DR. KOUSSAO, SOME

GENETIC IMPROVEMENT OF SWEETPOTATO (Ipomoea batatas [L.] Lam) FOR BETA-CAROTENE AND YIELD IN BURKINA FASO, ABSTRACT

The potential of sweet potato to address food security, malnutrition and poverty is acknowledged in Sub-Saharan Africa. The present study was undertaken to develop varieties combining yield and quality in order to address food security and malnutrition in Burkina Faso.

Participatory Rural Appraisal was conducted to identify farmers’ and consumers’ production constraints and preferences. One hundred and twelve accessions were collected to study the variation that exists and can be exploited to address the end-users’ needs. Eight parents comprising five farmers’ cultivars with various flesh colour and three introduced orange-fleshed sweetpotato varieties were selected to develop populations and, subsequently, to estimate heritability and genetic gain from breeding. Thirty three F1 orange-fleshed genotypes were evaluated in three locations in an Alpha Lattice design to identify high yielding and beta-carotene rich clones with specific to wide adaptation to the local environments. Low productivity of cultivars due to reduced cropping cycle, declining soil fertility, susceptibility to weevil and virus were identified as major constraints in sweetpotato production. The PRA revealed that farmers’ preferences were for orange-fleshed sweetpotato varieties that combine high and stable yield, high dry matter content, good storage ability, good vegetative growth, early maturity and storage root with preferred shape. High to moderate diversity coefficient of 0.73 and 0.49 was observed among the accessions using morphological descriptors and SSR markers, respectively. Parent-offspring regression analyses and estimated genetic gain suggested rapid progress in dry matter content with high heritability (0.76±0.03) and high genetic gain (22.60%) and in beta-carotene content that was also highly heritable (0.90±0.04). Low heritability (0.21±0.16) associated with low genetic gain indicated that increased storage root yield would be more difficult to attain. Genotype by environment analysis indicated that genotype effects accounted for 83.42% of the variation of beta-carotene content, while genotype by environment effects accounted for a higher source of variation for dry matter content and storage root yield. The AMMI model was able to identify genotypes for specific environments as well as widely adapted genotypes. The best F1 genotypes for yield (BF82xTainung-8 with 20.33 t/ha) and for beta-carotene (BF82xTIB-8 with 10.85 mg/100g of fresh weight) showed 82.99% and 32.64% increase respectively for yield and beta-carotene content over the performance of the best checks for storage root yield (CIP-199062-1 with 11.5 t/ha) and beta-carotene content (BF14 with 8.18 mg/100g of fresh weight). However, the best F1 genotype for dry matter content, BF82xTainung-11 with 32.15% had 4.29 % dry matter less than the best check, Caromex with 32.59%.