Performance et stabilite de rendement des genotypes de patate douce dans divers environnements a l'Est du Congo

Eight sweet potato genotypes of different geographic origins were evaluated during the 1995 and 1996 growing seasons to determine their performance and stability over seven representative environments in the highlands of Kivu in eastern Congo. Results of combined analysis of variance showed significant differences between genotypes and environments, and significant effects of genotype by environment (G x E) interactions. The highest yielding genotypes were Yan Shu 1 (16.7 t ha-1), Mulungu 1 (12.2 t ha-1) and Mugande (11.9 t ha-1) while the lowest yielding were Nong Da Hong (8.5 t ha-1) and the local Caroline Lee (8.1 t ha-1). Stability analysis of storage root yield, based on the regression coefficient, allowed the identification of high and stable yielding genotypes. Among the clones evaluated, Yan shu 1 and Mulungu 1 were the most stable and high yielding genotypes across all the seven environments. They were retained for release to sweet potato producers in eastern Congo and would be used as parents in sweet potato breeding programme in Congo. The response of genotypes of different origins to altitudes showed that sweet potato is a low and mid-elevation crop of warm climate. It can be grown in eastern Congo to give appreciable yields in altitudes of up to 1,560 m above which yield of most clones gradually decreases due to cooler temperature at higher altitudes.Huit g\ue9notypes de patate douce d'origine g\ue9ographique diff\ue9rente \ue9taient \ue9valu\ue9s durant les saisons culturales des ann\ue9es 1995 et 1996 pour leur performance et leur stabilit\ue9 de rendement dans sept divers environnements repr\ue9sentatifs du Kivu montagneux \ue0 l'est de la R\ue9publique D\ue9mocratique du Congo. Les g\ue9notypes les plus productifs \ue9taient Yan Shu 1 (16,7 t ha-1), Mulungu 1 (12,2 t ha-1) et Mugande (11,9 t ha-1). Les rendements les plus faibles \ue9taient produits par le clone Nong Da Hong (8,5 t ha-1) et la vari\ue9t\ue9 locale Caroline Lee (8,1 t ha-1). Les r\ue9sultats obtenus de l'analyse de la variance combin\ue9e ont montr\ue9 des diff\ue9rences significatives entre les g\ue9notypes, les environnements et les effets d'interaction entre g\ue9notype et environnement (G x E) en ce qui concerne le rendement en tubercules. L'analyse de la stabilit\ue9 du rendement bas\ue9e sur le coefficient de r\ue9gression a permis d'identifier deux g\ue9notypes stables et \ue0 haut rendement \ue0 travers les sept environnements. Ces g\ue9notypes, Yan Shu 1 et Mulungu 1, ont \ue9t\ue9 ainsi s\ue9lectionn\ue9s par les chercheurs pour diffusion aupr\ue8s des producteurs de patate douce \ue0 l'est du Congo. Ils pourront aussi \ueatre utilis\ue9s comme parents dans un programme d'am\ue9lioration de la patate douce au Congo. Le comportement des g\ue9notypes \ue0 travers les altitudes a confirm\ue9 que la patate douce est une culture des basses et moyennes altitudes dans les zones \ue0 climat chaud. Elle a donn\ue9, \ue0 l'est du Congo, un rendement acceptable jusqu'\ue0 1.560 m d'altitude au-dessus de laquelle les rendements baissent graduellement pour la plupart des clones \ue0 cause des faibles temp\ue9ratures entra\ueenant un climat frais d'altitude