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 Title: Regeneration and germination of cucumber seeds in vitro and a study of delayed flowering gene (df) Author(s): Ali, Nawab Doctoral Committee Chair(s): Skirvin, Robert M.; Splittstoesser, Walter E. Department / Program: Crop Sciences Discipline: Crop Sciences Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Biology, Genetics Agriculture, Plant Culture Abstract: Old and fresh seeds of various cucumber (Cucumis sativus L.) lines were studied for germination and cotyledon regeneration. Depending on cultivars, seeds stored at 68$\sp\circ$F and 38% relative humidity remained 40 to 90% viable for 13 years. Seeds older than that were nonviable. It was also found that removing 1/4 cotyledon from fresh cucumber seed increased root number, length and hypocotyl growth. To develop an efficient cotyledon regeneration system, shoot regeneration from 1/6, 1/4, 1/2, 3/4 cotyledon segments was compared with shoot regeneration frequency of full cotyledon. It was found that shoot regeneration efficiency of full and 3/4 segments was statistically low compared with the rest of the treatments. No statistical differences were found in regenerability of 1/6, 1/4, and 1/2 segments of cucumber cotyledon. It was also found that position of segment relative to embryonic axis has no effect on shoot regeneration. It could be that endogenous growth regulators are evenly distributed in cucumber cotyledon. MS medium with kinetin (3 mg/L) enhanced the later growth of regenerated shoots.Gene df, found in 'Baroda' cucumber, has been associated with delayed flowering and delayed germination. The effect of this gene was studied in two cucumber lines ('Baroda' and 'Marketer'). It was found that the gene df alone is not responsible for inducing dormancy. The reported dormancy could be due to the interaction of df with modifiers or some other genetic or cytoplasmic factors. It was found that the mechanism of dormancy lies in the seed testa. This seed coat layer either restricts water uptake or, most likely, is impermeable to gas exchange. Dormancy, however, can be broken by puncturing this thin layer. Issue Date: 1990 Type: Text Language: English URI: http://hdl.handle.net/2142/20076 Rights Information: Copyright 1990 Ali, Nawab Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9026119 OCLC Identifier: (UMI)AAI9026119
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