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  • Author or Editor: Jessica D. Lubell-Brand x
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Epimedium is a genus of shade tolerant herbaceous perennials and groundcovers that are slow growing and command high prices. This research examined the influence of division size and timing on propagation success and growth of E. pinnatum ssp. colchicum Boiss., E. × rubrum Morren, E. × versicolor `Sulphureum' Morren and E. × youngianum Fisch. To determine an appropriate division size for each species, small (single bud) and large (three bud) divisions were made in mid-June 2002 and 2003. For the timing study, uniform divisions (three to five buds for E. pinnatum ssp. colchicum and E. × versicolor `Sulphureum'; four to seven buds for E. ×rubrum and E. × youngianum) were made in March, late June and late August, when plants were dormant, had just completed foliage expansion, or were summer dormant. Half of the plants were destructively harvested in the fall and half were overwintered and forced in the greenhouse in early spring. By the end of the growing season, plants grown from large divisions were larger than those grown from small divisions and had produced more buds, however, plants from small divisions produced more buds per initial bud than plants from large divisions, demonstrating a faster increase in growing points. For each species, March divisions produced more vegetative growth, buds, buds per initial bud and potential propagules than June and August divisions, by the end of the growing season. However, by the following spring, both March and June divisions had produced plants of similar size and appearance, while plants grown from August divisions were smaller and of lower quality.

Free access

Interest in hemp (Cannabis sativa) for its medicinal compounds, cannabidiol (CBD), and Δ-9-tetrahydrocannabidiol (THC), continues to increase. Maximizing yield of CBD and/or THC requires female plants because female inflorescences accumulate significantly greater concentrations of these compounds than male inflorescences. Production of all female seed requires induction of female plants to develop male flowers that produce genetically female pollen. Growers would like access to feminized seed to produce all-female crops. We evaluated the efficacy of 0, 0.3, and 3 mm silver thiosulfate (STS) applied as a foliar spray (on three occasions 7 days apart) to produce male flowers on four strains of female hemp (having a THC concentration of ≤0.3%), designated CBD hemp A, CBD hemp B, CBD hemp C, and industrial hemp. Silver thiosulfate at 3 mm was the most efficacious treatment for all strains. The majority of inflorescences had 100% male flowers at 3 mm STS, and terminal inflorescences had ≥95% conversion to male flowers. Silver thiosulfate at 0.3 mm produced partial conversion to male flowers, whereas most inflorescences had around 50% male flowers, except for CBD hemp A, which demonstrated greater levels of masculinization. At 0.3 mm STS, terminal inflorescences of CBD hemp A had 91% conversion to male flowers. This study demonstrates that male flowers can be produced easily and consistently on female plants through application of foliar sprays of STS under short-day conditions.

Free access

Red-flowered elepidote rhododendrons (Rhododendron sp.) are favored by consumers, but cold-hardy red-flowered rhododendrons frequently have blue-red flower hue rather than the preferred red flower hue. Flower longevity, color, and color stability over 14 days were studied for the following eight elepidote rhododendron cultivars possessing red flowers: Besse Howells, Burma, Cary’s Red, Firestorm, Francesca, Henry’s Red, Low Red Frilled, and Nova Zembla. The eight cultivars were separated by flower hue into two distinct groups of four cultivars each. Rhododendron cultivars Burma, Firestorm, Francesca, and Henry’s Red produced flowers with red hue and Besse Howells, Cary’s Red, Low Red Frilled, and Nova Zembla produced flowers with blue-red hue. Flower longevity among rhododendron cultivars varied with Francesca blooms lasting the longest at over 14 days, and Besse Howells and Firestorm blooms lasting the shortest at 10 days. As flowers aged, hue angle decreased (became bluer), lightness increased, and chroma decreased or remained unchanged. The degree of change in flower color over time differed among cultivars, with ‘Francesca’ demonstrating the least change (ΔE 00 3) and ‘Besse Howells’ the most change (ΔE 00 11).

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Genetically female seed is sought for cannabidiol (CBD) hemp production because CBD is extracted from the flowers of female hemp plants. The production of all female seed requires masculinization of female plants to produce genetically female pollen that reliably generates female seed. Of the five female hemp genotypes that we masculinized using foliar sprays of silver thiosulfate (Abacus, Cherry Wine, Mountain Mango, Youngsim10, Wife), all genotypes produced fewer large and more irregular or misshapen pollen grains than genetically male plants. The masculinized female genotypes Wife and Cherry Wine produced pollen with germination rates similar to those of the male genotype Kentucky Sunshine. Female hemp genotypes vary in their ability to produce usable pollen that disperses well, is easily collected, and germinates as well as pollen from genetically male hemp plants.

Open Access

Northern bayberry [Morella (formerly Myrica) pensylvanica] is an attractive, adaptable, semievergreen, northeastern North American native shrub that is sought for landscaping but difficult to propagate clonally. The impact of timing (June, July, or August) and concentration of indole-3-butyric acid [IBA (0, 2000, 4000 or 8000 ppm)] on propagation by stem cuttings was evaluated for genotypes of northern bayberry including the female cultivars Bobzam (Bobbee™) and UConn Compact and an unnamed male. Medium formulation and cytokinin type were evaluated for micropropagation of ‘Bobzam’ and ‘UConn Compact’. Stem cuttings of ‘Bobzam’ and ‘UConn Compact’ rooted poorly (at ≤55% and ≤20%, respectively) at all timings and concentrations of IBA; however, rooting success of ≥85% was achieved for the unnamed male genotype when cuttings were taken in June. Micropropagation of ‘Bobzam’ was successful using Woody Plant medium with 4 mg·L−1 zeatin and explants taken from shoots that had expanded 12 to 18 cm on containerized stock plants. Initiated explants of ‘Bobzam’ required eight subcultures before they began to produce shoots consistently at a 2× multiplication rate and eventually reached a 3× multiplication rate. Micropropagation attempts using Murashige and Skoog medium, the cytokinins 6-benzylaminopurine, meta-topolin, and thidiazuron, or the cultivar ‘UConn Compact’ were unsuccessful. Microshoots of ‘Bobzam’ rooted at ≥80% either by in vitro prerooting or ex vitro rooting directly in trays. Rooted microcuttings easily acclimated to greenhouse conditions and grew rapidly when potted to 1.04-L containers and then into 5.68-L containers. The micropropagation protocol developed for ‘Bobzam’ can be used by propagators to expand production of this popular female cultivar.

