engleski

Identification of quantitative trait loci for Ascochyta fabae Speg. resistance in faba bean (Vicia faba L.)

Ascochyta fabae Speg. is a serious pathogen of faba bean (Vicia faba L.) causing blight. Resistant sources have been identified, but little is known on genetic basis of resistance. Ascochyta resistance is a difficult trait to introgress into new varieties because the screening methods are laborious and the inheritance of resistance is quantitative. The objectives of this study were to use molecular markers to identify quantitative trait loci (QTL) controlling Ascochyta resistance in faba bean, and to characterize the genetic basis of resistance expression. Molecular marker analyses were carried out using plant tissue from 1059 individual F2 plants derived from the cross between susceptible (VF 136) and resistant (29H) line. A map of the Vicia faba genome based on isozymes, RAPDs, seed protein genes and microsatellites was constructed. F2-derived F3 lines were inoculated in growth chamber conditions and evaluated for disease severity considering the percentage of damaged leaf area. 98 out of 128 marker loci were mapped into 18 linkage groups covering 1280 cM of the faba bean genome with an overall average marker interval of 13 cM. Simple Interval Mapping (SIM) and Composite Interval Mapping (CIM) were performed using QTL Cartographer. Composite Interval Mapping using 5 markers as cofactors was clearly the most efficient way to locate putative QTLs. Two putative QTLs (Af1 and Af2) associated with Ascochyta resistance were detected jointly accounting for more than 40 % of total phenotypic variability. Both QTLs displayed partial dominant gene action. Identified QTLs could be used as targets for marker-assisted selection (MAS) and provide an opportunity for accelerating breeding programs.

Vicia faba; Ascochyta fabae; QTLs; disease resistance

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