不同倍性栽培稻与药用野生稻种间杂交不结实性的比较胚胎学观察

Comparatively Embryological Observations on Interspecific Hybridizations Between Oryza sativa with Different Ploidy Levels and O. officinalis

以栽培稻(Oryza sativa)品种L202二倍体(L202-2x)及其同源四倍体(L202-4x)作母本分别与药用野生稻(Oryza of ficinalis)杂交,比较了两个杂交组合的杂交结实性及影响结实性的杂种胚胎发育细胞学。两个杂交组合所取得的一致结果是:杂交授粉后30d所有杂交小穗均干枯死亡,不能结实;种间杂交不结实的原因在于受精和杂种胚胎胚乳发育异常。两个杂交组合的受精和杂种胚胎胚乳发育虽然均存在双受精、单受精和未受精类型,但就受精率而言,L202-2x作母本的平均总受精率为59.45%,略高于L202-4x(54.87%);L202-4x的单受精率(24.60%)则高于L202-2x的单受精率(15.30%)。两个杂交组合的杂种胚胎胚乳发育均严重异常,虽然在授粉后1d形成小的球形胚;到授粉后3d,胚胎发育停滞并开始解体;至授粉后5d,只有二倍体杂交组合的极少数胚胎可发育到梨形胚时期,四倍体组合的胚胎则基本全部解体。双受精胚囊内胚乳发育更为异常,在授粉后1d,游离胚乳核就开始解体退化,到授粉后3d不能形成细胞化胚乳或细胞化过程异常。与L202-2x作母本的杂交相比,以L202-4x作母本所得杂种胚胎发育更为滞后,且退化严重,形成的游离胚乳核少,解体早,不能进行细胞化。因此,利用同源四倍体栽培稻与药用野生稻杂交获得种间杂种的难度更大。

As maternal parents, diploid and autotetraploid plants of Oryza sativa cv. L202 were crossed with O. officihalls. Fertilization and embryo development in these two crosses were comparatively studied. There were no matured hybrid seeds obtained because all the hybridized spikelets died at 30 days after pollination （DAP）. The main reasons for non-seed set were abnormal fertilization and developments of the embryos and endosperms of interspecific hybrids. There were double fer tilization, egg cell single fertilization and non-fertilization in these crosses. Although 59.45 % and 54.87% hybrid embryos produced in the crosses of L202- 2x/O. officinalis and L202- 4x/O. officinalis, respectively, hybrid embryos ceased to develop or degenerated and plenty of free endosperm nuclei were in disaggregating state without developing cellular endosperms at 3 DAP. Otherwise, some embryological differences in these two crosses were found, that is, the rate of double fertilization and total rate of double and single fertilization in L202-3x/O. officinalis were higher than those in L202- 4x/0. officinalis. The embryo and endosperm of hybrids developed more slowly, and embryos and free endosperm nuclei were more severely degenerated in L202-4x/O. officinalis. Till 5 DAP, a few of embryos in L202-4x/O. of ficinalis developed into pear-shaped ones, however, embryos in L202-4x/O. officinalis were all degenerated. It was considered that obtaining interspecific hy brids by wide crosses between autotetraploid of O. sativa and O. officinalis was more difficult.