|Saturation of genomic regions conferring broomrape and ascochyta blight resistance in faba bean (Vicia faba L.).
Gloria María García1, Ana María Torres1, Zlatko Šatović2, Belén Román1, Ramón Díaz3
1Centro 'Alameda del Obispo' - IFAPA, Área de Mejora y Biotecnología, Córdoba, Spain
2University of Zagreb, Faculty of Agriculture, Svetošimunska cesta 25, 10000 Zagreb, Croatia,
3Colegio de Postgraduados - Campus Puebla, C.P. 72760, Puebla, Pue., Mexico
Broomrape (Orobanche crenata Forsk.) and ascochyta blight (caused by Ascochyta fabae Speg.) resistance in faba bean (Vicia faba L.) are complex traits, difficult to manipulate using conventional breeding procedures. The accurate identification of genomic locations of individual quantitative trait loci (QTLs) controlling resistance is of utmost importance in order to develop marker-assisted selection (MAS) programmes. Previous QTL mapping studies in F2 as well as in recombinant inbred lines (RIL) population detected two QTLs controlling broomrape resistance that were stable across generations and across environments: Oc2 (linkage group VI.B) and Oc3 (LG II.A). Similarly, two QTLs conferring resistance to Ascochyta fabae were identified in F2 population and further validated in RILs: Af1 (LG III.A) and Af2 (LG II.A).
Bulked segregant analysis (BSA) based on previous QTL mapping information was applied to saturate the targeted regions. Bulks fixed for alleles of the two markers flanking four QTL regions were selected from the RIL population. More than seven hundred RAPD primers were screened for polymorphism between the two bulks of each target region revealing 31 putatively linked markers. Twenty-four out of 31 RAPD markers were mapped to target linkage groups: 11 to LG VI.B (Oc2), 8 to LG II.A (Oc3 and Af2), and 5 to LG III.A (Af1). By inclusion of additional markers the average intermarker distance on target linkage groups significantly decreased allowing more accurate determination of QTL locations and effects.
Key words: Resistance breeding, Quantiative trait loci (QTLs), Bulk segregant analysis (BSA), Saturation mapping