity) to the local environmental conditions and improved response to the main cereal diseases. Therefore, UNIBO and Produttori Sementi Bologna (PSB), in collaboration with CIMMYT and molecular plant pathologists, developed a program for mapping useful genetic variation through a joint linkage and association mapping approach targeted to heading date across environments and resistance to durum diseases. Four recombinant inbred line mapping populations based on diverse parents (Kofa × Svevo, Meridiano × Claudio, Colosseo × Lloyd and Simeto × Levante) each including ca. 180 RILs and a germplasm panel of 270 accessions from world-wide have been genome-wide characterized with SSR, DArT and the recently developed wheat Illumina 90k SNP array. Phenotyping for heading date as well as for disease resistance in artificially inoculated field trials was carried out through a series of projects and collaborations. As to heading date control, the major QTLs with the corresponding allelic variants present in the germplasm were identified and described in terms of their allelic effect and molecular haplotypes. The QTLs were found to correspond to major PPD and VRN genes, with effects associated to both A- and B-genome homeologous copies whose allelic variants have been sequenced, as well as to earliness-per-se QTLs. The investigation of response to durum wheat diseases allowed to deeply characterize: Lr14a, a major gene for leaf rust resistance on chr. 7BL (Colosseo × Lloyd), a major QTL for resistance to Soil-Borne Wheat Mosaic Virus (QSbm.ubo-2B), two major QTLs for the powdery mildew infection response (Meridiano × Claudio and Simeto × Levante) on chr. 6BL and 7BL (QPm.ubo-6B and QPm.ubo-7B and QTLs associated to Septoria tritici blotch infection response. Association mapping with the germplasm panel has been used to validate the major QTLs and to investigate the distribution of the main contrasting haplotypes at each locus. Fine mapping of the major genes/QTLs identified from this mapping effort has been initiated with the aims of developing markers tightly linked to the genes/QTLs and step toward positional cloning. For Lr14a and QSbm.ubo-2B, the synteny conservation provided the bases for SNP development based on the wheat, rice and Brachypodium horthologs. Fluorescence-based assays such as Kaspar and High Resolution Melting analysis suitable for high-throughput marker assisted selection (MAS) were developed. Profiling all of the mapping materials with the wheat Illumina 90k SNP array provided a considerable enrichment of the QTL regions with SNPs associated to coding sequences, allowing to further characterize the functional haplotypes, to characterize the local linkage disequilibrium extent and to provide more markers for MAS. An overview of the results will be presented.

Global Wheat Program

English

Lucia Segura

INT2585

CIMMYT Staff Publications Collection