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  • Author or Editor: Robert P. Doss x
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When compared to non-ethephon treated bulbs, time to flowering of U.S.-grown Dutch iris (Iris hollandica Hoog) ‘Ideal’ and ‘Blue Ribbon’ was shortened by 14 and 27 days, respectively, by dipping bulbs for 1 hr in a solution of ethephon at a concentration of 0.25 g·liter–1 and then heat curing at 32°C for 3 days. This treatment also decreased leaf number and maximum leaf length. Thus, the plants were commercially more acceptable than those not treated with ethephon. With ‘Blue Ribbon’, treatment with ethephon at 5.0 g·liter–1 reduced flowering percentage relative to that obtained with several lower concentrations because of prevention of flower initiation. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

Open Access

Knowledge of the chromosome number in Rubus would be valuable when planning crosses and identifying plants, etc., however, preparation of tissue for microscopic evaluation and chromosome counting is difficult and time-consuming. Flow cytometry offers a more-efficient approach to this task. DNA flow cytometry was used to determine the nuclear DNA content in 22 Rubus genotypes. The genotypes represented a range of reported chromosome numbers from 2x to 12x. Six of the genotypes were representatives of Rubus ursinus, which is reported to have both 8x and 12x forms. Samples of nuclei were prepared from leaf discs of newly emerged and mature leaves following published protocols with some modifications. The DNA content was estimated by comparison of the fluorescence of Rubus nuclei with an internal DNA standard. There was an increase in nuclear DNA content concurrent with the increase in chromosome number. In these studies DNA flow cytometry could differentiate genotypes that differed by 2x, such as 6x and 8x, but could not reliably distinguish genotypes that differed by 1x, such as 7x vs. 8x or 6x. Aneuploids cannot be differentiated at this time.

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