Summary Karyotype analyses have been useful for clarifying phylogenetic and evolutionary relationships among related species and sub-specific taxa. Within the 22 wild species in the genus Fragaria (Rosaceae), karyotype analyses had been restricted to diploid species. The objectives of this research were to determine the chromosomal morphology and analyze the karyotypes of wild octoploid and decaploid species within this genus.
Strawberry (Fragaria × ananassa) contains a major allergen, Fra a 1, which causes oral allergic syndrome. Fra a 1 is a PR-10 homolog that is regulated by environmental conditions. The allergenicity of fruit caused by Fra a 1 may depend on the genotype or growing conditions. We analyzed the Fra a 1.01 transcript levels and Fra a 1.01 protein levels in strawberry fruits of several genotypes across all seasons. In the preliminary rough screening, we selected the line WH1 bearing white fruit and the red-fruited cultivar 'Akihime'. Under the same environmental conditions, there was no significant difference in Fra a 1.01 levels between the two cultivars over several months, suggesting that receptacle color was not indicative of allergenicity caused by Fra a 1.01. Fruits cultivated under the same environmental conditions should be used for comparisons of the allergenicity among genotypes. Both 'Akihime' and WH1 accumulated significantly higher levels of Fra a 1.01 protein in winter than in spring. We investigated the effects of irradiation and low temperature as environmental factors controlling the accumulation of Fra a 1.01 in winter. A shading treatment on fruit did not significantly affect Fra a 1.01 protein accumulation in strawberry fruits. Regarding variations over time, the Fra a 1.01 protein content was higher in fruits harvested at midnight in January than in those harvested at other times and in other months. These findings suggested that the Fra a 1.01 protein accumulates in response to environmental factors such as cold stress.
SummaryThe strawberry, genus Fragaria (Rosaceae), has a basic chromosome of xϭ7, and is comprised of 20 wild species having an euploid series from diploid (2nϭ2xϭ14) through decaploid (2nϭ10xϭ70). Few karyotypes of species in this genus have been reported. The objective of this research was to determine the chromosomal morphology and karyotype analysis of wild diploid, tetraploid and hexaploid Fragaria species. Somatic chromosome images of 20 genotypes of diploids, tetraploids, and hexaploids were taken at the metaphase stage of mitosis under a light microscope. Karyotype analysis was performed in 17 accessions. The phylogenetic relationships between species were constructed using cluster analysis based on karyotypic similarity. Somatic chromosome numbers of wild diploid, tetraploid and hexaploid species were 2nϭ2xϭ14, 2nϭ4xϭ28 and 2nϭ 6xϭ42. Chromosome morphology in wild diploid species had greater uniformity than that in the tetraploid species. Results of the cluster analysis showed that the diploid and tetraploid species reside in separate clades, with one exception. Fragaria tibetica, a tetraploid, clustered with the diploid species clade. The hexaploid, F. moschata, clustered with the tetraploid species clade.
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