Abstract
We carried out colchicine treatment of lateral buds and their grafting in some monoembryonic citrus cultivars to induce tetraploid plants. Among the grafted plants, 19 eutetraploid plants were obtained from 8 cultivars. The successful cultivars were ‘Ootachibana’, ‘Suisho-buntan’, ‘Nouma-benihassaku’, ‘Kiyomi’, ‘Aki-tangor’ ‘Nishinokaori’, ‘Ariake’ and ‘Hiroshimakaken No. 11’. Then efficiency of triploid production was very high (7.68 triploid/fruit) when the tetraploid ‘Kiyomi’ were used as a seed parent. The efficiency was higher than those for crossing trials of diploid ‘Kiyomi’ × diploid ‘Ootachibana’ (0.05 triploid/a fruit) and diploid ‘Kiyomi’ × the tetraploid ‘Ootachibana’ (0.16 triploids/a fruit). In addition, when some other monoembryonic tetraploids were crossed with diploid cultivars, they also bore triploid plants efficiently as seed parents, such as 0.47–0.91 in the tetraploid ‘Ariake’, 2.13–2.86 in the tetraploid ‘Hyuganatsu’, 4.25–6.00 in tetraploid ‘Clementine’, 6.79–11.33 in tetraploid ‘Kiyomi’. Although the sizes of the hybrid seeds were smaller than the averaged diploid seeds, but the seeds matured fully and germinated well (79.1%) in vitro. This study showed that 99.8% of the raised hybrid plants were triploid (487 plants).
