Abstract: A total of 5 pairs of diploid-triploid twin-seedlings were selected from 4500 pairs of SARⅡ-628 twin-seedlings. SSR analysis showed that there was no difference on 310 detected sites. A modified AFLP technique MSAP(methylation- sensitive AFLP) was employed to analyze methylation mutation. Although no methylation mutation was found in the 5 diploids, 29 methylation mutation sites were found in the corresponding triploids, which indicated that methylation mutation happened rapidly in M₀ generation after natural homologous triploidization. The mutations were classified into 10 types, including 3 increased types of methylation-degree, 3 decreased types and 4 undecided types. The fragments of 22 methylation sites were sequenced and then searched through website. The results showed that the methylation mutation involved into the whole rice genome. The mutation trend was site-related and there were different mutation sites for different triploids, which foretelled that SARⅡ-628 would undergo different evolution ways after natural homologous triploidization.

Key words: twin-seedling, diploid, triploidization, methylation, rice

摘要： 从4500对SARⅡ628的双胚苗中筛选出5对二倍体三倍体双胚苗。SSR分析显示它们在所检测的310个位点上没有差异。以AFLP为基础的MSAP（methylationsensitive AFLP）研究显示，5个二倍体在493个位点上甲基化状态没有差异。与二倍体比较，相应的三倍体虽然在甲基化总体水平上变化不大，但共有29个位点甲基化类型在不同单株上发生了变异，表明SARⅡ628自然同源三倍化后甲基化变异在M0代就迅速发生。变异共有10种类型，包括甲基化程度上升、下降各3种类型以及不定类型4种。对其中22个位点测序检索显示：这些甲基化变异涉及整个水稻基因组的12对染色体且具有位点特异性，不同单株的变异位点各不相同，预示着SARⅡ628不同单株在自然同源三倍化后将走向不同的命运。

关键词: 双胚苗, 二倍体, 三倍化, 甲基化