Studies on the break of self-incompatibility and seed abortion by 'Nishiuchi Konatsu' Hyuganatsu self-pollination

Hyuganatsu(柑橘Tamurana hort ex Tanaka)最初是自交不亲和。它的花蕾突变‘西口小松’是自交亲和的，当‘西口小松’自花授粉时，种子在发育过程中就会败育。我们假设‘西口小松’中存在未还原的花粉。为此，我们对‘西口小松’及其后代的花粉萌发、花粉直径和倍性水平进行了研究。在花粉萌发试验中，‘西口小松’花粉与其他品种相比具有正常的萌发能力。然而，西口小松被发现部分产生了巨大的花粉，这证明了许多其他植物中存在未还原的花粉。在倍性水平的流式细胞术分析中，‘西口小松’本身就是二倍体。而‘西口实生’自花授粉后发育的种子全部表现为四倍体。这些结果表明，‘西口小松’部分产生不还原的花粉，只有不还原的花粉才能到达胚珠进行杂交。只有在未减数花粉受精的胚珠不减数的情况下，种子才能成功发育为四倍体。

Hyuganatsu (Citrus tamurana hort ex Tanaka) is originally self-incompatible. Its bud mutation 'Nishiuchi Konatsu' is self-compatible and seed is aborted during its development when 'Nishiuchi Konatsu' is self-pollinated. We assumed the presence of unreduced pollen in 'Nishiuchi Konatsu'. Thus we studied pollen germination, pollen diameter, and ploidy level of 'Nishiuchi Konatsu' and its progenies. In the result of pollen germination test, 'Nishiuchi Konatsu' pollen has normal germination ability compared with other varieties. However, it was revealed that 'Nishiuchi Konatsu' partially produced giant pollen, which is the proof of the presence of unreduced pollen in many of other plant species. In the flowcytometry analysis for ploidy level, 'Nishiuchi Konatsu' itself was diploid. However, all the seedlings from the developed seed of 'Nishiuchi Kontasu' self-pollination indicated tetraploidy. These results suggested that 'Nishiuchi Konatsu' produced unreduced pollen in part and only unreduced pollen can reach to the ovule to hybridize. Only when ovule fertilized with unreduced pollen was unreduced, seed was successfully developed to be indicated tetraploid by flowcytometry.