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Pollen Tube Growth, Fertilization and Seed Development in Hyuganatsu (Citrus tamurana) Seedless Cultivars 'Muroto-Konatsu' and 'Nishiuchi-Konatsu'

2001; Japanese Society for Horticultural Science; Volume: 70; Issue: 3 Linguagem: Inglês

10.2503/jjshs.70.320

1880-358X

Akira Kitajima, Y. Okada, Kojiro Hasegawa,

Horticultural and Viticultural Research

'Muroto-Konatsu' and 'Nishiuchi-Konatsu' are seedless bud mutants of Hyuganatsu (Citrus tamurana) which were examined for their bases of seedlessness. 1. There were no significant differences in the numbers of ovules and locules per ovary among 'Muroto-Konatsu', 'Nishiuchi-Konatsu' and common type Hyuganatsu. 2. When 'Muroto-Konatsu', 'Nishiuchi-Konatsu' and the common type were pollinated with pollen from 'Suisho-Buntan' pummelo, the pollen tubes barely penetrated the pistil of 'Muroto-Konatsu', whereas they grew down to the ovary of 'Nishiuchi-Konatsu' and the common type. Hence, 'Muroto-Konatsu' had a few fertilized ovules which failed to set seeds, whereas 'Nishiuchi-Konatsu' and the common type had the same number of pollen tubes in the upper part of their ovaries 14 day after pollination and set an equal of fertilized ovules and seeds. 3. Self-pollination and reciprocal pollination were performed in 'Nishiuchi-Konatsu' and the common type. In self-pollinated 'Nishiuchi-Konatsu', the pollen tubes penetrated into upper part of the ovary. Hence, a few fertilized ovules were produced. In reciprocal pollinated 'Nishiuchi-Konatsu' and the common type and self-pollinated the common type, the pollen tubes penetrated only into middle part of the styles. Hence no fertilized ovules were produced. These data indicate that the seedlessness of 'Muroto-Konatsu' results from the inhibition of pollen tube growth into the pistil when cross-pollinated, whereas in 'Nishiuchi-Konatsu', which is partially self-compatible, it is nearly always seedless because of poor pollen growth when self-pollinated. We conclude that seedless cultivars 'Muroto-Konatsu' and 'Nishiuchi-Konatsu' mutated in the characters of the pistils on cross-compatible and self-incompatible, respectively.