GENETIC VARIABILITY FOR YIELD, YIELD RELATED TRAITS AND REACTION TO LATE BLIGHT IN POTATO (Solanum tuberosum L.) GENOTYPES AT SINANA, SOUTH EASTERN ETHIOPIA

Abstract

The highlands of Bale is known with potato production, but the productivity of the crop is low due to the growing of low yielding genotypes susceptible to late blight. This needs to develop varieties with high yield and resistant to late blight. Therefore, this study was conducted to evaluate 24 potato genotypes with the objective of assessing the nature and magnitude of variability for tuber yield, yield related and late blight resistance traits, and association of tuber yield with other traits. The experiment was laid out in randomized complete block design with three replications at Sinana Agricultural Research Center. The genotypes showed highly significant (P<0.01) differences for all the characters studied, except for starch and specific gravity. Genotypes exhibited wide ranges of mean values for all characters. The highest total tuber yield (46.1 t ha-1) was obtained from the advanced clone, CIP-392640.524 followed by Belete (41t.ha-1). Late blight appeared early on farmers cultivar Kellacho (48 days after planting) and lately on CIP-399062.102(74 days after planting)). Percent severity index (PSI) and area under disease curve (AUDPC) ranged between 33-39.7% and 105 to 2370, respectively, for 11 newly introduced clones and the released variety Belete. These genotypes can be categorized as moderately resistances. Other genotypes had higher PSI and AUDPC and fall under late blight susceptible category. High genotypic (GCV) and phenotypic (PCV) coefficient of variations computed which ranged from 22.7 to 51.9% and from 32.8 to 56.7%, respectively, for all the traits except for days to maturity with low values computed for both. Heritability in broad sense (H2) and genetic advance as percent of the mean (GAM at 5% selection intensity) ranged from 44.5 to 89.5% and 14 to 98.1%, respectively. Both H2 and GAM high for total tuber yield, marketable tuber yield, average tuber weight, marketable tuber number per hill, percent severity index, days to flowering, area under disease progress curve and days to late blight appearance. This suggested these traits are amenable to selection. Marketable tuber yield, average tuber weight, marketable tuber number per hill and stem number per plant had high and positive direct effect on total tuber yield, while unmarketable tuber yield, unmarketable tuber number per hill, percent severity index and area under disease progress curve on total tuber yield had negative direct effects. Various other characters also influenced the total tuber yield favorably or unfavorably via other characters. This suggested the importance of selecting of genotypes with high and low mean values for the traits that showed positive and negative direct and indirect effects on yield, respectively. The study revealed that the presence of considerable variability in tested genotypes for economic importance traits and the higher chance of selecting genotypes with high yield and moderately resistant to late blight. But it is necessary to continue the evaluation of genotypes across seasons and locations to identify genotypes that could be approved as variety for the study area