2017 Volume 16 Issue 4 Pages 409-414
‘Natsumi seedless’ is a new citrus cultivar that produces fewer seeds than the original cultivar, ‘Natsumi.’ ‘Natsumi seedless’ was produced by soft-X irradiation of the scions of ‘Natsumi.’ After top-grafting those scions, a strain was selected on the basis of few seeds per fruit. The average number of seeds in ‘Natsumi’ was 8.9 per fruit, and the rate of its seedless fruit was 0 percent. On the other hand, the number of seeds in the new cultivar was 0.2 seeds per fruit, which was extremely few, and the rate of its seedless fruit was high at 86.7%. With the exception of the number of seeds, the characteristics of fruit and trees of the new cultivar were similar to those of ‘Natsumi’. The possibility of female sterility in ‘Natsumi seedless’ was shown by cross-pollination between Natsudaidai, as a pollen parent, and two cultivars, ‘Natsumi’ and the new cultivar, as a seed parent, revealing that only the new cultivar had seedless fruit and its rate was high. In addition, male sterility in the new cultivar was indicated by two findings: First, the pollen fertility of the new cultivar was 1.9%, being noticeably lower than that of Natsudaidai or ‘Natsumi’. Second, cross-pollination between the new cultivar (pollen parent) and Natsudaidai (seed parent) resulted in it not bearing fruit, while it bore fruit when the pollen parent was ‘Natsumi’. From these results, the new cultivar, ‘Natsumi seedless’, may have both female and male sterilities.
