Mapping QTL for Fusarium wilt Race 2 partial resistance in pea (Pisum sativum)
With 3 figures and 4 tables ABSTRACT: Fusarium oxysporum f.sp. pisi (Fop) exists in pea production regions worldwide and causes a vascular wilt resulting in significant crop losses. Four races of Fop have been identified, and resistance to each was reportedly conferred by an individual single dominant gene. Fnw confers resistance to Fop race 2, which can be a serious pathogen for both green and dry pea production in the Pacific Northwest region of the United States. The objectives of this research were to (i) place Fnw on the Pisum genetic map, (ii) detect additional genetic factors associated with resistance to race 2 and (iii) identify closely linked markers for use in pea breeding A recombinant inbred line (RIL) population of 187 F7‐derived lines from the cross ‘Shawnee’/‘Bohatyr’ was developed by single‐seed decent. All 187 RILs, the parents and one set of race 2 pea differential entries were inoculated with Fop race 2 under controlled conditions in three experiments, each with two or three replications per entry. Disease reactions were recorded as percentage diseased plants 10–14 days postinoculation or at regular intervals through flowering or early pod fill. Data for progressive wilting over time, typical of Fop race 2, were used to calculate area under disease progress curve (AUDPC) values. Data for percentage diseased plants placed the putative single gene Fnw on Pisum sativum linkage group IV, with LOD scores ranging from 40.0 to 65.6 and minor loci on LG III (LOD 3.97 and 4.60). AUDPC values allowed for the detection of additional QTL on linkage group III with LOD scores of 3.97 and 4.60. The presence of recombinants in the population indicated that complementary genes were contributed by each parent, both of which showed intermediate reaction to Fop race 2. Results of this research provide a basis for marker‐assisted selection of the major Fnw loci in both green and dry pea breeding programmes, but additional research is necessary to fully characterize the complementary gene action governing resistance of the two minor loci identified.
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