两对互补的显性基因控制着柑桔属和枳属的无融合生殖

Two Complementary Dominant Genes Controlling Apomixis in Genus Citrus and Poncirus

无融合生殖具有重要的学术价值和应用价值 ,这种生殖方式普遍存在于柑桔属及其近缘属植物中。对母本分别为单胚 (即有性生殖 )的宽皮柑桔品种克力迈丁和韦尔金、父本分别为多胚 (即无融合生殖 )的甜橙品种锦橙、新会橙、桃叶橙和哈姆林的杂种F1代群体总计 8个杂交组合的 2 2 9个开花结果后代 ,进行了胚性分离的调查 ,发现F1代中既有有性生殖 ,也有无融合生殖 ;有性生殖与无融合生殖的分离比例 ,在韦尔金后代中接近 1∶2 ,而在克力迈丁后代中接近 1∶1。根据该结果 ,结合前人的研究资料 ,提出在柑桔属和枳属或者还包括其他柑桔近缘属中 ,无融合生殖受到位于细胞核的两对互补的显性基因A1和A2的调控 ,且其中一对基因 ,设为A1表现显性纯合致死效应 ;两对基因的分离重组符合孟德尔的分离定律和自由组合定律。按该模式可以较为合理地解释已有的大部分常规杂交资料。

Apomixis is very common in Citrus genus and its rela te d genus. Two monoembryonic tangerine varieties (C. reticulata Blanco) Clemen tine and Wilking were used as seed parents to cross with four polyembryonic oran ge varieties [C. sinensis (L.) Osbeck]. Both sexual and apomictic progenie s were found in each F 1 population with different segregation ratios. In a tot al of 74 Wilking progenies, 23 were monoembryonic and 51 polyembryonic and the r atio of sexual and apomictic progenies was about 1∶2 tested either in each indi vidual cross or in the whole Wilking cross combionations. In Clementine progenie s, 84 were monoembryonic and 71 polyembryonic and the ratio was about 1∶1 teste d either in each individual cross or in the whole Clementine cross combionations . According to the results together with other data published, a possible apomix is controlling mechanism was proposed, which involves two complementary dominant genes named as A1 and - that control apomixis in genus Citrus and Poncirus. Trees of genotype A1 -- -, except for homozygous of domin ant gene A1 (which is lethal), can produce apomixis seeds. And those of othe r genotypes will produce sexual seeds. The segregation and recombination of thes e two genes accorded with Mendel's genetic laws. The proposed mechanism cou ld e xplain genotypes controlling polyembryonymonoembryony existing both in nature sp ecies and artificial hybridization progenies as well as most of the known hybrid ization results.