An integrated molecular linkage map of pepper (Capsicum annuum L.), including mainly RFLP and RAPD markers, has been constructed by alignment of three intraspecific linkage maps generated by segregating doubled-haploid progenies. A total of 85 markers covered approximately 820 cM in 14 linkage groups. Four linkage groups were assigned to 4 chromosomes. Two new genes of agronomic interest were located: L controlling hypersensitive resistance to TMV and up controlling the erect habit of the fruits. The C gene controlling the fruit pungency was more precisely located. This map is estimated to represent from 36 to 59% of the total pepper genome. An examination of segregation data has revealed several genomic regions with aberrant segregation ratios often favouring the agronomic big-fruited parents, particularly in crosses involving the exotic parent CM334, suggesting that these genome regions are subjected to selection during the process of doubled-haploid production. The suitability of doubled-haploid progenies for mapping projects and the differences observed between this intraspecific integrated map with earlier published interspecific pepper maps are discussed.

Cet article décrit les améliorations de la technique de culture in vitro d'anthères de piment (Capsicum annuum L.) qui permettent l'obtention de plantes haploïdes et diploïdes à des fréquences élevées quel que soit le génotype de la plante d'origine. Les principaux facteurs de réussite sont :le passage à + 35 °C et à l'obscurité pendant les 8 premiers jours de culture sur un milieu gélosé contenant soit de la kinétine à 10-' et du 2-4 D à 10-', soit de la kinétine à 2 x 10-1 et du 2-4 D à 10-'. La première combinaison de substances de croissance semble supérieure.-Le repiquage des anthères, après 12 jours de culture, sur un nouveau milieu ne contenant que de la kinétine à 10-' (= Rl). Des plantes sont obtenues directement sur RI après environ 40 jours de culture. Cependant, un pourcentage plus élevé d'embryons donne naissance à des plantes si on les repique sur un milieu enrichi en kinétine (2 x 10-") (= R2). Cette technique a permis d'obtenir de 5 à 40 plantes pour 100 anthères mises en culture à partir de cultivars à gros fruits, de F, entre cultivars de type poivron ou de F, entre cultivars à gros et à petits fruits. Parmi les plantes obtenues, on peut noter une fréquence parfois très élevée (jusqu'à 50 p. 100) de plantes diploïdes. Certaines d'entre elles apparaissent sous forme de chimères haplo-diploïdes.

A molecular map of pepper (Capsicum sp.) totalling 720 cM has been constructed in an interspecific F2 cross with restriction fragment length polymorphisms and isozymes. Nineteen linkage groups were formed from 192 molecular markers. Twenty-six markers showed no linkage to any others. Twenty-eight markers showed significant deviation from expected Mendelian ratios and clustered in the genome. Two quantitative trait loci controlling the number of flowers per node were mapped to linkage group 10. The order of markers in at least 228 cM (31.7%) of the pepper genome is conserved with respect to the tomato genome, with a minimum of 15 chromosome breakage events postulated to have occurred since their divergence from a common ancestor. Comparisons of meiotic recombination in 14 conserved intervals indicates that tomato has a higher rate of recombination than does pepper in the crosses studied. Evidence suggests that centric fusions and resulting chromosome breakage events are mechanisms for genome evolution in the Solanaceae.

Genetic analysis of resistance to PVY in androgenetic doubled haploid lines, Fl, F2 and backcross progenies of the Mexican pepper line, CM 334 (Capsicum annuum L.), was performed . Three reaction types were observed when seedlings were inoculated with several PVY strains of different pathotypes and with an American PeMV strain . Resistant genotypes never showed systemic symptoms although some individuals sporadically developed necrotic local lesions on inoculated cotyledons . Susceptible genotypes exhibited either a typical systemic mosaic or a systemic necrosis that caused the death of the inoculated seedlings . Segregation analyses indicated that resistance to pepper potyviruses in CM 334 is conferred by two genes . The first one, tentatively named Pr4, is dominant and confers the resistance to all now known pathotypes of PVY and to PeMV The second one, tentatively named pry, is recessive ; it confers only the resistance to common strains of PVY The systemic necrotic response is conferred by an independent dominant gene, tentatively named Pnl . 231

Immunofluorescence microscopy, azur A staining of viral inclusion bodies, and ELISA tests revealed differences between resistant and susceptible decapitated plants of pepper for virus distribution through the plant but not for virus multiplication and spread in the artificially inoculated leaves. Within 7 to 10 days after inoculation, viral antigens were detected with ELISA tests in all organs of the susceptible plants; only in inoculated leaves of highly resistant plants; and in inoculated leaves, primary stems, and primary roots of partially resistant plants. Immunofluorescence microscopy revealed that infection in petioles, stems, and roots of resistant varieties was restricted to one or two phloem bundles and did not spread to neighbouring tissues or to other plant organs. However, in some partially resistant plants the virus spread lately to other tissues and organs, resulting in a delayed systemic infection and mosaic symptoms on one or two axillary shoots.