The genus Vitis contains two subgenera, Euvitis (bunch grapes) and Muscadinia (muscadine grapes). The muscadine grape, Vitis rotundifolia Michx., is the only commonly cultivated member of the Muscadinia subgenus. Muscadine grapes are native to the southern United States and have been cultivated for over 400 years. The muscadine grape differs from the familiar bunch grape (Vitis labrusca, V. vinifera, and their various hybrids) in several morphological characteristics, including that they have smaller clusters, the berries abscise from the cluster (shatter) at maturity, the tendrils are unbranched, and the berries have thick skins and a unique fruity aroma.
The University of Georgia has been breeding muscadine grapes for nearly 100 years and routinely germinates large seedling populations. In the only published study on muscadine seed germination to our knowledge, Nesbitt et al. (1976) found that germination rates in excess of 90% could be obtained by cold-stratifying seed in moist sand for 80 to 100 d before planting. Unfortunately, we are unable to replicate those results, and the breeding program has been hampered by erratic germination timings and low germination rates of muscadine seed.
Barriers to germination have been better studied in Euvitis grapes, and these studies provide a starting point to investigations into muscadine seed germination. Euvitis seed generally has very low germination rates until endodormancy has been removed (Ellis et al., 1983). Dormancy removal is generally achieved by cold-stratification of the seeds for a period of 3 to 4 months (Einsett and Pratt, 1975), but in many varieties, this results in only modest germination rates (Ellis et al., 1983; Scott and Ink, 1950; Selim et al., 1981). Grape seeds have a thick, tough seedcoat that can be a mechanical barrier to germination. Attempts at scarifying seeds with sulfuric acid provided minimal benefits and was harmful to seed viability if not handled carefully (ChiaWei and ShyiKuan, 2003; Scott and Ink, 1950); however, Ramirez (1968) found that nicking seeds during extraction with a blender blade was beneficial to germination. Treatment of grape seeds with gibberellic acid (GA3) before stratification has generally been found to promote germination (Kachru et al., 1972; Pal et al., 1976; Selim et al., 1981; Yeou-Der et al., 1967). Ellis et al. (1983) found that the effect of the GA3 could be improved by an additional pretreatment in 0.5 M hydrogen peroxide (H2O2) before the GA3 pretreatment. In addition, an alternating germination temperature of 30/20 °C with the higher temperature being applied for 8 h every 24 h was superior to a single germination temperature. Kachru et al. (1972) attribute grape seed dormancy to a water-soluble inhibitor, most likely abscisic acid, which can be removed with leaching by running water.
The goal of this study was to test various seed treatments in an attempt to improve overall germination rates of muscadine seed and lower the lengthy stratification periods now used.
ChiaWei, S. & ShyiKuan, O. 2003 Improving seed germination of ‘Kyoho’ grape by treatments of gibberellic acid, leaching, scarification, and stratification J. Agr. Res. China 52 14 22
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Ellis, R.H., Hong, T.D. & Roberts, E.H. 1983 A note on the development of a practical procedure for promoting the germination of dormant seed of grape (Vitis spp.) Vitis 22 211 219
Kachru, R.B., Singh, R.N. & Yadav, I.S. 1972 Physiological studies on dormancy in grape seeds (Vitis vinifera var. Black Muscat) Vitis 11 289 295
Nesbitt, W.B., Earp, J.B. & Kirk, H.J. 1976 After ripening and stratification of Vitis rotundifolia seed improves germination HortScience 11 38 (abstr.)
Ogawa, K. & Iwabuchi, M. 2001 A mechanism for promoting the gercmination of Zinnia elegans seeds hydrogen peroxide Plant and Cell Phys. 42 286 291
Pal, R.N., Singh, R., Vij, V.K. & Sharma, J.N. 1976 Effect of gibberellins GA3, GA4/7, and GA13 on seed germination and subsequent seedling growth in Early Muscat grape (Vitis vinifera) Vitis 14 265 268
Ramirez, O.C. 1968 Comparative embryogenesis of Erie, Concord, and Golden Muscat grape varieties as related to the germinability of seeds Rutgers University Brunswick, NJ. PhD Diss. Abstr 29 1230 B
Selim, H.H., Ibrahim, F.A., Fayek, M.A., El-Deen, S.A. & Gamal, N.M. 1981 Effect of different treatments on germination of Romi red grape seeds Vitis 20 115 121
Yeou-Der, K., Weaver, R.J. & Pool, R.M. 1967 Effect of low-temperature and growth regulators on germination of seeds of ‘Tokay’ grapes J. Amer. Soc. Hort. Sci. 92 323 330