Publications des agents du Cirad

Cirad

Designing of direct seeding cropping systems with Northern Cameroonian farmers

Naudin K., Balarabe O., Guibert H., Abou Abba A., Charpentier H.. 2003. In : Producing in harmony with nature. II World Congress on Conservation Agriculture, Iguaçu Falls, Brésil, 11-15 August 2003. Montpellier : Cirad, 1 p.. Congresso Mundial sobre Agricultura Conservacionista. 2, 2003-08-11/2003-08-15, Foz de Iguaçu (Brésil).

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) testing the potential of partial inbreds in breeding, and (v) building a reference genetic map of molecular markers. 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. Morphological characterization and evaluation have been undertaken on more than 700 accessions in Martinique and Brazil, showing wide variation in quantitative and qualitative traits. Ten clones were selected for their particularly good agronomic qualities in Martinique and six promising Brazilian accessions are being tested for large-scale cultivation and consumer acceptance in Brazil. Multivariate analyses of the morphological data have produced consistent results. Characterization and evaluation was hampered by insufficient multiplication and germplasm transfer regulation in Venezuela, where only 30 accessions could be observed. Molecular characterization, based on RFLP observed with nuclear probes and cpDNA PCR-RFLP, has confirmed the proximity of Ananas and Pseudananas, the absence of interspecific barriers in Ananas, and the importance of a geographic component of variation. The phenograms and cladograms resulting from both molecular studies consistently show three major clusters, one from the South, gathering Pseudananas and A. fritzmuelleri, one from the basins of Orinoco and Rio Negro, grouping most of

Mots-clés : semis direct; paillis; mulch vivant; pratique culturale; brachiaria; céréale; gossypium; cameroun

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