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Margaret From and Paul E. Read

Platanthera praeclara, commonly called western prairie fringed orchid, is a showy forb native to seven states and one Canadian province. The species had resisted previous attempts at propagation. Small, isolated populations in the sandhills region of western Nebraska are disjunct and visitation by natural pollen vectors appears to be in decline. Modern cultivation practices and other habitat encroachment factors, including urban development, recreational activities, and natural fluctuations in seasonal water availability all have the potential to exert pressure on current populations. Federal and state permits have allowed a limited hand-pollination study to be conducted on federal land. Hand-pollinated plants showed a greater fruit production compared to control plants receiving no human pollination assistance. Germination studies were conducted using aseptic in vitro techniques. The microscopic seeds possess testa that are extremely hard and resistant to liquid absorption, which presents challenges to germination in vitro. These challenges will be discussed. Alternating cold treatments with room temperatures appeared necessary to promote protocorm development after germination. Three media tested produced varying germination responses. Juvenile plants produced through micropropagation can offer propagules for possible future reintroduction efforts of this protected species.

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Handan Büyükdemirci and Paul E. Read

Axillary buds of `Valiant' grapevine (Vitis spp.) grown in vitro were transferred onto Murashige and Skoog (MS) medium supplemented with different cytokinin and auxin combinations and concentrations. It was found that culture medium caused statistically important differences in number of nodes, number of fully expanded leaves, number of multiple shoots, number of roots, and length of shoots. MS medium supplemented with 1.0 mg BA/liter in combination with 0.01 mg NAA/L was found to be the best medium for shoot growth and callus production. MS medium supplemented with the combination of 0.5 mg BA/L and 0.01 mg NAA/L was the best medium for explant rooting. The medium containing BA and NAA encouraged better shoot growth than those containing BA alone. When the concentration of BA in the medium was increased, multiple shoot proliferation and teratological structures of explants increased, but the number of small leaves and length of internode decreased. Axillary bud culture led to better shoot growth than was found for shoot apex culture. The presence of leaves positively affected shoot growth from axillary buds. Also placing the axillary buds horizontally onto the medium gave better shoot proliferation and growth than placing them vertically.

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Susan D. Schoneweis and Paul E. Read

Chimeral African violets do not come true when propagated from leaf cuttings in conventional or micropropagation systems. Chimeral plants are normally propagated by rooting suckers from mother plants. Premium prices are charged for chimeral plants due to the low numbers produced.

Reports in the African violet Society Magazine indicate that chimeral plants can be started by rooting flower peduncles. However, only one or two new plants are generated from each peduncle.

Peduncle tissue was grown in vitro to produce large numbers of plants from chimeral African violets. Ratios of plants with true-to-type vs. off-type flowers varied by cultivar and tissue used. The potential use of this technology will be discussed.

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Bahget T. Hamooh and Paul E. Read

Research was conducted to further modify the forcing solution system in order to expedite the propagation of woody plants, such as Spiraea canescens, Lonicera maakii, and Cornus alba. Time of immersion in solutions containing 5 mM silver thiosulfate (STS) was compared with the basic forcing solution reported by Yang and Read (1989), a solution containing 200 mg 8-hydroxyquinoline citrate per liter and 2% sucrose. Other treatments employed were gibberellic acid (GA3) 50 mg per liter for 24 h and a combination of STS and GA3 for the same amount of time. Increasing the time in STS solution up to 24 h led to higher percent budbreak and shorter time to budbreak for all the three species examined. The combination of STS and GA3 was the most effective treatment overall in reducing time of budbreak and increasing percent of budbreak. All STS treatments studied showed similar responses in shoot elongation. However, treatments with GA3 alone, and in combination with STS showed more than a doubling in shoot length compared to all STS treatments studied and the control. Implications based on SEM observations will be presented.

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Bahget T. Hamooh and Paul E. Read

Research was conducted in Feb. 1999 to study the effects of including silver thiosulfate (STS), gibberellic acid (GA3), or both in the forcing solution on rooting of softwood cuttings produced by forced dormant woody plant species. The cuttings were dipped for 10 s in 2000 ppm indole-3-acetic acid (IAA) or 2000 ppm indolebutyric acid (IBA). High percentages of rooting were observed in the two woody plant species examined. Root number and length of the new growth of Cornus alba and Euonymus alatus forced in a forcing solution containing the basic forcing solution treatment (8-HQC at 200 mg·L-1 + 2% sucrose), the STS treatment, or the combination treatment of STS + GA3 were not significantly different. However, treating the dormant stems of the two woody plant species examined in a forcing solution containing only GA3 led to fewer and shorter roots when compared to all other treatments. Applying either IAA or IBA to the new softwood growth led to similar root length and number for both species. This forcing solution approach provides an attractive alternative for propagating woody plants during winter months.

