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首页> 外文期刊>Mycologia >ELECTROPHORETIC KARYOTYPE POLYMORPHISMS IN THE GENUS PYTHIUM
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ELECTROPHORETIC KARYOTYPE POLYMORPHISMS IN THE GENUS PYTHIUM

机译：腐霉属的电泳核型多态性

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Inter- and intraspecific variation of the electrophoretic karyotypes of 18 Pythium spp. were evaluated by pulsed field gel electrophoresis. All species differed in karyotype, and while some morphologically similar species shared common ranges in chromosome size, this was not a consistent characteristic. Numbers of chromosomal bands for individual isolates ranged from seven to 20, while summation of their sizes ranged from 18.8 to 41.5 megabases. The extent of intraspecific variation was determined by examining 75 geographically diverse isolates representing 10 species. While there was general conservation in the size range of the chromosomes within a species, significant levels of intraspecific polymorphisms were identified. These differences were observed as variation in the number of chromosomal bands as well as summation of their sizes and differed by as much as 40% within a species. For most species differences in summation of chromosome sizes could be attributed to variation in the numbers of chromosomes present; however, for several species this also could be attributed to differences in the size distribution of the chromosomes. Depending on the species, rDNA was encoded on from one to five chromosomes, a feature that was generally conserved within a species. Karyotypes of P. myriolylum appeared to be mitotically stable with no apparent variation observed following repeated mycelial transfers over a period of a year. Meiotic stability of karyotypes was evaluated by selfing several homothallic species. For P. oligandrum, only one out of 28 S-1 progeny differed from the parent and this was due to the loss of a putative supernumerary chromosome. In contrast, while all 28 selfed progeny of P. spinosum were nearly identical to the parental karyotype, 61% differed in size or presence of at least one chromosomal band. Possible mechanisms responsible for this meiotic instability of P. spinosum and the observed level of intraspecific variation in the genus are discussed. In view of the levels of intraspecific polymorphism and meiotic instability of some isolates, analysis of electrophoretic karyotypes will have limited taxonomic utility. [References: 65]
机译：种间和种内变异的18个腐霉属的电泳核型。通过脉冲场凝胶电泳评估。所有物种的核型均不同，尽管某些形态相似的物种在染色体大小上具有相同的范围，但这并不是一致的特征。单个分离株的染色体条带数量范围为7至20，而其总和范围为18.8至41.5兆碱基。种内变异的程度是通过检查代表10种物种的75种地理上不同的菌株来确定的。虽然在一个物种中染色体的大小范围内有一般的保守性，但已鉴定出显着水平的种内多态性。观察到的这些差异是染色体条带数量的变化及其大小的总和，在一个物种内相差多达40％。对于大多数物种来说，染色体大小总和的差异可以归因于存在的染色体数目的变化。但是，对于某些物种，这也可以归因于染色体大小分布的差异。根据物种的不同，rDNA的编码范围为1至5条染色体，这一特征通常在物种内得以保留。 P. myriolylum的核型似乎是有丝分裂稳定的，在一年中反复进行菌丝体转移后未观察到明显的变化。核型的减数分裂稳定性是通过自交几种同型物种来评估的。对于寡头疟原虫，28个S-1后代中只有一个与亲本不同，这是由于丢失了一个假定的多余染色体。相比之下，尽管所有28个自旋多刺疟原虫的自交后代与亲本核型几乎相同，但是61％的大小或至少一个染色体带的存在不同。讨论了可能的机制，造成这种体育减数分裂不稳定和观察到的种内种内变异水平。考虑到某些分离株的种内多态性和减数分裂不稳定性的水平，电泳核型的分析在分类学上的应用将受到限制。 [参考：65]

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