Genetic variation in Coffea canephora L. (Var. Robusta) accessions from the founder gene pool evaluated with ISSR and RAPD

Discovered in Congo in 1898, Coffea canefora var. robusta accounts for 25 to 40% of the coffee grown in the world. Most genetic diversity of robusta coffee accessions conserved in ex situ collections hasbeen estimated from morphological characteristics. There are limited studies on genetic variability and diversity in C. robusta. Inter-simple sequence repeat (ISSR) and random amplified polymorphic DNA(RAPD) markers were used to assess the level of genetic variability among robusta coffee accessions from the founder gene pool in the Democratic Republic of Congo (DRC). The present study clearlyestablished the high variability in the Congolese genepool. RAPD primers detected a higher level of polymorphic loci (95%) than ISSR markers (52%). Each accession could be genotyped using RAPDmarkers and both markers were efficient in revealing the genetic variability. Jaccard’s similarity coefficients generated to determine the genetic distances among accessions, revealed that most of theaccessions were genetically distant from each other. The accessions tested represent useful genetic materials for breeding for resistance to tracheomycose and other traits in DRC

Dynamique foliaire et croissance du maïs: Application du modèle «STICS» en conditions tropicales en RD-Congo

Plusieurs modèles de simulation de la croissance foliaire ont été développés, surtout sous climat tempéré. Pour utiliser ces modèles en milieu tropical, une étude, conduite en RD Congo, se propose 1) de caractériser le couvert de 3 variétés de maïs adaptées en conditions locales et 2) d'ajuster le modèle de simulation de l'évolution de l'indice foliaire en fonction du temps thermique. Les observations ont servi à adapter le modèle de croissance de Baret dans le modèle Stick, par estimation des paramètres. La fréquence d'apparition des feuilles de maïs obtenue est une fonction non linéaire et le nombre total de feuilles a été de 14. Il a fallu 1761,5 °C j pour que la variété Mus atteigne la maturité et 1979,5 °C j pour Salongo 2 et la variété locale. Le module de croissance de modèle de culture Stics est applicable en régions tropicales, à condition d'ajuster certains paramètres. Les résultats de simulation ont permis de comparer les variétés investiguées, et d'en déterminer les stades phénologiques. Les variétés génétiquement améliorées ont présenté une courbe de croissance plus élevée que la locale. Les variétés ayant un indice foliaire (LAI) plus grand ont eu également un rendement en biomasse sèche et en grain plus élevé.Several simulation models for leaf development and plant growth have been developed for temperate climate conditions. The main objectives of the present study are 1) to characterize the canopy of 3 corn varieties adapted to local tropical conditions in DR - Congo ; 2) to develop a simulation model for leaf area index as a function of thermal time. Data, obtained from field experiments on corn, were used to calibrate Baret plant growth model (in Stics simulation Model). Leaf appearance was a non-linear function of thermal time and the average total leaf number per plant for the 3 varieties was 14. Mus variety required 1761.5 °C days (growing degree day) to complete its developmental cycle. This value was 1979.5 °C days for the local and the Salongo 2 varieties. The initial simulation model has been modified and adapted to the studied conditions. Overall, the collected data were useful for a reliable analysis of the phenology of the three varieties. Genetically improved varieties showed growing patterns with higher coordinate values than local varieties. Moreover, larger leaf area indices (LAI) were associated with higher dry biomass weights and grain yields.Keywords: Simulation, leaf Area Index, STICS model, Corn, DR-Cong

Participatory variety selection and characterization of Sorghum bicolor L. (Moench) elite accessories from Malawi gene pool

No Abstract.International Journal of Tropical Agriculture and Food Systems Vol. 2 (1) 2008: pp. 7-1