Morphological, anatomical and photosynthetic consequences of artificial allopolyploidization in Cucumis

Studies have shown that polyploidy has pronounced effects on plants in multiple aspects, including genome structure, gene expression, metabolism and so on, which finally induce changes in phenotype. Many of these changes occurred immediately after polyploidization and retained or lost later. Therefore, it is meaningful for crop breeders to gain knowledge of these changes when it is relatively stable. In this study, we investigated the phenotypes of a highly self-pollinated synthesized allotetraploid in Cucumis, named with Cucumis × hytivus J. F. Chen & J. H. Kirkbr. (C. ×hytivus for short). Results showed that although many phenotypes of C. ×hytivus were intermediate between its parents, total leaf area and cell size exhibited parent-of-origin and dosage effect, respectively. Additionally, C. ×hytivus exhibited divergent biomass allocation strategy compared to the parents, developing more leaves. Beside the commonalities across different polyploid systems, the combination of hybridity and genome duplication in allopolyploids may lead to a diverse possibility of phenotypic changes. In spite of the reduced light absorption by less photosynthetic pigments in young leaves, allopolyploidy caused limited adverse effect on the photosynthesis of C. ×hytivus, which may benefit from the increased leaf thickness and potentially facilitated the survival and speciation of this novel species. The present study offers novel insights into the varied phenotypic effects of polyploidy and is a valuable reference for the crop improvement through polyploidization.