Genetic diversity of cassava (Manihot esculenta Crantz) varieties grown in Daloa district in Central-Western Cte dIvoire

Cassava is an important staple food in Cote d'Ivoire produced in several areas including the Daloa district in Central-Western Region. However, this plant experiences biotic and abiotic constraints that strongly limit its productivity. Proper knowledge of genetic diversity is important to mitigate these constraints and select resistant and well adapted genotypes to increase the productivity. This study assesses the genetic diversity of four varieties of cassava (Bocou 1, Bonoua, Yace and Yavo) cultivated in Daloa. A total of 266 samples of leaves were collected and genomic DNA was genotyped with 5 simple sequence repeats (SSR) microsatellite markers. In all, 28 alleles were recorded from all the loci with an average number of alleles ranging from 2.6 to 2.9. The average heterozygosity obtained for all loci was higher than expected (p = 0.008) and significant genetic diversity was observed within all the varieties (Fis = -0.43, p=0.02) for Bocou1, (Fis = -0.59, p = 6.10-4) for Bonoua, (Fis = -0.32, p = 0.05) for Yace and (Fis = -0.38, p=0.02) for Yavo. A strong genetic differentiation were also observed between varieties, except between varieties Bocou1 and Bonoua where differentiation was moderate (Fst = 0.13). Genetic structure of the population exhibited two or three clusters depending of the variety which might be due to the continuous exchange of plant materials among farmers, selection-base varieties, and use of several varieties in the same fields. This study provides improved understanding of the genetic basis of the varieties which can be exploited to fight against biotic and abiotic stresses in this area. Key words: Cassava, Cote d'Ivoire, Daloa, genetic diversity, Manihot esculenta, microsatellite, population structure.