カラシナ類（Ｂｒａｓｓｉｃａ　ｊｕｎｃｅａ）における生殖様式の品種間変異

In order to analyze the reproductive systems of brown mustard (Brassica juncea), variations in automatic self-pollination ability (ASPA) and degree of self-compatibility (DSC) within twenty-one cultivars of brown mustard were investigated in 1990, based on the percentage of seed set after automatic self-pollination or artificial self-pollination. The percentage of seed set after automatic self-pollination is an index of ASPA (Fig. 2), and the percentage of seed set after artificial self-pollination with a large number of pollen grains is an index of DSC. Relationships among ASPA, DSC and floral traits in eight cultivars selected from twenty-one cultivars of brown mustard were also investigated in 1991. The percentage of seed set after artificial self-pollination as an index of DSC ranged from 51.4% to 88.4%, and the percentage of seed set after automatic self-pollination as an index of ASPA ranged from 32.4% to 70.8%, showing variations in both traits within twenty-one cultivars. The percentage of seed set after automatic self-pollination in most of the cultivars was lower than that after artificial self-pollination (Table 1). These results suggest that a pollinator is indispensable for obtaining a sufficient number of seeds in most of the cultivars. Automatic self-pollination started when the anthers came into contact with the stigma or the time when the anthers dehisced after flowering, and continued for a few hours even though the anthers became separated from the stigma with time (Table 2, Fig. 3). Among eight cultivars, the number of pollen grains on the stigma after automatic self-pollination depended on the number of anthers in contact with the stigma, and the position of the anthers and the stigma (Table 6). Based on the time course of automatic self-pollination, in various cultivars the percentage of seed set increased by automatic self-pollination after flowering or after automatic self-pollination over a long period of time after flowering (Fig. 3). These results indicated that there were variations in the process of automatic self-pollination within the eight cultivars. The cultivars with higher ASPA and DSC values also showed smaller variations in several floral traits within a cultivar than those with low ASPA and DSC values (Table s 1 and 3). These results demonstrate that brown mustard displays variations within cultivars in self-compatibility, automatic self-pollination ability in relation to floral traits like contact between, or position of anther and stigma. These variations in the reproductive systems within cultivars suggest that there are wide variations in the need for pollinators in brown mustard cultivars which could be categorized as selfcompatible but incomplete selfers.