Dormancy and Physiological Age of Seed Tubers from a Diverse Set of Potato Cultivars Grown at Different Altitudes and in Different Seasons in Kenya

Abstract

The study was conducted to determine the dormancy and physiological age characteristics of diverse potato genotypes as influenced by growing altitudes and seasons for future breeding strategies and optimal patterns of use. Dormancy and sprouting characteristics have an impact on tuber production, storability and seed quality for planting and ware for consumption and the market. This study presents the results of dormancy and physiological age measurements conducted on 47 potato genotypes grown at three altitudes with three replications at each location and in two contrasting growing seasons. The seed tubers were evaluated at low altitude under darkness on moist sand storage conditions to assess their dormancy release, number of sprouts, sprout weight, sprout length and percentage tuber weight loss. Results showed significant (p < 0.001) differences among genotypes, locations and seasons, and significant interactions between these factors for days to dormancy release, number of sprouts per tuber at dormancy release and at 45 days after dormancy release, length of longest sprout, weight loss percentage of unsprouted and sprouted tubers at dormancy release and at 45 days after dormancy release, respectively. There was a wide variation in time to dormancy release (54 to 136 days); most genotypes showed medium to long dormancy. Seed tubers grown at low altitude showed longer dormancy than those grown at higher altitudes, while genotypic differences in dormancy were very consistent across environments. Genotypes strongly differed in sprouting characteristics and weight loss. There were highly significant interactions between altitude and season for all variables assessed, except for the number of sprouts 45 days after dormancy release and the weight loss after sprouting. Generally, the genotypic effects were larger than those of altitude, season and the interaction effects for all variables evaluated. This paper will allow variety selection to optimize seed quality at planting and minimize storage losses while providing new targets for breeders.