GENETIC IMPROVEMENT OF RICE (Oryza spp.) FOR YIELD AND AROMA IN TOGO
ABSTRACT
In Togo, the quantity of rice produced is very low compared to the needs. Farmers and consumers prefer aromatic rice. With a view to increase the local production and supply farmers with aromatic and higher yielding lines, this research was conducted to lay the foundation of a rice breeding programme in the country. The research investigated farmers’ preferences and production constraints, established a germplasm collection and studied its genetic diversity, characterized the germplasm for yield and aroma, developed aromatic and yielding F1 hybrids and estimated genetic parameters. The methodologies used to achieve the set goals consisted in focus group discussions and questionnaire survey to record information from farmers, the collection of accessions around the country through prospecting survey, the genetic diversity studies (notably principal components and cluster analyses), the phenotypic and genotypic characterization of the germplasm for aroma and yield, as well as crosses of the parents identified and the genetic analysis (notably GXE interactions, combining ability and genetic variance components) of yield and its component traits at four locations. From the participatory rural appraisal, absence of aroma in the new varieties introduced was the main reason for which farmers failed to adopt them. Their major preferences were presence of aroma, yield and earliness. Birds, insects and iron toxicity were their major production constraints. Collected germplasm comprised of 50 accessions were grouped, after diversity study using 30 agro-morphological traits and 5,736 informative SNP markers, in four and five clusters respectively, with 13 distinct samples of IR 841. Three aromatic and six high yielding parents were selected from the characterization, and used respectively as male and female parents to develop 18 F1 progeny families using the North Carolina Design II. The evaluation of the 18 F1s and their nine parents in the four agro-ecological zones of the country has shown a large phenotypic variability in the performance of the 27 genotypes for yield and its component traits. The hybrid N3A1 had the highest yield across the sites: 13 t/ha. Significant GXE interactions were detected for the four traits. The site, Adéta produced
more stable yield and number of panicles per plant though the lowest performance in all the traits was recorded at this site. All the traits were highly heritable (> 0.85) except for yield. The parent N5 had a significant general combining ability (GCA) for number of grains per panicle, and the hybrids N1A1 and N6A3 had significant specific combining ability (SCA) for 100-grain weight. No parent or hybrid had significant GCA or SCA for yield, showing the impossibility to develop F1 hybrid rice varieties for farmers with these 27 genotypes. However, the progeny families coming from the parent N5 viz N5A1, N5A2 and N5A3 will
be advanced using single seed descent selection method.
Programme:
PhD