Seed Coat Morphology Differentiates Blackberry Cultivars

Abstract

Determining the cultivar identity of blackberry ( RubusL.) fruit may be problematic when the parent plant is not available for examination. The ability to correctly identify commercial cultivars is important to the industry. Less desirable cultivars may be mistaken or substituted for more desirable ones, resulting in mislabeled products or economic losses. The objective of this study was to develop a simple and effective method to distinguish blackberry cultivars using seed morphology. Seeds of 17 commercially important blackberry cultivars (‘Black Diamond’, ‘Black Pearl’, ‘Boysen’, ‘Cacanska Bestrna’, ‘Chester Thornless’, ‘Hull Thornless’, ‘Kotata’, ‘Loch Ness’, ‘Marion’, ‘Navaho’, ‘Nightfall’, ‘Obsidian’, ‘Newberry’, ‘Silvan’, ‘Tupy’, ‘Wild Treasure’, and ‘Young’) were collected from the United States Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR) and Horticultural Crops Research Laboratory (HCRL), Corvallis, Oregon. Seeds were examined with a dissecting light microscope and scanning electron microscopy. A key characteristic was the shape of the raphe on the seed: straight, concave or convex. The 17 cultivars could be divided into three groups based on raphe shape. Cultivars within each group could be differentiated by seed shape, size, color and seed-coat sculpturing. Cultivars originating from the same parents (full sibs) or the same maternal line could be distinguished as well. Although scanning electron microscopy showed the seed coat sculpturing in greater detail, all cultivars could be distinguished successfully using a dissecting microscope.