Inheritance of partial resistance against Colletotrichum lindemuthianum inPhaseolus vulgaris and co-localization of quantitative trait loci with genes involved in specific resistance

Anthracnose, one of the most important diseases of common bean (Phaseolus v ulgaris), is caused by the fungus Colletotrichum lindemuthianum, A "candida te gene" approach was used to map anthracnose resistance quantitative trait loci (QTL), Candidate genes included genes for both pathogen recognition ( resistance genes and resistance gene analogs [RGAs]) and general plant defe nse (defense response genes). Two strains of C, lindemuthianum, identified in a world collection of 177 strains, displayed a reproducible and differen tial aggressiveness toward BAT93 and JaloEEP558, two parental lines of I! v ulgaris representing the two major gene pools of this crop. A reliable test was developed to score partial resistance in aerial organs of the plant (s tem, leaf, petiole) under controlled growth chamber conditions. BAT93 was m ore resistant than JaloEEP558 regardless of the organ or strain tested. Wit h a recombinant inbred line (RIL) population derived from a cross between t hese two parental lines, 10 QTL were located on a genetic map harboring 143 markers, including known defense response genes, anthracnose-specific resi stance genes, and RGAs, Eight of the QTL displayed isolate specificity. Two were co-localized with known defense genes (phenylalanine ammonia-lyase an d hydroxyproline-rich glycoprotein) and three with anthracnose-specific res istance genes and/or RGAs, Interestingly, two QTL, with different allelic c ontribution, mapped on linkage group B4 in a 5.0 cM interval containing And ean and Mesoamerican specific resistance genes against C, lindemuthianum an d 11 polymorphic fragments revealed with a RGA probe. The possible relation ship between genes underlying specific and partial resistance is discussed.