L'intérêt de lignées collectées en Haïti pour l'amélioration variétale du haricot grain (Phaseolus vulgaris L)

Résumé - Parmi d'autres légumineuses, les grains secs de haricots (Phaseolus vulgaris) tiennent une grande place dans l'alimentation haïtienne. Les types de haricots cultivés en Haïti sont très variés, mais ont une tendance générale à la précocité et à l'indifférence photopériodique. Les paysans cultivent des mélanges de gros grains produits par des plantes naines et de grains moyens et petits produits par des plantes à croissance indéterminée : économie de l'investissement en semences et assurance de meilleure régularité de récolte. Les principaux types variétaux cultivés en Haïti sont décrits, ainsi que les meilleures lignées qui en ont été tirées. Des croisements simples ou complexes faisant intervenir soit exclusivement des lignées haïtiennes, soit aussi des variétés provenant d'autres pays, ont permis d'obtenir des lignées améliorées, intéressant non seulement Haïti, mais cultivables également en Afrique et dans le Midi de la France.

Abstract - The value of common bean (Phaseolus vulgaris L) lines isolated in Haiti for bean varietal improvement. Dry beans and peas belonging to Phaseolus, Vigna, Cajanus and Lablab spp are an important constituent of the diet in Haiti. Of these, the common bean (Phaseolus vulgaris L) is cultivated on a widespread scale and is the most popular legume. No doubt for historic, sociological and agricultural reasons common beans grown in Haiti are extremely heterogeneous as regards growth habit, seed size and color, but have in common earliness and indifference to photoperiodicity. Haitian farmers grow mixtures of large beans (produced by dwarf plants), and medium-sized or small beans (produced by plants with indeterminate growth) for seed input saving, and to ensure yield regularity. From beans bought in the markets, or from superior plants chosen in the fields several hundred lines were extracted, 50 of which were preserved after severe elimination had been carried out in Guadeloupe (FWI) for powdery mildew susceptibility at the seedling stage or in southern France for summer heat or common mosaic susceptibility. The principal common bean categories grown in Haiti and the best lines found in each category are described: - large kidney-shaped beans (most of them mottled red) produced by dwarf plants (4 lines are described); - large ovoid beans (most of them mottled red) produced by dwarf plants (1 line described); - medium-sized black beans, produced by plants with indeterminate growth (4 lines described); - small-sized beans of various colors, produced by plants with indeterminate growth (4 lines described); - small-sized uniform red beans produced by plants which become climbing under good fertilization (one line described). Crosses were made in order to obtain still better lines for use in Haiti (and other countries), with tolerance to leaf diseases (such as powdery mildew, rust, and Isariopsis, Chaetoseptoria, Cercospora and Entyloma leaf spots), which in Haiti could result in a yield of 1 t/ha instead of 0.5, with 0.30.30 fertilization, but without fungicide sprays. The general objective was to propose to the farmers a "superior mixture" of the best lines. The programs were as follows: large mottled red-kidney-shaped beans; black beans; small pink or red-mottled beans (the best lines obtained, such as "Salagnac 90" for the first program, have been described). A fourth program aimed at obtaining fresh shell-beans for the FWI: red beans, red or red-striated pods (dwarf or climbing lines following the use in various seasons). Most of these breeding programs involved breeding generations alternated between different climates: Haiti/southern France, Haiti/Guadeloupe, or Haiti/southern France/Guadeloupe. As a consequence of the earliness and day-neutral behaviour of the germplasm used, and also possibly the alternated generations system utilized, the lines resulting from these programs show a wide climatic adaptation. Good results were obtained in some parts of Africa (the highlands of Comoro and the Réunion islands; Burkina-Faso), and southern France where most of them are easily grown and have a satisfactory yield.