Abstract
This study was conducted to present a quantitative analysis of the branching pattern of the sweet potato over growth time and its varietal differences of the two cultivars, Shiroyutaka and Minamiyutaka. 1. Primary and secondary branches in Shiroyutaka were developed significantly during 30 to 60 days after planting. Most of such branches were formed at the base of the plant, and they tended to have grown more rapidly than in the branches formed on the other part of the plant axes. In Minamiyutaka, on the other hand, branching ability was relatively low, especially very few branches were formed at the base of the plant. Based on the difference in such a branching habit of the two cultivars, the dry matter of the vegetative top in Shiroyutaka showed heavier than that of Minamiyutaka through all the growth period. 2. The diameter at the base of the main stem was observed to increase in close relation to the development of the branches formed at the base of the plant. Shiroyutaka, compared with Minamiyutaka, increased its diameter significantly during the growth periods of both primary and secondary branches. This increase was owed mainly to the increase in the secondary vascular tissues. 3. The tuberous root yields in Shiroyutaka were higher than in Minamiyutaka through each time of the growth stage. Based on these results, it is suggested that early development of the branches formed at the base of the plant promoted the growth rate of the vegetative top and the yield of tuberous roots. Additionally, the increase in diameter at the base of the main stem might have some advantage in relation to the translocation of the substance.
