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- Author or Editor: Peter D. Ascher x
Abstract
Callus initiated from bulb-scale expiants of the interspecific hybrid Lilium ‘Black Beauty’ on a Linsmaier-Skoog (LS) semisolid medium containing 4 mg/liter 2,4-dichloro-phenoxyacetic acid (2,4-D) was transferred to liquid LS with or without 4 mg/liter 2,4-D and incubated in darkness on a gyrorotary shaker at 100 rpm. Every 7 to 10 days the callus was transferred to fresh medium. The culture was maintained for 3 years. Plants were generated from the callus on semisolid LS at 1 year and 30 months after initiation of the liquid culture. Differentiation began with root formation, then shoots were produced. Supplementing the semisolid medium with 0.3 mg/liter α-naphthaleneacetic acid (NAA) stimulated root formation but shoot production was best on medium without growth regulators or medium containing 0.03 mg/liter NAA. Eleven of the 58 plants recovered (19%) bore variegated foliage but none of the 40 which flowered, including 2 with variegated leaves, deviated from the floral phenotype of ‘Black Beauty’.
The change from asexual to sexual propagation for annual and perennial bedding plants has been successfully accomplished for floral crops, e.g., Pelargonium. Seed-propagated cultivars do not necessarily possess the clonal uniformity of vegetatively propagated cultivars. In the development of F1 hybrid garden chrysanthemums, this lack of uniformity was assessed with the use of consumer sensory evaluations. Seedlings (n = 10–20 plants/cross) were transplanted for field trials in St. Paul and five Minnesota branch stations each year during 1988–94 to test for G × E. Early flowering F1 hybrids, developed from inbred parents with general combining ability, were evaluated for flowering earliness, plant uniformity, and a general rating. Consumer rankings of top performers were not significantly different (5% level) from mum breeders. The top performers for all three ratings were selected each year for repeat evaluation the next year. The two highest performing F1 hybrids were submitted for All American Selection Trials in 1995.
Abstract
About 2000 pollinations of Pbaseolus coccineus × P. acutifolius, P. coccineus × P. vulgaris, P. vulgaris × P. acutifolius, and F2 (P. vulgaris × P. coccineus) × P. acutifolius produced more than 1500 excisable embryos, about half of which elongated and produced leaves and roots when embryo cultured on a relatively simple medium in the dark. Damaging cotyledonary buds on small embryos or removing cotyledons from larger embryos before culture enhanced germination. Transplanting germinated embryos into pots resulted in greater than 50% mortality. Hybrids tended to be intermediate to parental species in vegetative and floral characteristics but percent stainable pollen was lower. Anthers did not dehisce and percent stainable pollen was lowest in P. vulgaris × P. acutifolius and F2 (P. vulgaris × P. coccineus) × P. acutifolius hybrids. Since P. coccineus × P. acutifolius and P, coccineus × P. vulgaris hybrids were sufficiently fertile to produce advanced generations, P. coccineus may be useful as a bridge between P. vulgaris and P. acutifolius.
Abstract
Equal half-root systems of cowpea seedlings were achieved with a split-root technique. By use of a high humidity chamber and growth pouches, it was determined that the survival rate of seedlings with bisected root systems was greater than 95%, and the development of the half root systems was uniform and adequate. There were no marked differences in growth and development of plants when treatments were applied to different halves of the root system. However, there was evidence of Zn translocation from noninoculated half-root systems which received Zn, to inoculated half-roots not receiving Zn, which resulted in increased nodulation and N2 fixation. This result supports reports of a direct relationship of Zn nutrition to nodulation and N2 fixation.
Abstract
A nondestructive measurement technique for predicting the developmental stage of young embryos was devised and used to study developmental patterns of 2 Phaseolus crosses. While selfed P. coccineus Lam. produces normal seeds, P. coccineus × P. vulgaris L. aborts embryos when the seeds reach 10 mm in length. Seed growth of the interspecific cross was reduced with respect to days after pollination. Other characteristics of the interspecific cross included reduced pod length, an increased (pod length)/(number seeds per pod) ratio, reduced embryo fresh weight, and an increased volume of liquid endosperm. Between the self and the cross, pod thickness did not differ, and thus can be used to predict developmental stage of young embryos.
