Dissecting the Ghana roselle (hibiscus sabdariffa var. Altissima) accessions for genetic diversity using agro-morphological evaluation

Roselle altissima is a bast fiber crop of global economic importance. Although West Africa is considered the centre of diversity, research and utilization in roselle is widely ignored. The awakening of industrialization in Ghana presents roselle as candidate crop for exploration, however, information on genotypes of economic importance is lacking. Characterization and genetic diversity estimation identifies genotypes having important traits for incorporation into breeding programmes, and reveal within and between population variability, divergence between genotypes and relationships among them. Our objective was to map roselle geographical origin in northern Ghana, determine regions of substantial genetic diversity, examine genetic variability, estimate the distance within the collection, and identify relationships in the genotypes. Sixty-one accessions collected from 21 districts were evaluated in a two-season field trial using a 6 × 6 lattice square design for 36 accessions and 5 × 5 lattice square design for 25 accessions in three replications each from July to November 2016 and 2017, respectively. The genotypes were evaluated using twelve qualitative and five quantitative morphological traits covering plant type, leaf, stem and flower characteristics, and growth habit. Data were analysed by Shannon-Weiner Diversity Index (SDI), analysis of variance, genetic distance, cluster, principal component, and stepwise discriminant analysis. Except for conserved traits in growth habit, calyx pubescence, and capsule shape, large variability was observed in plant type, branching habit, stem pubescence, leaf form, and calyx pigmentation. Large between population differences were identified in plant height, branch number, basal diameter, and days to flowering. A large within population variation of 0.74 to 0.85 for branch number, plant height, basal diameter, and days to flowering resided in the accessions. Height after first branching was somewhat identical in season 1. Mean plant height ranged from 184 cm to 355 cm, basal diameter 13 mm to 24 mm, height at first branching 6 cm to 157 cm, branch number 2 to 12, and days to 50 % flowering from 97 to 101 days after planting. Twenty-one accessions were selected based on tall plant height with few branches at high branch points, and large basal diameter were HA-07, HA-11, HA-12, HA-21, HA-33, HA-37, HA-38, HA-39, HA-42, HA-43, HA-44, HA-45, HA-46, HA-47, HA-49, HA-50, HA-52, HA-54, HA-55, HA-57, and HA-58. Seven districts exhibited largest diversity by SDI estimates Kassena-Nankana (0.87), Bolgatanga Municipal (0.83), West Mamprusi (0.82), Savelugu-Nanton (0.73), Tamale Metropolitan (0.68), Gowri-Yorogo and Talensi (0.67). Mean district SDI values ranged from 0.53 to 0.87. Savelugu-Nanton district accessions had the highest mean plant height of 308.27 ± 48.91 cm, highest branching point at 107.19 ± 64.66 cm, and less than five branches. Low correlation coefficients of r = 0.11 in plant height and basal diameter to r =0.13 in plant height and branch number was identified. Mean genetic distance based on Euclidean estimate was 3.03 ± 0.90 and ranged from 0.41 to 5.17 representing substantial genetic diversity in the region. Clustering based on Ward’s minimum variance produced three clusters independent of their geographical origin suggesting seed flow in the region. The first three principal components explained 100 % of the total variance with the highest loadings from branch number, height at first branching and basal diameter, then plant height and days to 50 % flowering. Stepwise discriminant analysis identified branch number, plant height and days to 50 % flowering to be most important traits in the structuring of roselle altissima. The findings would be beneficial for planning a systematic collection, for conservation, and for trait improvement in breeding roselle.

Source: KNUST