Diversit{é} g{é}n{é}tique des vari{é}t{é}s de NERICAs et des vari{é}t{é}s « intersp{é}cifiques » (Oryza glaberrima x O. sativa) de bas-fonds et {é}tude du d{é}terminisme g{é}n{é}tique de la comp{é}titivit{é} des vari{é}t{é}s de riz vis – {à} – vis des mau uri icon

abstract

  • Rice is a major staple food for Sub-Saharan African population. The creation of the new rice varieties: New Rice for Africa (NERICA) has increased rice production in Sub Saharan Africa. Theses varieties combine the potential of their two parents and are also cultivated in different cropping systems. The current research studies lowland NERICAs and « promising lines » genetic diversity and genetic determinism of rice weed competitiveness. The agromorphological characterization used experimental design an augmented randomized complete block, 23 agro-morphological traits were collected and during two consecutive seasons at Ouedémé. On the other hand, 74 (SHAWHON/WAB56-50) and 120 (TOGIR64/IR64) SSR markers was used to evaluate the proportion of African parental genomic contribution to plant material. The screening of fourteen parental using a split plot design with 3 weeding regimes (0, 1 and 4 weeding), 3 types of the traits and genetic analysis from F1, F2, BC1F1 and BC2F1 population was realized to understand the genetic determinism rice weed competitiveness. Tillering at 60 days after sowing (DAS), plant height at maturity, maturity and spikelet fertility were the most discriminate and could therefore supplement a wide range of variables for phenotypic diversity study. Lowland NERICAs and promising lines varieties were grouped in cluster 1 containing the desired characters adapted to lowland rice cultivation and the entries were grouped into three clusters irrespective of the level of backcrossing of genotypes. The estimated average O. glaberrima genome coverage was 11% (BC2), 6.07% (BC3) and 7.55% (BC4) and the highest proportion of O. glaberrima genome was observed on Chromosomes 2 (BC2), 6 (BC3) and 12 (BC4). An introgression rate of 15.31% was observed in promising lines. The determination of broad sense heritability showed three types of heritable traits and the dominant weed species were Acanthospermum hispidum, Dactyloctenium aegyptium and Digitaria horizontalis. The variety CG20 of the African species was selected as the most competitive variety. The statistical model used has revealed that the dominant effects are higher than additive effects except for the high in the crosses. Additionally, high xiv These de Doctorat de l’Universite d’Abomey-Calavi Spécialité : Ressources Phytogénétiques et Protection des Cultures additive variances and broad sense heritability were obtained from CG20 x FKR19 cross. These results represent the interesting research perspectives for a better management of genetic diversity of plant material studied and a better understanding of genetic determinism of rice weed competitiveness and answering consumer’s expectation.

publication date

  • 2012