Genetic Variability and Path Analysis for Important Traits in Orange Fleshed Sweet Potato

Abstract

Estimation of genetic variability, genotypic and phenotypic correlation and inheritance of among agronomic traits is fundamental to improvement of any crop. Ten (10) OFSP genotypes were evaluated at the National Root Crop Research Institute, Umudike, Abia State , Nigeria, during 2014, 2015 and 2016 cropping seasons.The experiment was laid out in Randomized Complete Block Design with four replications to estimate correlations, genetic variability, heritability and genetic advance of root yield and its component characters in Orange-fleshed sweetpotato. There were significant differences among the genotypes (p ˂ 0.05) and in genotype by year interaction for total number of roots per plant, total root weight per plant and root yield. Correlation analysis revealed that significant positive correlation (p ˂ 0.05) coefficient (r) values involving root yield were 0.71 (p ˂ 0.05), 0.70 (p ˂ 0.05), and 0.50 (p ˂ 0.05), for root girth, total number of root per plant and root weight per plant respectively. Correlations between root yield and and root girth and between root yield and total number of root per plant were very high (r = 0.71 and 0.70 respectively). Path coefficient analysis for root yield (RY) showed that traits like, root girth (RG), total root weight per plant (TRWPP) and starch (SCH) had high positive direct contribution on RY (4.26, 2.65, and 2.25 respectively). Phenotypic (PCV) and genotypic coefficient of variations (GCV) were highest for beta carotene (98 and 97% respectively) and vine length at 18WAP (248 and 38.96% respectively) across the years. High heritability accompanied by low genetic advance for B-Carotene and vine length at 18WAP was indicative of predominance of non-additive gene actions which could be exploited through crossbreeding to take advantage of heterosis for these traits. Highest heritability was obtained for BCarotene, dry matter and Starch with each having 1. This was followed by vine length at 18wap (0.93) and internode length at 18WAP (0.81) across the years. This implied the presence of more additive gene effect and a potential for improvement in orange-fleshed sweet potato through selection. The genetic advance for dry matter (128.7), Starch(161.84), day to 50% flowering(22842.3), vine length at 18wap (175993.8) and root yield (665.08) were also high.