湖北海棠无融合生殖遗传分析与胚发育模式研究

Genetic Analysis of Apomixis and Development Pattern of Embryo of Malus hupehensis Rehd.

以湖北海棠变种平邑甜茶、泰山海棠与B9做杂交组合,培育实生苗1 477株,筛选杂种F1代96株。用去雄套袋法鉴定F1的无融合生殖率,用流式细胞仪鉴定杂种的染色体倍性。结果表明,无融合生殖型率在80%以上的有40株,15%以下有40株,20%~50%之间有16株;25株四倍体皆为无融合生殖型,10株二倍体皆为有性生殖型,三倍体中无融合生殖型加上中间型与有性生殖型数量比接近1∶1。初步推测湖北海棠的无融合生殖基因型为“Aaa”（“A”显性,无融合生殖;“a”隐性,有性生殖）,以显性单基因质量性状为主,也有数量性状效应;胚囊多数情况下由未减数的2n=3x配子直接发育成与母株基因相同的胚,部分2n配子与雄配子结合,形成2n＋n=4x型后代,少量胚囊经减数分裂产生n=x、n=2x两种配子,无融合生殖基因随n=2x配子分离。

The crossings were made between Malus hupehensis, var. pingyiensis, Malus hupehensis, var. taishanensis and B9. The 96 F1 hybrids were selected from the population of 1 477. The emasculated flowers were bagged to identify the apo- mictic ratio. The flow cytometry was used to identify the chromosome ploidy of seedlings. Results showed that the 40 hybrids seedlings were at over 80% of apo-mictic ratios, other 40 seedlings were at below 15%, the 16 hybrids were at 20% to 50%. All of 25 tetraploids were apomictic seedlings, and all of 10 diploids were sexual seedlings, the ratio of the apomictic type plus intermediate type to the sexual type were close to 1 ： 1 in the triploids. The studies suggested that the genotype of apomixis in Malus hupehensis could be ‘Aaa＇‘A＇ represented a dominant type to give apomixis and ‘a’ represented a recessive type to give sexual propagation. The apomixis was controlled mainly by major genes, and also affected by some minor genes. Most of the megaspores could directly developed into an embryo from a ‘2n =3x’ unreduced gamete, resulting in the same genotype as their maternal tree. Some of the ‘2n’ gametes could combine with a male gamete to form a 4x genotype （2n＋n= 4x）. Few megaspores might segregate into two types of gametes, that were ‘n=x＇ and ‘n=2x＇, and the apomixis gene could be segregated with the ‘n= 2x’ gametes.