ABSTRACT

Pears (Pyrus spp.) mainly are divided into two main groups of Asian and European species with a wide diversity or similarity in fruit and morphological traits. In this study, flow cytometry was performed to evaluate the genome size of 37 cultivars and genotypes of Asian, European, and Iranian indigenous pears. Besides, the relationship between cytological and morphological traits was investigated for the first time. Morphological traits were measured based on the International Union for the Protection of New Varieties of Plants (UPOV) descriptor. There were positive relationships between genome size, the fruit pedicel length, and the length to fruit diameter ratio. Although, as the genome size was increased, the fruit diameter and size were decreased. Increasing 1.6 pg of the genome size causes a reduction of one cm in the pear fruit diameter. Moreover, with a larger genome size by 1.1 pg, there was an increase in fruit pedicel by one cm. The obtained results revealed that most of the Iranian native genotypes were similar in shape to European pears, but some of them were also oriented to Asian pear cultivars. Most studied cultivars originated between different regions were diploid (2n = 34) and their genome size varied between 0.99 and 1.99 pg. The average genome size of European and Iranian pears was 1.29 pg and Asian’s was 1.32 pg. The principal component analysis (PCA) result showed that the Asian and European genotypes were distinctly separated. Also, according to the cluster analysis, the indigenous cultivars of Iran can be located in the European pear group species. There was a relationship between the East Asian and European pear origins because of the possible gene flow between two major pear culture regions in the past. In general, Iran can be considered as an important region and pathway of gene flow transfer and a rich center of genetic variation of pears. Therefore, this study provided essential information and a useful tool for genetic diversity or similarity assessment of pears through genome size and some morphological traits prediction. Further research on wider fruit tree species in the different fruit-growing regions of the world will warrant the use of genome size as a novel prediction tool for the important morphological traits with specific commercial breeding objectives.

摘要

梨（梨spp。）主要分为亚洲和欧洲两个主要种类，其果实和形态特征具有广泛的多样性或相似性。在这项研究中，进行了流式细胞术以评估37个品种的基因组大小以及亚洲，欧洲和伊朗土著梨的基因型。此外，首次研究了细胞学与形态性状之间的关系。根据国际植物新品种保护联盟（UPOV）描述符对形态特征进行了测量。基因组大小，果实梗长度和长度与果实直径之比之间存在正相关关系。尽管随着基因组大小的增加，果实的直径和大小减小了。基因组大小增加1.6 pg会导致梨果实直径减小1厘米。而且，当基因组大小增加1.1 pg时，果梗增加了1 cm。获得的结果表明，大多数伊朗本土基因型在形状上与欧洲梨相似，但其中一些也与亚洲梨品种有关。大多数研究的起源于不同区域之间的品种是二倍体（2n = 34），它们的基因组大小在0.99和1.99 pg之间变化。欧洲和伊朗梨的平均基因组大小为1.29 pg，亚洲梨为1.32 pg。主成分分析（PCA）结果表明，亚洲和欧洲的基因型是明显分开的。同样，根据聚类分析，伊朗的本地品种可以位于欧洲梨类物种中。由于过去两个主要梨文化产区之间可能存在基因流，因此东亚和欧洲梨的起源之间存在联系。总的来说，伊朗可以被视为重要的基因流转移地区和途径，也是梨遗传变异的重要中心。因此，这项研究为通过基因组大小和某些形态特征预测梨的遗传多样性或相似性评估提供了必要的信息和有用的工具。在世界不同水果种植地区，对更广泛的果树种类的进一步研究将保证将基因组大小用作具有特定商业育种目的的重要形态性状的新型预测工具。伊朗可以被认为是基因流转移的重要地区和途径，也是梨遗传变异的丰富中心。因此，这项研究为通过基因组大小和某些形态特征预测梨的遗传多样性或相似性评估提供了必要的信息和有用的工具。在世界不同水果种植地区，对更广泛的果树种类的进一步研究将保证将基因组大小用作具有特定商业育种目的的重要形态性状的新型预测工具。伊朗可以被认为是基因流转移的重要地区和途径，也是梨遗传变异的丰富中心。因此，这项研究为通过基因组大小和某些形态特征预测梨的遗传多样性或相似性评估提供了必要的信息和有用的工具。在世界不同水果种植地区，对更广泛的果树种类的进一步研究将保证将基因组大小用作具有特定商业育种目的的重要形态性状的新型预测工具。