Résumé
This project aimed at obtaining knowledge and tools for the development of cultivars resistant to the main diseases in South America, by (i) characterizing and evaluating available genetic resources, (ii) studying the genetic structure of the genera Ananas and Pseudananas, (iii) developing and applying resistance screening techniques for important pests and diseases in the region, (iv) studying the heredity of agronomic traits, and (v) testing the potential of partial inbreds in breeding. In addition, a standard database is being established in collaboration with IPGRI, to promote information and germplasm exchange. The project, which started in 1997 and ended in 2001, has produced an inventory of the germplasm held in the partners' field collections, allowing exchanges and repatriation of lost germplasm. The list of descriptors has been revised. Multivariate analyses of the morphological data have produced consistent results. Molecular characterization, based on RFLP of genomic DNA and PCR-RFLP of cpDNA has confirmed the proximity of Ananas and Pseudananas, the absence of interspecific barriers in Ananas, the importance of a geographic component of variation, and the existence of a higher genetic diversity in the North of South America. Pineapple taxonomy has been revised. Genetic mapping was based on isozyme, RAPD, AFLP and ISSR markers and carried out on a hybrid progeny between A. bracteatus and A. comosus, following the pseudo-testcross approach. It resulted in a first map of 336 and 154 DNA markers distributed in 46 and 31 linkage groups for these two species. New sources of resistance to fusariosis have been identified, some of which show other interesting traits for the Brazilian producers. According to the first inheritance studies, this resistance seems monogenic and dominant, a result still to be confirmed. Self-progenies obtained from the cultivars Perolera, Primavera, and Roxo de Tefé, showed inbreeding depression, but normal segregation for major leaf traits (spininess, color). Subsequent hybridization of the inbreeds restored vigour. (Résumé d'auteur)