Chromosome Number of the Original Tree and Open-pollinated Progenies of Japanese Persimmon, cv. Hiratanenashi

Abstract

Chromosome numbers of the original tree and embryos exised from immature or aborted seeds of Japanese persimmon cv. Hiratanenashi were examined. The possible origin of the tree and the reason for seedlessness in ‘Hiratanenashi’ based on chromosome number are discussed.
1. The original ‘Hiratanenashi’ tree, a chance seedling, has a somatic chromosome number, 2n=135. Accordingly, the tree was considered to have originated from a union of an unreduced gamete (n=90) and a reduced gamete (n=45) of the same species; ‘Tone Wase’, a spontaneous bud sport of ‘Hiratanenashi’, also has 135 chromosomes in its somatic cells.
2. Differences in the degree of embryo development were observed among immature embryos 80 days after anthesis and embryos cultured on artificial medium. These differences indicate that the development and growth of ‘Hiratanenashi’ embryos are related to its genotype.
3. The somatic chromosome number of the embryos derived from immature or aborted seeds of ‘Hiratanenashi’ and ‘Tone Wase’ ranged from 106 to 114. This suggests that the embryos were aneuploid and that the gametes of heteroploidy were derived from their mother plants, ‘Hiratanenashi’ and ‘Tone Wase’.
4. We postulate that the main factor preventing normal seed development in ‘Hiratanenashi’ persimmon is the formation of abnormal embryo sacs and heteroploid gametes. The unbalanced chromosome numbers in gametes must lead to abnormal cell division and subsequently the degradation of endosperms and embryos.