Allopolyploid wheat (Triticum aestivum L.) carries three pairs of homoeologous genomes but its meiotic pairing is diploid‐like. This is the effect of the Ph (pairing homoeologous) system which restricts chromosome pairing to strictly homologous. Ph1 is the locus with the strongest effect. Disabling Ph1 permits pairing between homoeologues and is routinely used in chromosome engineering to introgress alien variation into breeding stocks. Whereas the efficiency of Ph1 and the general pattern of homoeologous crossovers in its absence are quite well known from numerous studies, other characteristics of such crossovers remain unknown. This study analyzed the crossover points in four sets of the ph1b‐induced recombinants between wheat homologues as well as between three wheat and rye (Secale cereale) homoeologous chromosome arms, and compared them to crossovers between homologues in a reference wheat population. The results show the Ph1 locus also controls crossing over of homologues, and the general patterns of homologous (with Ph1) and homoeologous (with ph1b) crossing over are the same. In all intervals analyzed, homoeologous crossovers fell within the range of frequency distribution of homologous crossovers among individual families of the reference population. No specific DNA sequence characteristics were identified that could be recognized by the Ph1 locus; the only difference between homologous and homoeologous crossing over appears to be in frequency. It is concluded that the Ph1 locus likely recognizes DNA sequence similarity; crossing over is permitted between very similar sequences. In the absence of Ph1 dissimilarities are ignored, in proportion to the level of the sequence divergence.

中文翻译：

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小麦与黑麦染色体诱导重组中交叉的一些特征

异源多倍体小麦（Triticum aestivum L. ）携带三对同源基因组，但其减数分裂配对是二倍体样的。这是Ph（配对同源）系统的影响，它将染色体配对限制为严格同源。Ph1是影响最强的基因座。禁用Ph1允许同源物之间的配对，并且通常用于染色体工程以将外来变异渗入繁殖种群。尽管Ph1的效率和没有它的同源交叉的一般模式在许多研究中是众所周知的，但这种交叉的其他特征仍然未知。本研究分析了四组ph1b 中的交叉点诱导重组小麦同源物之间以及三个小麦和黑麦（黑麦）同源染色体臂之间，并将它们与参考小麦群体中同源物之间的交叉进行比较。结果表明Ph1基因座也控制同源物的交叉，同源（与Ph1）和同源（与ph1b）交叉的一般模式是相同的。在所有分析的区间中，同源交叉落在参考种群个体家庭之间同源交叉的频率分布范围内。没有鉴定出可以被Ph1识别的特定 DNA 序列特征轨迹; 同源和同源交叉之间的唯一区别似乎是频率。得出的结论是，Ph1基因座可能识别 DNA 序列相似性；在非常相似的序列之间允许交叉。在没有Ph1的情况下，与序列差异的水平成正比的差异被忽略。