The first report of an alloheptaploid from the genus Fragaria (Rosaceae)

Abstract

Abstract Hybrid recognition in the genus Fragaria (strawberry, Rosaceae) is difficult when based on morphological characteristics since there is great similarity among Fragaria species, even between different ploidy levels. This study aimed to identify and characterise an alloheptaploid hybrid (2n = 7x = 49) Fragaria for the first time in the genus from Europe (Germany, Bavaria) using different techniques. The hybrid was documented based on the evidence obtained from ploidy levels using flow cytometric measurement of nuclear DNA content, identification of the parental origin using 14 RAPD primers, fertility assessment from artificial crosses and fruit set level. RAPD analysis showed that the hybrid shared five species-specific markers with diploid F. vesca, and three with hexaploid F. moschata, indicating these species to be the most likely parents. The mean fluorescent intensity reflected by nuclear DNA in the putative hybrid (703) fell within the range accepted for heptaploidy in Fragaria, while the corresponding values for the putative parental species were 232 and 622. We concluded that an unreduced gamete from F. moschata and a normal gamete of F. vesca were involved in the formation of this hybrid. The hybrid produced 15 flowers during a period of over 2·5 years in the glasshouse, of which four set berries. Six flowers of the putative hybrid when hand-pollinated with pollen of F. moschata produced five berries. This study shows that allopolyploidy is still active in the evolution and speciation of the genus Fragaria.