Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2007
Publication Date: 6/15/2008
Citation: Wada, S., Reed, B.M. 2008. Scarification and Germination Treatments Break Dormancy of Rubus Species. Meeting Abstract. p. 19. Interpretive Summary: The seeds of blackberry and raspberry have a deep dormancy the restricts germination. Rubus seeds are normally enclosed in a hard seedcoat that restricts germination and they usually exhibit delayed or poor germination. Wild species are important resources for breeding, but little is known about their germination requirements. In order to better define germination requirements we examined two ways of abrading the seed coat to improve germination. Concentrated sulfuric acid and sodium hypochlorite (bleach) were used to treat the seed of 6 species of wild blackberries and raspberries. After treatment, the seeds were germinated in the presence of water, or chemicals known to stimulate germination in other seed types. One species had 14.5% germination in the untreated seed, but untreated seed did not germinate at all for the other 5 species. At 6 months all sulfuric acid treatments produced 50 to 100 % germination for 5 of the species, but one had very low germination (2 to 9%) on all treatments. Sodium hypochlorite was less effective for all species. The best germination with sodium hypochlorite was 36% to 49%. Some of the individual chemical treatments were more effective for certain species than just the acid or base treatments alone.
Technical Abstract: The genus Rubus exhibits morphological diversity and a wide range of reproductive systems and habitats. Seeds of blackberry (subgenus Rubus) and raspberry (subg. Idaeobatus) have a deep dormancy caused by one or more mechanisms. Rubus seeds are normally enclosed in a hard schlerenchymatous endocarp that restricts germination. Seeds of Rubus species usually exhibit delayed or poor germination therefore causing substantial problems for breeders. Wild species are important resources for breeding, but little is known about their germination requirements. In order to better define germination requirements we examined the effect of two scarification agents, concentrated sulfuric acid (98% +), and sodium hypochlorite (14%), on the seed of 3 species in subg. Rubus; R. ursinus Cham. & Schltdl., R. georgicus Focke, R. caesius L. and 3 species in subg. Idaeobatus; R. hoffmeisterianus Kunth & C. D. Bouché, R. coreanus Miq., R. occidentalis L. After scarification seeds were germinated in the presence of water, GA3, GA3 + KNO3 or smoke treatments. R. caesius controls had 14.5% germination, but untreated seed did not germinate for the other 5 species. At 6 months sulfuric acid treatments produced 50 to 100 % germination for 5 of the species. R. occidentalis had very low germination (2 to 9%) on all treatments and reached a high of 9% with sulfuric acid and smoke. Sodium hypochlorite was less effective than sulfuric acid for all species. Germination with sodium hypochlorite was 36% for R. caesius, but with GA3 + KNO3 was 49%. R. hoffmeisterianus increased from 12% with sodium hypochlorite to 33% with GA3 + KNO3. When R. coreanus was treated with smoke we obtained 43% germination. Germination in Rubus often continues for an extended period so this study will continue for an additional 6 months.