Department of Applied Biology, Research Institute of Horticulture, Konstytucji 3 Maja 1/3 Street, 96-100 Skierniewice, Poland.
Department of Phytopathology, Research Institute of Horticulture, Konstytucji 3 Maja 1/3 Street, 96-100 Skierniewice, Poland.
Int J Mol Sci. 2021 Jan 7;22(2):527. doi: 10.3390/ijms22020527.
Among the fungal diseases of apple trees, serious yield losses are due to an apple scab caused by . Protection against this disease is based mainly on chemical treatments, which are currently very limited. Therefore, it is extremely important to introduce cultivars with reduced susceptibility to this pathogen. One of the important sources of variability for breeding is the process of polyploidization. Newly obtained polyploids may acquire new features, including increased resistance to diseases. In our earlier studies, numerous tetraploids have been obtained for several apple cultivars with 'Free Redstar' tetraploids manifesting enhanced resistance to apple scab. In the present study, tetraploids of 'Free Redstar' were assessed in terms of phenotype and genotype with particular emphasis on the genetic background of their increased resistance to apple scab. Compared to diploid plants, tetraploids (own-rooted plants) were characterized with poor growth, especially during first growing season. They had considerably shorter shoots, fewer branches, smaller stem diameter, and reshaped leaves. In contrast to own-rooted plants, in M9-grafted three-year old trees, no significant differences between diplo- and tetraploids were observed, either in morphological or physiological parameters, with the exceptions of the increased leaf thickness and chlorophyll content recorded in tetraploids. Significant differences between sibling tetraploid clones were recorded, particularly in leaf shape and some physiological parameters. The amplified fragment length polymorphism (AFLP) analysis confirmed genetic polymorphism of tetraploid clones. Methylation-sensitive amplification polymorphism (MSAP) analysis showed that the level of DNA methylation was twice as high in young tetraploid plants as in a diploid donor tree, which may explain the weaker vigour of neotetraploids in the early period of their growth in the juvenile phase. Molecular analysis showed that 'Free Redstar' cultivar and their tetraploids bear six genes (, , , , and ). Transcriptome analysis confirmed enhanced resistance to apple scab of 'Free Redstar' tetraploids since the expression levels of genes related to resistance were strongly enhanced in tetraploids compared to their diploid counterparts.
在苹果树的真菌病害中，严重的产量损失是由苹果黑星病引起的。这种疾病的防治主要基于化学处理，但目前这种方法非常有限。因此，引入对这种病原体敏感性降低的品种是非常重要的。育种的一个重要变异来源是多倍化过程。新获得的多倍体可能会获得新的特征，包括增加对疾病的抵抗力。在我们之前的研究中，已经为几个苹果品种获得了许多四倍体，其中“自由红星”四倍体表现出对苹果黑星病的增强抗性。在本研究中，评估了“自由红星”四倍体的表型和基因型，特别强调了其对苹果黑星病增强抗性的遗传背景。与二倍体植物相比，四倍体（自根植物）的生长较差，特别是在第一个生长季节。它们的枝条短、分枝少、茎径小、叶片变形。与自根植物不同，在 M9 嫁接的三年生树上，无论是在形态还是生理参数方面，二倍体和四倍体之间都没有观察到显著差异，除了四倍体记录的叶片厚度和叶绿素含量增加。在四倍体克隆之间记录了显著的差异，特别是在叶片形状和一些生理参数方面。扩增片段长度多态性（AFLP）分析证实了四倍体克隆的遗传多态性。甲基化敏感扩增多态性（MSAP）分析表明，年轻四倍体植物的 DNA 甲基化水平是二倍体供体树的两倍，这可能解释了在幼年期生长的早期阶段新四倍体活力较弱的原因。分子分析表明，“自由红星”品种及其四倍体携带六个 基因（、、、、和 ）。转录组分析证实了“自由红星”四倍体对苹果黑星病的增强抗性，因为与抗性相关的基因在四倍体中的表达水平明显高于二倍体。
