Adaptation of Commonly Grown Kenyan Potato Cultivars to Diverse Agro-ecological Zones

Abstract

Potato (Solanum tuberosum L.) grows best in cool areas where there is reliable water supply. Inadequate supply of water and elevated temperatures during growth and tuber formation significantly reduces tuber yield. Identification of potato genotypes that have a wider adaptation to different production environments that vary in temperature and humidity is increasingly becoming an important objective for potato variety development. The lack of stable and widely adapted potato varieties that can withstand the effects of unpredictable weather is a major contributor food and nutritional insecurity. Unstable and poorly adapted varieties are major limiting factors to potato production. This study aimed at evaluating and selecting genotypes that have broad adaptability, specific adaptation and stable for tuber yields across diverse environments. The approach was to test elite genotypes in different environments under conventional or farmers’ practices and intensive management (high input production) systems. Twenty-seven elite potato genotypes that were genetically diverse comprising of ten Table type genotypes and twenty-three Processing type genotypes were used in this evaluation. The genotypes were sourced from Kenya Agricultural and Livestock Research Organization (KALRO) and International Centre for Potato Improvement (CIP). The experimental design was Randomized Complete Block Design (RCBD) and replicated thrice. Genotypes, G5 G4 G6 G7 G9 G15 G16G18 G19 G21G23 G25 and G27 of the Table type and G1, G2, G3, G10, G12, G13, G14, G17, G22, G26 of the Processing type were screened in climatically diverse potato producing regions in Kenya during the long rainy seasons of 2015 and 2016. Each block measured, 35M by 11M with 1M spacing between blocks, 27 plots measuring 3 M by 3 M, and 1M foot path between plots. The genotypes were randomly allocated to plots and tuber yield data was scored at harvesting. The results indicated that genotypes interacted differently with the different environments. The genotypes and environments were also significantly different. The diversity in the genotypes and environments was the main factor that influenced variations in yield. This was an indication that the environments have elements that either favor potato tuber yield or act as limiting factors for tuber yields. These factors were mainly humidity and temperature. This was evident in the tuber yield variation across environment for each genotype. Regions with higher rainfall intensity and cooler temperatures during the growing period had higher yields compared to warmer regions with low and poorly distributed rainfall during the growing period. The levels of genotype by environment interactions were considered to be the main causes of the yield inconsistencies that were observed between genotypes and within genotypes in different environments. In conventional management, the genotypes and the environments were significantly different and, the genotypes also significantly interacted with the environment at (P<0.001). Narok location proved to be conducive for production of both Table and Processing type genotypes. The location had average yields of 29.26 t ha-1 28.15 t ha-1 for Table and Processing type genotypes respectively. These yields were significantly above the yields from other evaluation environments...................