A Leaf wilting in sugar beet (Beta vulgaris L.) based on varietal difference of root system

Abstract

Thirteen varieties/strains of sugar beet were cultivated in haplic andosol and the relationship between root system distribution and resistance to high temperature and dry soil conditions was investigated during the hot summer of 2006. We found that there were clear differences on the degree of leaf wilting among thirteen varieties/strains. When leaves of other varieties had wilted despite closing stomata to reduce water loss, the leaves of ‘Kabutomaru’ did not wilt. Based on the degree of leaf wilting, ‘Kabutomaru’, ‘Stout’ and ‘Ascend’ were selected and their diffusion conductance was measured. Under high temperature and dry soil condition, ‘Kabutomaru’ maintained high diffusion conductance values. ‘Ascend’, which had the greatest degree of wilting, had low values with a photosynthetic rate not exceeding 50%-60% at stomata full opening. Diffusion conductance of ‘Stout’ was intermediate between that of the other varieties. Root system spreading was also examined. In contrast to the deep root system of ‘Kabutomaru’, ‘Ascend’ and ‘Stout’ had shallow root systems. In summary, the vertical distribution of root systems varied among sugar beet varieties, and the deeper the root system, the greater the plant's ability to take up water from deeper levels during hot, dry conditions and to resist wilting. In Abashiri City, Hokkaido where this research was conducted, poorer soil conditions result in shallower sugar beet roots and lower yield per area. Although several points require further consideration, the deep root systems that characterize ‘Kabutomaru’ provide hope for improving harvest stability.