Somaclonal Variation among ex vitro `Thornless Evergreen' Trailing Blackberries: The Morphological Status of Selected Clones after Seven Years of Field Growth

in Journal of the American Society for Horticultural Science
Authors:
M.A. NortonUniversity of Illinois, Department of Natural Resources and Environmental Sciences, 258 Madigan Laboratory, 1201 West Gregory Drive, Urbana, IL 61801

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R.M. SkirvinUniversity of Illinois, Department of Natural Resources and Environmental Sciences, 258 Madigan Laboratory, 1201 West Gregory Drive, Urbana, IL 61801

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Chimeral `Thornless Evergreen' (CTE), (Rubus laciniatus Willd.) somaclones selected in 1983 and field planted in 1985 were reexamined in 1992 for various vegetative and reproductive characteristics. Two major types of thornless (prickle-free) plants, intermediate-sized (`UI 6-6' = `Everthornless') and dwarf (`UI 6-4'), originally selected from a chimeral thornless parent plant, were compared with thorny plants. The intermediate and dwarf somaclones have maintained their distinctive habits over 7 years' growth in the field, indicating that their growth habits are stable and not a transient effect of tissue culture. Although the thornless somaclones remained thornless, the degree and type of prickle-like structures varies considerably, indicating that the thornless gene (Ste) does not entirely suppress the production of prickles, but apparently alters their development. Increasing suppression was directly related to increasing dwarfism, suggesting a link between thornlessness and internode length.

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