Inheritance of Partial Resistance AgainstColletotrichum lindemuthianuminPhaseolus vulgarisand Co-localization of Quantitative Trait Loci with Genes Involved in Specific Resistance

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Abstract
Anthracnose, one of the most important diseases of com- mon bean (Phaseolus vulgaris), is caused by the fungus Colletotrichum lindemuthianum. A "candidate gene" ap- proach was used to map anthracnose resistance quantita- tive trait loci (QTL). Candidate genes included genes for both pathogen recognition (resistance genes and resistance gene analogs (RGAs)) and general plant defense (defense response genes). Two strains of C. lindemuthianum, identi- fied in a world collection of 177 strains, displayed a repro- ducible and differential aggressiveness toward BAT93 and JaloEEP558, two parental lines of P. vulgaris representing the two major gene pools of this crop. A reliable test was developed to score partial resistance in aerial organs of the plant (stem, leaf, petiole) under controlled growth cham- ber conditions. BAT93 was more resistant than Jalo- EEP558 regardless of the organ or strain tested. With a recombinant inbred line (RIL) population derived from a cross between these two parental lines, 10 QTL were lo- cated on a genetic map harboring 143 markers, including known defense response genes, anthracnose-specific resis- tance genes, and RGAs. Eight of the QTL displayed isolate specificity. Two were co-localized with known defense genes (phenylalanine ammonia-lyase and hydroxyproline- rich glycoprotein) and three with anthracnose-specific re- sistance genes and/or RGAs. Interestingly, two QTL, with different allelic contribution, mapped on linkage group B4 in a 5.0 cM interval containing Andean and Mesoamerican specific resistance genes against C. lindemuthianum and 11 polymorphic fragments revealed with a RGA probe. The possible relationship between genes underlying specific and partial resistance is discussed.