engleski

Mapping of quantitative trait loci controlling broomrape (Orobanche crenata Forsk.) resistance in faba bean (Vicia faba L.)

Broomrape (Orobanche crenata Forsk.) can cause considerable losses of faba bean (Vicia faba L.) crop and has become a limiting factor for faba bean production in Mediterranean region. Faba bean breeding programs for broomrape resistance rely primarily on field evaluations where natural parasite populations occur and homogeneity of soil amount of seeds is difficult to reach. 196 F2 plants derived from the cross between susceptible and resistant parent were used as the mapping population. RAPD analysis was carried out using plant tissue from individual F2 plants. F2-derived F3 lines were checked for broomrape resistance in field conditions. The linkage map was constructed by MAPMAKER V2.0 using a LOD score of 3.0 as the threshold for considering significant linkage. One-hundred and twenty-one of the 130 marker loci segregating in the F2 population could be mapped into 16 linkage groups. Nine out of 16 linkage groups were assigned to their specific chromosomes because a number of markers was common with previous studies which used primary trisomics in order to establish the chromosomal location of markers. Simple Interval Mapping (SIM) and Composite Interval Mapping (CIM) were performed using QTL Cartographer. Markers to be used as cofactors for CIM were selected by Forward-Backward stepwise regression. Number of markers to control for the genetic background in CIM was set to 5 as well as to a maximal number of markers found by FB stepwise regression (19). Composite Interval Mapping using 19 markers as cofactors was clearly the most efficient way of localisation of putative QTLs. Four QTLs for broomrape resistance were detected with a LOD > 3.0. Three out of four detected QTLs had explained individually more than 30 % of the phenotypic variance. This result suggests that broomrape resistance in faba bean can be considered as a polygenic trait with major effects of a few single genes. Nevertheless, final simultaneous fit will be carried out in order to calculate the percentage of the phenotypic variance explained by the model including all detected QTLs as well as co-factors. Partial R2 of each detected QTL will give us a better insight of the effect of individual QTL.

QTL mapping; SIM; CIM; broomrape; Orobanche crenata Forsk.; faba bean; Vicia faba L.; resistance

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