QTLS FOR A COMPONENT OF PARTIAL RESISTANCE TO CUCUMBER MOSAIC-VIRUS IN PEPPER - RESTRICTION OF VIRUS INSTALLATION IN HOST-CELLS

Ninety four doubled-haploid (DH) lines obtained from the F-1 between P erennial, a cucumber mosaic virus (CMV)-partially resistant Capsicum a nnuum line, and Yolo Wonder, a CMV-susceptible C. annuum line, were an alysed with 138 markers including mostly RFLPs and RAPDs. Clustering o f RAPD markers was observed on five linkage groups of the intraspecifi c linkage map. These clusters could correspond to the centromeric regi ons of pepper chromosomes. The same progenies were evaluated for restr iction of CMV installation in pepper cells in order to map quantitativ e trait loci (QTLs) controlling CMV resistance. This component of part ial resistance to CMV was quantitatively assessed using a CMV strain t hat induced necrotic local lesions on the inoculated leaves. The numbe r of local lesions gave an estimation of the density of the virus-infe ction sites. Genotypic variance among the DH lines was highly signific ant for the number of local lesions, and heritability was estimated to be 0.94. Using both analysis of variance and non-parametric tests, th ree genomic regions significantly affecting CMV resistance were detect ed on chromosomes Noir, Pourpre and linkage group 3, together explaini ng 57% of the phenotypic variation. A digenic epistasis between one lo cus that controlled significant trait variation and a second locus tha t by itself had no demonstrable effect on the trait was found to have an effect on CMV resistance. For each QTL, the allele from Perennial w as associated with an increased resistance. Implications of QTL mappin g in marker-based breeding for CMV resistance are discussed.