Inheritance and stability of earliness in potato (solanum tuberosum l.)
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Potato is an important food and cash crop in Uganda. Recent climate change characterized by erratic rainfall and elevated temperature have been recognized as major threat to potato production and productivity. Thus, breeding for adaptation to these conditions will be imperative to sustain potato production. This will require developing high yielding, short growth-cycle genotypes for both high and low elevations. Breeding strategies to guide development of such genotypes require understanding the mode of inheritance of earliness and its impact on potato tuber yield and quality. In order to address this, a study was designed with the aim of developing early maturing and high yielding potato cultivars adaptable to agro-ecologically diverse farming systems. Specifically, the objectives were to determine the mode of inheritance of earliness in potato and to determine the magnitude of genotype (G) by environment (E) interactions for earliness and fresh tuber yield in selected potato clones with horizontal resistance to late blight. To address the first objective, five late maturing potato clones with partial resistance to late blight were crossed with five early maturing but low yielding lines using a North Carolina 2 (NC2) design. The F1 progeny were evaluated and the combining abilities of parents showed that both additive and non additive gene effects controlled earliness though additive gene effects were more dominant. Parent 396038.107 portrayed good general combining ability for both earliness and high yield thus it can be used to improve potato genotypes for earliness and fresh tuber yield. To determine the magnitude of G x E interaction, nine advanced potato clones were evaluated across three sites located at different altitudes ranging from 1400 m to 2450 m above sea level for two seasons to estimate the magnitude of genotype by environment interaction and stability for earliness and fresh tuber yield. Genotype 396026.103 and 391046.14 were found to be the most stable for earliness and high fresh tuber yield across all the environments.