Assessment of Genetic Diversity in West Africa Roselle (Hibiscus sabdariffa L.) Accessions by Morphological Evaluation and RAPD Genotyping

Roselle (Hibiscus sabdariffa L.) is an important crop purported to originate from West Africa where its economic importance as source of red anthocyanin-rich pigments, bast fiber, and leafy vegetable is ignored and little is done to collect, conserve and assess its genetic diversity. Genetic diversity studies reveal both useful genotypes and allele diversity for trait improvement. Little genetic variability exists in exotic roselle genotypes making trait improvement difficult. In this work, 39 roselle landraces collected from eight regions in West Africa, Bawku, Upper West, Ouagadougou, Lome, Senegal, Mali, Nigeria, and Cote D‟Ivoire were evaluated for agromorphological and RAPD genotyping. A large variability was found in calyx pigmentation, stem colour, and leaf lamina colour, all of which recorded 4 to 5 variants with substantial and fairly equal number of genotypes in each class. The large variability in quantitative traits estimated by coefficient of variability and mean square decreased in the order, leaf area 43.58% and 66,386.24, plant height 28.72% and 7,489.05, height at first branching 36.71% and 25.02, number of internodes 18.44% and 52.95, stem width 19.87% and 44.47, to branch number 27.66% and 5.48, respectively. Useful accessions identified were HS09, HS14, HS19, HS32 and HS50 from Ouagadougou, HS02 from Cote D‟Ivoire, HS69 from Bawku, and HS68 and HS86 from Mali for leafy vegetable production; HS20 and HS69 from Bawku, HS83 from Cote D‟Ivoire, HS04 from Lome, HS16, HS68, HS86 from Mali, HS09, HS14, HS19, HS24, HS50, and HS77 from Ouagadougou for high calyx productivity. For high fiber productivity, HS16 and HS68 from Mali, HS20 and HS69 from Bawku, HS13 from Nigeria, HS02 from Cote D‟Ivoire, and HS09, HS14, HS19, HS25, HS32, and HS50 from Ouagadougou were delineated on the basis of large values of plant height, stem width, and number of internodes. The predominantly low heritability estimates of 0 to 62% except for plant height represented dominance genetic effects that will achieve slow progress in breeding. All traits exhibited inconsistent genotype×environment effect across the populations. Low to moderate positive significant correlation coefficients of r =0.11 to 0.41 in plant height and number of internodes with all other traits was present. Genetic similarity based on morphological structuring ranged from 0.00 to 0.94 with mean of 0.27±0.26. UPGMA clustering split the accessions into three main clusters independent of their origin suggesting seed flow in the region. The first two principal components which accounted for 100% of the variance identified four uncorrelated groups and showed all traits to be correlated except height at first branching. Statistical analysis of 12 random decamer oligonucleotide genotyping revealed 80 to 100% rate of polymorphism, 1,297 alleles across genotypes, 63 alleles across loci, and average of 5.25 alleles per locus. Intra-locus gene diversity range of 0.15 to 0.32 and mean of 0.21±0.05 denoted higher allele diversity than exotic genotypes. Jaccard‟s similarity coefficient of 0.00 to 0.79 with average of 0.29±0.14 for the entire population uncovered substantial genetic diversity. UPGMA cluster analysis based on RAPDs grouped accessions into four major classes on a fair basis of their origin confirming the morphological PCA biplot analysis. Cluster I contained two heterogeneous subclusters IA and IB with average genetic similarities of 0.42±0.12 and 0.43±0.10 delineated a „Ouagadougou‟ and a „West African Mix‟ clusters, respectively. Cluster II was with similarity coefficient of 0.60±0.04 defined a „Ghana group‟. Cluster III, a single Senegal genotype, separated entirely from all accessions. Finally, cluster IV, having genetic similarity of 0.10 to 0.40 and average of 0.29± 0.11 represented a substantially large genetic diversity for a „Ouagadougou-Togo‟ mix. The region from Mali through Ouagadougou, Bawku to Lome was reckoned as the plausible center of roselle diversity. The large variability, polymorphism and allele diversity confirmed the Roselle landraces as rich reserve of allele diversity yet to be harnessed for crop improvement.

Source: KNUST