Department of Plant Breeding and Genetics, PMAS-Arid Agriculture University Rawalpindi, Rawalpindi, Pakistan.
Department of Plant Breeding and Genetics, University of Agriculture Faisalabad, Faisalabad, Pakistan.
Mol Biol Rep. 2022 Jun;49(6):5511-5520. doi: 10.1007/s11033-022-07431-z. Epub 2022 Apr 28.
Onion is an economically important vegetable cultivated worldwide on a large scale. Liberal exchange of germplasm and frequent selection caused narrow genetic diversity in most crops, including onion. Thus, it is essential to estimate and understand genetic diversity before launching of any breeding program. The current study was conducted to explore genetic diversity among 39 short-day onion genotypes (indigenous and exotic).
All the genotypes were evaluated for various phenotypic traits by using single nucleotide polymorphism (SNP) genotyping based on KASPar assays. Principal component analysis (PCA) was performed to determine the variability among genotypes. The four principal components with eigenvalue greater than 1 accounted for 67.5656% variability for quantitative traits, whereas first five principal components with eigenvalue greater than 0.7 accounted for 86.24% variation among the genotypes for qualitative traits. The principal component analysis identified diverse traits including bulb weight, bulb diameter, plant height, number of survived plants and vitamin C. These traits were further analyzed through ANOVA (Analysis of Variance) following augmented block design to describe genotypic variability for selected traits. Onion genotypes showed significant variation for bulb weight, bulb diameter and Vitamin C. Genotypic clustering based on PCA showed that 15 indigenous genotypes were clustered with exotic genotypes (14) while remaining indigenous genotypes (10) were distant. A total of 30 SNPs were used for assessment of genetic diversity out of these, 24 SNPs were detected with polymorphic loci (0.8%, heterozygosity), while only six markers were with monomorphic sites (0.2% heterozygosity). Subsequently, population structure analysis revealed three different populations indicating significant variability.
Conclusively, a significant similarity between exotic and a group of indigenous genotypes indicates direct adoption of exotic genotypes or their sister lines. A further broadening of the genetic base is required and could be done by crossing distant genotypes.
洋葱是一种在全球范围内大规模种植的经济重要蔬菜。自由的种质交流和频繁的选择导致大多数作物，包括洋葱，遗传多样性狭窄。因此，在启动任何育种计划之前，估计和了解遗传多样性是至关重要的。本研究旨在探索 39 个短日照洋葱基因型（本地和外来）之间的遗传多样性。
所有基因型均通过基于 KASPar 测定的单核苷酸多态性（SNP）基因分型评估各种表型性状。进行主成分分析（PCA）以确定基因型之间的变异性。具有特征值大于 1 的前四个主成分占数量性状变异性的 67.5656%，而具有特征值大于 0.7 的前五个主成分占定性性状中基因型变异的 86.24%。主成分分析确定了包括鳞茎重量、鳞茎直径、株高、存活植株数和维生素 C 在内的多种性状。这些性状通过增广块设计的方差分析（ANOVA）进一步分析，以描述所选性状的基因型变异性。洋葱基因型在鳞茎重量、鳞茎直径和维生素 C 方面表现出显著差异。基于 PCA 的基因型聚类表明，15 个本地基因型与外来基因型（14 个）聚类，而其余本地基因型（10 个）较远。总共 30 个 SNP 用于遗传多样性评估，其中 24 个 SNP 在多态性位点（0.8%，杂合性）中检测到，只有 6 个标记在单态性位点（0.2%杂合性）中检测到。随后，群体结构分析显示存在三个不同的群体，表明存在显著的变异性。
外来和一组本地基因型之间的显著相似性表明直接采用外来基因型或其姐妹系。需要进一步扩大遗传基础，可以通过杂交远缘基因型来实现。
