同源四倍体水稻变异胚囊分类及结实性影响因素

Classification and Seed Set of Varied Embryo Sacs of Autotetraploid Rice

以秋水仙素加倍的同源四倍体水稻三系株系具有高比率的变异胚囊．各种胚囊变异类型在抽穗前1-2d的主穗和第一分蘖穗中出现频繁，造成正常胚囊的比率大幅降低．按变异胚囊的结构特点和形成方式，变异胚囊分为4种类型：退化型、结构变异型、无融合生殖型和反足细胞增殖型．退化型胚囊包括小胚囊和完全退化胚囊，前者仍有较小的胚囊腔而后者胚囊腔缺失；结构变异包括八核七细胞结构的缺失、重复和位置异常，反映了蓼型胚囊典型结构不同形式的变异；无融合生殖胚囊发生比率极低，主要包括反足胚和卵细胞胚；反足细胞的增殖比较频繁，这导致四倍体胚囊的多样性进一步增加，也对结实性带来一定影响．相关分析表明，同源四倍体水稻结实主要来自3部分：正常胚囊、正常型小胚囊和反足细胞增殖型胚囊．这3种胚囊可能具有较好的育性，其对结实率的贡献程度分别为正常蓼型胚囊的72．44％，正常型小胚囊的15．12％，反足细胞增殖型胚囊的12．44％；完全退化型胚囊和位置异常型胚囊对结实率分别表现出显著和极显著的负相关，表明二者可能是结实性的抑制因素．

Autotetraploid strains which are developed from diploid individuals by colchicine treatments exhibit high variation rates of embryo sacs. Abnormal embryo sacs frequently occur in the spikelets of main panicles and the first tillers 1-2 d before heading, leading to obvious decreases in the degrees of normal embryo sacs among the strains. The varied embryo sacs are classified into four types according to their different structures and origins： Degenerated embryo sac （DES）, structure variation （SV）, apomixis （Apo） and antipodal cell proliferation （ACP）. The DES exhibits small embryo sac or no embryo sac, with the former showing a small sac and the latter showing no sac. The SV includes deletion, duplication and location variation, which suggests the occurrence of the variations of the eight nuclei, seven celled embryo sacs of the Polygonum type. The Apo occurs at very low frequency and includes antipodal embryo and egg embryo. The ACP frequently occurs in autotetraploid rice that leads to the increase in diversity of the embryo sacs and simultaneously influences seed germination. The Pearson＇s correlation analysis shows that seed set is contributed by three main parts： normal embryo sac, small embryo sac with normal pattern and embryo sac with antipodal proliferation. These embryo sacs may be highly fertile and account for 72.44%, 15.12%, 12.44% of seed set, respectively. The NES is negatively related to seed set at the P〉0.01 level and the LV negatively related to seed set at the P〉0.05 level, which suggests strong stress on seed set by the two types. Tab 2, Fig 2, Ref24