Reproductive Traits of Hermaphroditic Muscadine Cultivars

Abstract

Native muscadines (Vitis rotundifolia Michx.) are dioecious, but muscadine vineyards are usually planted with a mixture of female plants and hermaphroditic pollenizers. Hermaphroditic cultivars are derived from either of two separate sources original hermaphroditic plants, H1 or H2. Nine hermaphroditic and two female cultivars were studied to determine their potential as pollenizers. Inflorescences of each cultivar were collected in the field to evaluate the number of anthers per flower, the number of pollen grains per anther, and pollen viability and germination in the main and secondary flowering periods. The number of flower clusters per shoot ranged from one to four with most producing two or three flower clusters per shoot. The number of anthers per flower varied by cultivar and cluster position, but in general was between six and eight anthers per flower. ‘Noble’ showed the highest pollen grains production per anther and per flower, reaching 5777 and 39,860, respectively, in the first cluster and ‘Carlos’ produced the least amount of pollen. All cultivars that had secondary flowering showed lower pollen production per anther and per flower as compared with the main flowering period. Optimal muscadine pollen germination media contained 50 mg·L−1 boric acid, 145 mg·L−1 calcium nitrate, 188 g·L−1 sucrose, 10 g·L−1 agar, and 10 mm 2-(N-morpholino)ethanesulfonic acid (MES) pH 6.0. The pollen grain viability of hermaphroditic and female cultivars was high, but pollen grain germination was low in hermaphroditic cultivars and absent in female cultivars. H1-derived cultivars produced more flower buds per cluster and higher germination rates than H2-derived cultivars, indicating they may be better pollenizers. Chemical names used: 2-(N-morpholino)ethanesulfonic acid (MES).