Open Access

There is demand for early-flowering cannabis (Cannabis sativa) cultivars to hasten harvest and avoid late-season detrimental weather conditions. A field study and greenhouse studies were conducted to evaluate the effect of gene dosage at the autoflowering locus on flowering timing for diploid and triploid hybrids between autoflowering and photoperiod-sensitive parents. Autoflowering × photoperiod-sensitive hybrids were all photoperiod sensitive, but their critical photoperiods were longer than for homozygous photoperiod-sensitive plants, which resulted in earlier flowering. For triploid genotypes, decreasing dosage of the photoperiod-sensitive allele (A), from AAA to AAa to Aaa, reduced the time to flowering. Flowering timing for the diploid genotype Aa was intermediate between Aaa and AAa. These results provide evidence of incomplete dominance of the A allele at the autoflowering locus. Plants of genotype Aaa flowered 32 to 40 days earlier in the field than genotypes of AA, 15 days earlier than genotype Aa, and were ready for harvest by the second week of August in Connecticut. Plants of Aaa were as tall as other diploid and triploid photoperiod-sensitive genotypes studied, which suggests that they have similar yield potential. The use of tetraploid autoflowering (aaaa) maternal plants in combination with diploid photoperiod-sensitive (AA) pollen parents to produce Aaa genotype seed is a reliable approach for developing early-flowering cultivars of cannabis for flower production purposes.

Open Access

Aroniaberry (Aronia mitschurinii) produces small pome fruits that possess health promoting compounds. Management practices for orchards are lacking, since aroniaberry is a relatively new crop. Pruning is an important cultural practice to optimize fruit yield in orchards. The response of an established aroniaberry orchard to pruning was evaluated over three years (2020 to 2022). Pruning treatments were as follows: 1) renewal pruning (removal of shoots to the base) only in year 1; 2) renewal pruning in year 1 + thinning to 18 shoots in year 2; 3) renewal pruning in year 1 + thinning to 9 shoots in year 2; and 4) no-pruning (control). In response to renewal pruning, plants grew uniformly and vigorously, producing 28 new vegetative primary shoots with an average length of 66 cm by the end of the first growing season. Limited flowering and fruiting occurred in the second season for plants receiving pruning treatments. Fruit yield on pruned plants was significantly less than for unpruned controls. In season 2, increased thinning of renewal-pruned plants negatively affected the number of inflorescences per plant, but positively affected individual fruit fresh weight and fruit °Brix:titratable acidity ratios. Fruits from all treatments had similar monomeric anthocyanins, total phenolics and mineral content. In season 3, flower production and predicted fruit yield from pruned plants and unpruned controls were similar, even though pruned plants were substantially smaller. In the third season, there were no longer any differences between renewed + thinned plants and those that received only renewal pruning, making shoot thinning an unnecessary practice. The results of this study demonstrate that renewal pruning can be an effective way to manage and rejuvenate an aging aroniaberry orchard.

Open Access

To maximize yield, cannabidiol (CBD) hemp producers prefer female plants, and this is accomplished by using expensive feminized seed, vegetatively propagated female clones, or by removing male plants from dioecious seed lots. Hemp pollen drifts long distances on wind, and pollination of females reduces CBD content. Induction of triploidy is a common strategy used by plant breeders to produce sterile cultivars of agricultural crops. Triploid (3n) hemp, with three sets of chromosomes, was developed by crossing naturally diploid (2n) hemp with tetraploid (4n) hemp. Tetraploid plants used to create triploids were produced using pregerminated seeds and the mitotic spindle inhibitor colchicine. Seedlings from seeds of ‘Abacas’ × [(‘Otto2’ × ‘BaOx’) × (‘BaOx’ × ‘Colorado Cherry’)] treated with 0.05% colchicine or 0.02% colchicine for 12 hours and longer were significantly shorter than controls and ≤1 cm tall at 10 days after sowing. Surviving seedlings exhibited thickened cotyledons and hypocotyls, which indicated a potential change in ploidy. Tetraploid induction ranged from 26% to 64% for pregerminated seeds of five different hemp cultivars (Abacus × Wife, Cherry Wine, Mountain Mango, Wife, and Youngsim10) treated with 0.05% colchicine for 12 hours. Tetraploids had nearly twice the DNA content as diploids according to flow cytometric analysis. Tetraploid ‘Wife’ had larger stomates and reduced stomatal density compared with diploid ‘Wife’. Four triploid ‘Wife’ genotypes produced from crossing tetraploid ‘Wife’ with diploid ‘Wife’ were acclimated to greenhouse conditions after embryo rescue. DNA content and stomate size of triploid ‘Wife’ was intermediate between the parents. This is the first report of triploid plants of hemp. Future research will evaluate the sterility of triploid hemp.

Open Access