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Mehmet Nuri Nas and Paul E. Read

Microshoots of four hazelnut genotypes grown in vitro on Nas and Read medium (NRM) containing various combinations of CuSO4 • 5H2O and myo-inositol were successfully rooted and acclimatized ex vitro without any need of in vitro hardening treatments. Dipping of shoot bases in 1000 ppm indole-3-butyric acid (IBA) solution for 5 or 10 seconds followed by placement of shoots in plant growth regulator free NRM gave rise to formation of roots as early as 8 days. Shoots treated for 5 and 10 seconds rooted similarly, and depending on genotype, 88% to 98% rooting was observed within 15 days after treatment with IBA. Ex vitro survival of shoots three months after in vitro-root induction was 73% when shoots were treated with IBA for 5 seconds and 66% when shoots were treated for 10 seconds. The highest ex vitro survival rate (97%) 3 months after root induction was observed when shoots were treated with IBA solution for 10 seconds, and then cultured directly in peat pellets. Shoots developed good roots, and grew up to 70 cm in height 3 months after root induction. The potential use of rooting and acclimatization protocol for commercial micropropagation of hazelnut is presented.

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Hristina H. Stamenova-Berberova and Paul E. Read

Native plants are often ignored in horticulture because they may lack major ornamental traits and many of them are difficult to propagate. Creamy indigo (Baptisia bracteata Mnhl.) is a North American legume with considerable potential as a container-grown or ornamental plant for managed landscapes. Nodal explants from aseptically germinated seedlings were evaluated for axilary shoot and leaf development. The explants were cultured on Murashige and Skoog medium (MS) containing adenine sulfate at 80 mg•L-1, 30% sucrose, and different levels of N-6-benzyladenine (BA) (0.5,1.0,2.0 mg•L-1) supplemented with indole-3-acetic acid (IAA) (0.05, 0.1 or 0.5 mg•L-1) or with IAA omitted. Shoot regeneration occurred within 2 to 3 weeks. The best medium for shoot regeneration was MS supplemented with BA at 1.0 mg and IAA at 0.1 mg•L-1. Shoots were transferred onto rooting medium consisting of Ω MS supplemented with 1.0 mg alpha-naphthaleneacetic acid (NAA) and 1.0 mg indole-3-butyric acid (IBA)/L and 20% sucrose. Rooting took place within 3 to 5 weeks. Plantlets were then planted in soil mix, placed under a polyethylene tent for 2 weeks, and transferred into the greenhouse for further growth.

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Maritza I. Tapia and Paul E Read

It has been previously demonstrated that thidiazuron (TDZ) enhanced the regeneration and multiple shoot proliferation of vinifera grape cultivars. To determine the effect of TDZ on the multiplication of hybrid grapes, in vitro nodal segments from cultivars Chancellor, Leon Millot, and Valiant were cultured on MS medium supplemented with 0, 0.01, 0.05, 0.1, 0.5, and 1.0 mg TDZ/liter. After 1 month, the higher percentage of rooted shoots was obtained from the explants cultured in medium containing the lowest concentration of TDZ (0.01 mgliter–1) independent of the genotype. Multiple shoot proliferation was favored by high concentrations of TDZ (0.5 and 1.0 mgliter–1). An average of 0.39 and 0.39 shoots, respectively, was obtained from `Chancellor' cultures, 0.56 and 0.59 from `Leon Millot', and 1.93 and 2.38 from `Valiant'. Vitrification and teratological structures were observed in all the cultures of the three genotypes, but less vitrification occurred in `Valiant' plantlets.

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Paul E. Read*, William J. Waltman, and Stephen Gamet

Terroir embodies a defined place, integrating soils, geology, climate, the cultivar, and the role of cultivation, culture, and history in producing wine (Wilson, 1999; White, 2003).The understated topographic changes, thick loess soils, diffuse climatic boundaries (humid to arid), and brief viticultural history contribute to a misconception that “terroir” may not be applicable or that niche microclimates for vineyards may not exist in Nebraska. With many new cultivars and selections now available that are adapted to growing environments once considered marginal vineyard settings and the wealth of geospatial resource databases (soils, climate, and topography) available, we have begun to combine traditional field cultivar evaluation studies with the geophysical data to determine appropriate site/cultivar suitability. Our data have shown that cultivars that were previously considered unlikely to be successful may be suited to viticulture in specific locations, e.g., Riesling, Lemberger, Cynthiana/Norton, Vignoles, and Chambourcin in southeast Nebraska (our “vinifera triangle”). Mean hardiness ratings (scale 1 to 9, where 1 = dead and 9 = no injury) have been obtained for more than 50 cultivars and selections, ranging from 1.86 for Viognier to 8.66 for Frontenac and 8.71 for Saint Croix, for example. Data for most of the cultivars under test will be presented and matched with “terroirs”, providing growers with a vineyard decision support system that can help match genotypes to their specific vineyard sites and help avoid poor cultivar selection.

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Guochen Yang, Paul E. Read, and Marihelen Kamp-Glass

Chestnut (Castanea spp.) is considered difficult to micropropagate. The timing for harvesting explant materials from forced stems is critical, although many factors need to be considered for successful micropropagation. Previous research with spirea and five-leaf aralia demonstrated that forcing solution techniques extended the availability of high-quality explant material, thus expediting micropropagation. However, preliminary research illustrated that chestnut is very difficult to force and the new forced softwood growth is very short-lived, which made micropropagation difficult. It was found that, at about 7 days from budbreak, the forced chestnut softwood growth (about 2 cm long) served as the best explant material. If longer than this timing window, the new growth would die. If shorter, the explants had a high contamination rate, exudation of purported phenolic compounds, and explants would not regenerate. Shoot proliferation and callus regeneration were achieved by culturing good-quality explants on Woody Plant Medium supplemented with 0.1 mg BA/liter. The new shoots grew vigorously in vitro with apparent normal morphology.