Pollination of the half-high blueberry (Vaccinium corymbosum L./V. anugustifolium Ait.) cultivars St. Cloud, Northsky, Northcountry, and Northblue with self, outcross, and outcross/self pollen mixtures suggests that outcross fertilization maximizes percent fruit set, berry weight, seeds per berry, and seeds per pollination while minimizing days to harvest. Based on these results, mixed plantings of at least two blueberry cultivars are recommended for these cultivars. Fruit and seed set were negatively associated with increased percentages of self pollen in outcross/self pollen mixtures. These responses were linear for `Northblue' due to a tendency to parthenocarpy, and nonlinear for `St. Cloud', `Northsky', and `Northcountry', due to low fruit set following self-pollination. These data indicate that post-fertilization abortion affected seed formation, which was, in turn, correlated positively with fruit set.
Abstract
Leaf emergence from bulblets of Lilium longiflorum Thunb. generated in vitro from bulb-scale explants incubated in the dark at either 25 or 30°C was enhanced by 3 stimuli: incubation at 4°C for 1 or more weeks after removal from culture; immersion in water at 45° for 30 minutes to 8 hours after removal from culture; or in vitro red-light irradiation. For maximum response, bulblets generated at 25° required longer treatments at either 45° or under red-light irradiation. On the other hand, bulblets generated in vitro at 30° responded least to incubation at 4°. Although all 3 environmental factors ended dormancy, variation in rates of leaf emergence and total percentage of bulblets with leaves at the end of the experiments suggested differences in the state of bulblet dormancy due to in vitro temperature and differences in the physiological action of the environmental stimuli promoting leaf emergence.
Abstract
Up to 50% of bulblets generated in vitro at 30°C from bulbscale explants of Lilium longiflorum ‘Ace’ produced an elongated axis in the 14 weeks after removal from tissue culture and potting in vermiculite. None of the ‘Ace’ bulblets produced in vitro at 25° and none of the ‘Nellie White’ bulblets produced in vitro at either 25° or 30° formed an elongated axis. Increased length of time that ‘Ace’ bulbs were stored at 4° before explanting as well as immersing bulblets generated in vitro at 30° in water at 45° for 1 hour before potting increased the percentage of bulblets with an elongated axis. Axis elongation was not related to bulblet size or to position of scale used for explanting (inner vs. outer bulb scale). Exposing ‘Ace’ bulblets generated at 30° to 3 or more weeks at 4° reduced the percentage of bulblets with an elongated axis to zero. Treatment of chilled bulblets for 2 hours in water at 45° did not reverse the effect of cold.
Abstract
Seeds of 29 terrestrial orchid species representing 15 genera were surface sterilized by immersion in 0.5% sodium hypochlorite containing a wetting agent, washed, sown on a completely defined, semisolid embryo culture medium containing macro- and microelements, sucrose, amino acids, and vitamins, and incubated in the dark at 25°C. Six months after sowing, 16 species from 9 genera germinated and continued development while 13 species from 10 genera failed to germinate. Species of Cypripedium, Goodyera, Platanthera and Spiranthes differed in response in that one or more of each germinated and one or more did not. Seedling development was similar for most germinating species and progressed to the formation of a shoot or shoot initial in all but one. Apparently the mycorrhizal association thought to be required for terrestrial orchid seed germination and early seedling development can be replaced with aseptic culture on a completely defined medium for many terrestrial orchids.
Our objective was to determine whether repeated applications of 2-chloroethylphosphonic acid (ethephon) + gibberellic acid (GA3) to stock chrysanthemum plants that are day-neutral for flower bud initiation would increase the number of quality cuttings. Across five cultivars, there were no significant differences between controls and plants receiving 250 ppm ethephon in the total number of cuttings per plant. The percentage of cuttings with crown buds was greater for cuttings from controls than for ethephon-treated plants. Applying 500 ppm ethephon significantly reduced the number of cuttings. We conclude that chrysanthemum clones day-neutral for flower bud initiation and development with low long-day leaf number could be selected to form a 4 to 5 week production group.