Life History of Wild and Weed Azuki Beans under Different Weeding Conditions

Abstract

Life history events were monitored in natural populations of wild azuki bean (Vigna angularis var. nipponensis (Ohwi) Ohwi et Ohashi) and weed azuki bean (Table 1) in order to clarify the relationship between life history traits (i. e. time of emergence, growth form, earliness) and ecological characteristics of their habitats with a view to promoting in-situ conservation of wild and weedy genetic resources of azuki bean.
In the habitat of wild and weed azuki beans, seeds predominantly germinated after weeding from late May to early October (Figs. 1, 2). In the vegetative stage, wild azuki bean rapidly expanded its vines and twined around other plants for climbing on top of the crown. Weed azuki bean usually showed an erect stem in open habitat, but it elongated its stem by leaning on other plants for climbing on top of the crown in the closed habitat. Both wild and weed races flowered in early September, while those in which germination was delayed flowered later (Figs. 1, 2). Mature pods were produced from early October to mid-November. After several days, they scattered seeds. Since reproductive success was very low (Table 3), natural populations were maintained with small individuals, and they built seed banks in the habitats. Weeding was usually practiced in every habitat (Table 3). The frequency of weeding in the habitat of weed azuki bean was slightly higher than that in the habitat of wild azuki bean. Average coverage in the weed azuki bean habitat was slightly lower than that in the wild azuki bean habitat (Table 2). Characteristics of their life history were closely related to the ecological features of their habitats. It is important to control the frequency of weeding to maintain individuals of wild and weed azuki beans in their habitats and to analyze the ecological characteristics of their habitats under weeding conditions to promote in-situ conservation of the two types of azuki beans.