Phenotypic analysis of polyploid and aneuploid haskap plants and their progeny production

The relationship between the ploidy level and phenotype in haskap (Lonicera caerulea L. subsp. edulis (Turcz. ex Herder) Hultén) is mostly unclear. Therefore, this study investigated the fruit and leaf phenotypes of diploid, tetraploid, pentaploid, hexaploid, and aneuploid (2n = 6x - 3) haskap plants. A concomitant positive increase in the ploidy level was observed between diploids and tetraploids in fresh fruit weight and size, but this trend was not observed in higher-order ploidy levels above pentaploids. The same tendency was observed in the soluble solids content of the fruit. No relationship was found among the other traits with ploidy levels. Therefore, in the phenotype of haskap plants, the trend accompanying the change in ploidy level may differ between individuals below tetraploid and above pentaploid, and the influence of genotype is probably greater than that of ploidy levels. Generally, higher-order polyploid plants have low fertility, especially plants with odd ploidy, and the production of progeny is difficult. In this study, seeds of higher-order ploidy haskap plants demonstrated their ability to germinate and grow. Furthermore, the progeny of these hyperploid lineages showed polyploidy or aneuploidy between tetraploidy and hexaploidy. This study focuses on the higher-order polyploid haskap plants and discusses the genetic findings, such as the phenotype, fertility, and ploidy of the progeny, obtained from these plants. This study will provide basic information on breeding by using polyploid plants.