2018 ASHS Annual Conference

Native to eastern regions in North America, the genus Aronia is a group of deciduous shrubs in the Rosaceae family, subtribe Pyrinae. The four commonly accepted species include A. arbutifolia (L.) Pers., red chokeberry; A. melanocarpa (Michx.) Elliott, black chokeberry; A. prunifolia (Marshall) Reheder, purple chokeberry; and A. mitschurinii (A.K. Skvortsov & Maitul), involving A. melanocarpa × Sorbus aucuparia hybridization. Very little has been accomplished with genetic improvement of polyploid Aronia genotypes due to the suspected apomictic reproductive mechanisms in this genus. The objectives of this study were: 1) elucidate the reproductive mechanisms of Aronia species and reveal the occurrence of apomixis within the genus and 2) determine the genetic diversity of commercial cultivars of A. mitschurinii. For experiment I, 20 Aronia accessions (five A. melanocarpa [2x], four A. melanocarpa [4x], three A. prunifolia [3x], four A. prunifolia [4x], three A. arbutifolia [4x], one A. mitschurinii [4x]) were used in this study. Intra-accession variability was evaluated by growing out progeny from an open-pollinated maternal accession and comparing Amplified Fragment Length Polymorphism (AFLP) profiles between the progeny and maternal accession. Diploid accessions produced a significant amount of genetic variation (0.6-0.8 Jaccard’s similarity coefficient) in progeny which was indicative of sexual reproduction. Seedlings from tetraploid accessions had very little genetic variation (0.90-0.98 Jaccard’s similarity coefficient) in comparison to their maternal accession. The very limited genetic variation observed in tetraploid progeny suggests that apomictic diplospory with one round of meiotic division is occurring. Triploid accessions appear to reproduce via sexual reproduction and apomictic diplospory. For experiment II, genetic similarities were determined for nine A. mitschurinii cultivars that are commonly used in commercial fruit production. All cultivars, except for ‘Nero’, were genetically identical, with ‘Nero’ producing a Jaccard’s similarity coefficient of 0.97. We propose that the same genotype has been renamed repeatedly by growers. Nero is likely a seedling of the primary clone in commerce, since it has a similarity coefficient that is equivalent to what we observed in tetraploid Aronia progeny.