Abstract:
Potato (Solanum tuberosum L.) is a highly heterozygous and has complex tetrasomic inheritance that make difficult to understand the inheritance of traits and implement in hybridization program. However, the genetic variation created in F1 generation could be exploited through asexual propagation. Research efforts carried out in Ethiopia related to improving potato through crossing were limited in scope of breeding works. Thus, this study was conducted at Adet in 2018 to assess the genetic variability among crosses of potato varieties, to estimate the magnitude of heterosis in crosses of potato varieties and assesses the association among agro-morphological traits. A total of 81 which 75 clones, five parents and one standard check varieties were evaluated for 18 traits in 9 x 9 simple lattice design. The results of analysis of variance revealed the presence of highly significant differences among crosses for all quantitative traits except for percentages of medium size tubers and specific gravity. Marketable and total tuber yield of genotypes ranged from 2.51 to 55.62 t ha-1 and 10.82 (J x A.333) to 58.31 t ha-,1 (B x A.164), respectively. The dry matter content and starch content also ranged from 13.78 to 29% and 8.28 to 21.84%, respectively. The range of mid (MPH) and better parent (BPH) heterosis for total tuber yield were between -64.06 to 79.36% (B x A.164) and -72.59 to 61.04% (J x A.119), respectively, while standard heterosis (SH) was in the range between -42.63 to 209.17% (B x A.164). The F1 progenies obtained from crosses of Jalene and Ater ababa exhibited the highest positive and significant MPH, BPH and SH as compared to F1 clonal progenies obtained from crosses of other varieties. The phenotypic (PCV) and genotypic (GCV) coefficient of variations ranged between 4.67 to 92.88% and 3.25 to 73.5%, respectively. Heritability in broad sense (Hb) and genetic advance as percent of mean (GAM) ranged from 28.81 to 91.64% and 4.65 to 98.81%, respectively. The lowest and highest Hb (%) estimated to proportion of small size tubers and highest days to flowering, while the lowest and highest values PCV, GCV and GAM were computed to days to maturity and unmarketable tuber yield, respectively, for other three variability components (PCV, GCV and GAM). Total tuber yield had positive and significant phenotypic and genotypic correlations with stem height, tuber yield per plant, tuber number per plant, average tuber weight, marketable tuber number and marketable tuber yield. Days to plant emergency, days to maturity, marketable tuber number, dry matter, proportion of small and large size tubers had positive direct effect on total tuber yield at phenotypic and genotypic level. Traits such as tuber number per plant, percentages of large tubers and average tuber weight had high estimates of PCV, GCV, Hb and GAM suggested that could be used as selection of genotypes for high potato tuber yield. The first four principal components (PCA) accounted 72.7% of the total variations of F1 clonal progenies and varieties of which PCA1 accounted 33.8% of the variations in which total yield per hectare, tuber yield per plant, marketable tuber yield and stem height much contributed to PCAI. Euclidean distances as estimate of the genetic distances of F1 clonal progenies and varieties ranged from 1.57 to 14.35 with mean of 5.77. The most distant F1 clonal progenies were found in crosses of Belete and Ater Ababa. F1 clonal progenies and varieties were grouped in to16 clusters of which Cluster V consisted of 23.46%, while Cluster I, VI and XII consisted of 18.52, 16.05 and 9.88% of F1 clonal progenies and varieties, respectively. Five clusters (III, XI, XIII, XV and XVI) each consisted of one genotype and the other clusters consisted 2.47 to 6.17% of genotypes. In conclusion, this study showed the presence of genetic variation among crosses of varieties for yield, yield related traits indicating the success of crossing program in the country.