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|Title:||Stability of 'Thornless Evergreen' Blackberry in Vitro and Ex Vitro (Tissue Culture, Chimera, Variability, Somaclonal Variation, Rubus)|
|Author(s):||Mcpheeters, Kenneth Dale|
|Department / Program:||Horticulture|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Plant Culture|
|Abstract:||'Thornless Evergreen', Rubus laciniatus Willd. (2n = 4x = 28), is a periclinal chimeral blackberry in which a mutated thornless epidermis surrounds a core of cells with a thorny genotype. Adventitious shoots from roots are always thorny, and gametes carry the thorny gene. Via micropropagation, pure thornless plants were selected from rapidly propagated shoot tips. These pure thornless plants had shortened internodes and a characteristic "bent petiole" condition. Isolated root segments of pure thornless plants produced thornless adventitious shoots. Micropropagated plants were placed in field plots for evaluation.
In vitro stability of chimeral explants in media with various 6-benzylaminopurine levels (0.5 to 4.0 mg/l) was evaluated. Also, various plant parts were pretreated and monitored for growth response. In addition, a series of extended-time cultures were monitored for appearance of variant types. Shortened-internode plants were produced in most treatments of these studies, but no clear trends were observed. In the extended-time experiment, shortened-internode shoots were evident after only two months in proliferation culture.
Ex vitro evaluations were made over two fruiting seasons for growth habit, vigor, flowering, and fruiting. In the third fruiting season, ploidy diagnoses were made using stomate size, pollen diameter, and chromosome number. Under field conditions, shortened-internode and chimeral plants persisted as unique types. However, somaclonal variation was evident for vigor, primocane erectness, and flowering. Thus, the shortened-internode group was subclassified into intermediate and dwarf types. No differences were observed in ploidy level or pollen diameter. Chimeral stomates were larger than intermediate-type or dwarf-type stomates; this suggested chromosomal differences or a synergistic effect due to mixed tissue types in the chimeral plants.
Weight-free selection was imposed on ex vitro field plot plants; twelve were retained for advanced testing.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-16|