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ARS Home » Pacific West Area » Corvallis, Oregon » National Clonal Germplasm Repository » Research » Publications at this Location » Publication #203662
Title: Morphological Analysis of Rubus Seed

Author
item WADA, SUGAE - OREGON STATE UNIVERSITY
item Reed, Barbara

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2007
Publication Date: 1/20/2008
Citation: Wada, S., Reed, B.M. 2008. Morphological Analysis of Rubus Seed. Acta Horticulturae. (782)p. 67-74.

Interpretive Summary: Raspberries and blackberries are widely diverse plants with a range of reproductive systems and habitats. The seeds of blackberry and raspberry become dormant when dried and are difficult to germinate. Seed coat structures provide crucial clues for encouraging germination. We examined seed coat structures with the scanning electron microscope. Photographs were taken of 38 samples of seeds collected worldwide. The results showed some clear trends in sculpture pattern of the seed coat. Similar patterns occurred in most of the subgroups but two subgroups showed a dramatic pattern of surface relief of the outer cell walls. Species belonging to one group had significant and steeper-edged ridges while the other group had smoothly curved rounded ridges. One sub group showed a smooth, finely textured surface with no significant ridges. Accessions of one group from three geographical regions had a consistent pattern regardless of origin. These surface seed characteristics provide useful information to identify raspberry and blackberry subgroups.

Technical Abstract: The genus Rubus exhibits morphological diversity and a wide range of reproductive systems and habitats. We examined seed coat ultrastructural morphology of seed accessions of 10 subgenera preserved at the US Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Oregon, using scanning electron microscopy (SEM). SEM images were taken of 56 seed samples collected worldwide. Macromorphological characteristics differed among groups at the subgenus level, Chamaemorus, Cyclactis (except R. saxatilis L.), Idaeobatus, Lampobatus, Malachobatus, and Michranthobatus have similar exomorphic patterns. R. odoratus L. and R. parviflorus Nutt. (subg. Anoplobatus) had a unique hilar end hole. R. saxatilis had seed coat sculpturing inconsistent with its assigned subgenus (subg. Cyclactis) and more in common with subg. Idaeobatus. The subgenera Rubus and Idaeobatus showed conspicuous patterns of reticulate and rugose surface relief of the outer cell walls. Species belonging to the subgenus Rubus had steeper-edged truncate or acute lateral ridges with a wide and protruded raphal region, while Idaeobatus had smoothly curved rounded ridges and raphal region. The two species in subgenus Chamaemorus showed areticulate, finely textured surface with flat or no secondary cell wall protrusion and a ridged raphe. The subgenera Anoplobatus, Malachobatus and Michranthobatus had similar sculpturing. For R. arcticus L., subgenus Cyclactis, accessions from three geographical regions had a consistent microsculpture patterns. These morphological characteristics of Rubus seed revealed by SEM provide additional information to identify infraspecific levels of the genus Rubus.