Male and female fertility in triploid grapes (Vitis complex) with special reference to the production of aneuploid plants

To produce aneuploid plants, the extent of male and female fertility in triploid grapes was studied using 187 triploid hybrid plants obtained from 2x × 4x and 4x × 2x crosses. In the triploid plants, pollen germination rates examined on agar medium ranged from 0 to 5.88 % (average: 0.24 %). In 86 out of the 187 triploid plants none of the pollen grains germinated. In the 3x × 2x and 3x × 4x crosses, 10 triploid plants showing more than 1 % pollen germination rates produced 191 seeds from 7,692 pollinations and 109 seeds from 3,862 pollinations, respectively, whereas 10 triploid plants showing no pollen germination produced 98 seeds from 5,282 pollinations and 141 seeds from 5,293 pollinations, respectively. In the 3x × 2x and 3x × 4x crosses, the percentage of ovules developing into seeds varied in different triploid hybrid plants and ranged from 0.1 to 2.3 %. Of 8 aneuploid plants derived from the 3x × 2x and 3x × 4x crosses, one grew normally, three showed slow growth rates and 5 plants died after germination. These results suggest that in triploid grapes (1) there is no relationship between the degree of male fertility and that of female fertility, but the degree of the fertility is a triploid-plant-specific character, (2) female fertility is slightly higher than male fertility, and (3) male and female fertility is very low but aneuploid plants can be produced if triploid grapes with more than 0.3 % female fertility are used as seed parents.