GENETIC VARIABILITY AND ASSOCIATION OF TRAITS IN DROUGHT TOLERANT POTATO (Solanum tuberosum L.) GENOTYPES IN SIMADA DISTRICT, NORTH WESTERN ETHIOPIA

Abstract

Development of drought tolerant potato varieties for moisture stress areas is one of the strategic orientation and research priorities of the Ethiopian Potato Research Program. Estimation of variability is the first step in the process of variety development. This research was conducted at Simada research site of Adet Agricultural Research Center, a satellite site for drought experiments, in 2016 main rain season to estimate genetic variability, correlation among traits and to determine genetic diversity among 105 potato genotypes that included five checks. The experiment was laid out in Augmented design and data were collected for 20 traits. The analysis of variance revealed the presence of highly significant (P<0.01) differences among genotypes for all traits considered except plant height and small and medium size tubers percentage. Marketable and total tuber yield ranged from 10.81 to 38.99 and 13.92 to 41.79 ton ha-1, respectively. Three new entries (20SET4.2, 20SET4.1 and 16SET5.5) had total tuber yield advantage of 35 to 51% over the best yielding check (Belete). Phenotypic (PCV) and genotypic (GCV) coefficient of variation values ranged from 1.86 (SG) to 32.8 (LTP), and 1.3 (SG) to 25.5% (LTP), respectively, while heritability and genetic advance as percent of mean estimates ranged from 45.95(LA) to 89.15% (TNP) and 3.33 (SG) to 40.89% (UMY), respectively. Moderate to high GCV, PCV, H2 and GAM were estimated for stem number per plant, tuber number and yield per plant, average tuber weight, unmarketable and marketable yield, bulking rate per plot, very small and large size tubers percentage and total starch content, suggesting selection breeding is effective to improve these traits. Total tuber yield showed significant and positive correlation with leaf area, tuber number per plant, tuber yield per plant, marketable tuber yield, bulking rate, large size tubers percentage and average tuber weight, but significant negative correlation was observed with very small tuber percentage. Thus, selection for positively correlated traits will simultaneously increase the total tuber yield. Genetic distances of genotypes measured by Euclidean distance ranged from 1.11 to 12.60 and the dendrogram constructed by using the Unweighted Pair Group Method using Arithmetic means (UPGMA) grouped genotypes into 20 major clusters. The genotypes in different clusters are characterized by one or more desirable traits with wide range of intra and inter clusters mean genetic distances suggesting a higher chance of developing varieties through direct selection or crossing to produce heterotic hybrids.