Genetic analysis of apomixis in Citrus and Poncirus by molecular markers
Genetic analysis of apomixis in Citrus and Poncirus by molecular markers
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DOI：
10.1007/s001220051264
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发表时间：
1999-08-01
影响因子：
5.4
通讯作者：
Carbonell, EA
中科院分区：
文献类型：
--
作者：
García, R;Asíns, MJ;Carbonell, EA
柑桔砧木的繁殖依赖于由心心幼苗产生无性系植株。这使得无融合性成为柑桔砧木育种中的重要性状之一。研究了一株50树的无融合生殖后代的遗传控制。利用69个分子标记对三叶草进行分离分析。采用同工酶分析方法，每棵树连续栽培2年25株，估算出珠心苗的比例。还确定了果树的胚胎类型（多胚与单胚种子）。每个亲本物种的单独遗传图谱被开发出来。这些图谱的整合和比较可以利用共同的多等位基因分离位点来完成。结果表明，两种物种特异性遗传图谱在基因同源性上存在差异。在一些基因组区域，特别是花粉亲本，已经观察到标记分离的重要扭曲，其中一些还涉及c -甲基化模式的差异。数量性状位点（qtl）分析显示，有6个基因组位点（在三叶松中有2个，在美洲松中有4个）分别占无融合变异总变异的24%。在同一物种中，即使在同一连锁组中，也存在正等位基因和负等位基因效应的qtl。其中一个与无融合相关的标记（Apo2）也与胚胎类型相关。因此，与配子体无融合生殖的遗传控制相比，柑橘无融合生殖（珠心胚）的遗传控制非常复杂。与无杂交控制qtl相关的分子标记将有助于柑橘品种无杂交砧木的选择。
Propagation of citrus rootstocks depends upon the production of clonal plants from nucellar seedlings. This makes apomixis one of the host important traits in breeding programs for citrus rootstocks. The genetic control of apomixis was studied in a 50-tree progeny derived from the cross C. volkamerianaxP. trifoliata using 69 molecular markers and bulked segregant analysis. The proportion of nucellar seedlings was estimated by isoenzymatic analysis of 25 seedlings per tree for 2 consecutive years. The type of embryony (polyembryonic versus monoembryonic seeds) was also determined for fruit-yielding trees. Separate genetic maps for each parental species were developed. The integration and comparison of these maps could be accomplished using common multiallelic segregant loci. Differences in gene synteny between the two species-specific genetic maps were shown. Important distortions in the segregation of markers at several genomic regions, some of them also involving differences in the C-methylation pattern, have been observed, especially for the pollen parent. Analysis of quantitative trait loci (QTLs) revealed the presence of six genomic positions (two in P. trifoliata and four in C. volkameriana) contributing individually up to 24% of the total variation for apomixis. Within the same species, QTLs with positive and negative allele effects were present, even in the same linkage group. One of the markers associated to apomixis (Apo2) is also associated to embryony type. Therefore, the genetic control of apomictic reproduction found in citrus (nucellar embryony) is quite complex compared to what has been reported for gametophytic apomixis. Molecular markers linked to QTLs governing apomixis will be useful to assist selection of future apomictic rootstocks for citrus varieties.