ASHS 2024 Conference

Native ornamental plants, which are growing in demand in the U.S. horticulture industry, may promote biodiversity and wildlife habitat, and improve landscape resilience. To succeed in the horticulture industry, novel introductions must be aesthetically pleasing and amenable to commercial propagation and production. Bog birch (Betula pumila) is a shrub native to the United States with pubescent, ovate leaves with rounded margins that have tones of red, orange, and burgundy in autumn. In addition, young pubescent stems are brown to reddish-brown and become deep in color with a glossy finish at maturity. These qualities would make bog birch attractive within managed landscapes. We investigated the effects of auxin concentration and wounding during propagation of bog birch by softwood stem cuttings under intermittent mist. Cuttings collected in late July in northern Maine and treated with the potassium salt of indole-3-butyric acid (K-IBA) in solutions of 1,000 to 5,000 mg⋅L-1 produced greater root counts and root ratings, and longer root lengths, than cuttings treated with water alone. Cambial wounding increased root counts modestly, but was unnecessary to produce quality clones. Nearly 75% of all cuttings produced roots rated 3 or higher, the threshold at which they are transplantable. Only low concentrations of K-IBA are needed to produce root systems that meet this threshold, as transplantability increased from 55% in cuttings treated with water to 73% when 1000 mg⋅L-1 K-IBA was applied. During one season in

Pomegranate (Punica granatum) is a fruit-bearing deciduous shrub or small tree known for its nutritious and medicinal value. Its global demand is high due to rich antioxidant content, health benefits, and culinary versatility. However, the expansion of pomegranate cultivation face challenges due to the need for efficient propagation techniques that can produce high-quality plant material to meet commercial and agricultural demands. The propagation of pomegranate using cuttings is considered an easy and cost-effective method. Hardwood and softwood cuttings were treated with 3000 mg/ L indole-3-butyric acid (Hormodin® 2) and stuck in a rooting medium consisting of perlite and peat moss (4:1, v:v). Hardwood cuttings of 21 pomegranate cultivars, including ‘Al-Sirin-Nar’, ‘Angel Red’, ‘Apseronski’, ‘Arturo Ivey’, ‘Ben Ivey’, ‘Carolina Vernum’, ‘Chiva’, ‘DeAnda’, ‘Early Wonderful’, ‘Kandahar’, ‘Kazake’, ‘Kunduzski’, ‘Larry Ceballos І’, ‘ML’, ‘Mollar’, ‘Purple Heart’, ‘Russian 8’, ‘Salavatski’, ‘Spanish Sweet’, ‘Surh-Anor’ and ‘Wonderful’ were propagated in 2014, 2016, 2018, and 2023. In addition, softwood cuttings of 23 cultivars, which included ‘Al-Sirin-Nar’, ‘Ambrosia’, ‘Apseronski’, ‘Ariana’, ‘Azadi’, ‘Cranberry’, ‘Desertnyi’, ‘Eversweet’, ‘Golden Globe’, ‘Green Globe’, ‘Haku Batan’, ‘Loffani’, ‘Medovji Vahsha’, ‘Molla Nepes’, ‘Palermo’, ‘Parfianka’, ‘Phoenicia’, ‘Purple Heart’, ‘Salavatski’, ‘Sirenevyi’, ‘Surh-Anor’, ‘Vkusnyi’, and ‘Wonderful’ were propagated in 2022. The rooting percentage of hardwood cuttings was higher in ‘AL-Sirin-Nar’, ‘Salavatski’ and ‘Surh-Anor’, whereas ‘DeAnda’ and ‘Early Wonderful’ showed lower rates compared with other cultivars based on cluster analysis. For softwood cuttings, the rooting percentage did not display significant differences across cultivars, however, the number of roots were significantly higher in ‘Cranberry’, ‘Eversweet’, ‘Surh-Anor’ and ‘Wonderful’ compared with ‘Ambrosia’ and ‘Golden Globe’. Further research is needed to identify the most effective propagation technique for pomegranate production.

Plant clones, because they are the product of asexual reproduction, are populations of genetically identical individuals and are important in agriculture, horticulture, and ecology. Although clones can be maintained for hundreds to thousands of years through repeated cycles of vegetative reproduction, degeneration of plant fitness and/or productivity often occurs with increasing age and/or cycles of propagation. While powerful diagnostics allow increasingly accurate identification of the underlying causes for biotic (diseases, pest, etc., and abiotic (nutrient deficiency, inadequate chill, etc.) breakdowns in normal growth and development, genetic/epigenetic failures remain poorly understood, often being generalized as ‘off-types’. A major impediment to the effective deployment of emerging tools for identifying causes of genetic/epigenetic failures is the uncertainty as to where the failure first occurred, which is necessary to identify the most appropriate tissues for testing. Characteristic patterns of clone degeneration can be used to distinguish among different types of failure as well as recommend appropriate methods and tissues for analysis. Clone degeneration from ‘General-aging’ is due to the accumulation of many small-affect deleterious factors making targeted genetic/epigenetic diagnosis difficult though tracking changes in selected methylation profiles could serve as indicators of ‘clone-age’ particularly when ‘slow-to-age’ epicormic meristems are available for reference. ‘Bud-sports’ results from genetic/epigenetic changes in mitotically active cells resulting in distinct sectoral chimeras in subsequent shoot growth and development that can be targeted for molecular and phenotypic analysis. In contrast, ‘epigenetic-imprinting’ seems to be induced at the tissue rather than single cell level making the determination of initial induction time and site difficult to determine. In addition, because most shoot structure in temperate perennials is largely preformed during the previous growing seasons, the time and location between the initial imprinting and its first phenotypic detection can be months to years. Examples, largely from tree crop production, will be presented showing that expression patterns within these major groups can further delineate the specific nature of clone degeneration including the identification of appropriate tissues for testing.

The hot water plant (Achimenes hybrids) is a colorful gesneriad plant and can be
used as potted decorative plants indoors. These impatiens-like plants can also
be used outdoors in mixed containers and in hanging baskets. Increased
commercial production of Achimenes is limited for a couple of reasons.
Achimenes are typically propagated by rhizomes and rhizome production is
limited due to poorly understood plant responses to environmental conditions to
develop rhizomes and subsequent dormancy release. Moreover, rhizomes also
randomly develop on stolons and enlarged roots in growing media, making
harvesting challenging. One alternative method to asexually propagate
Achimenes would be from stem tip cuttings or leaf cuttings. This study
investigated three different Achimenes selections and the effects of bottom heat
and three different rooting hormone concentrations [0; 1,000; and 8,000 ppm
indole-3-butryic acid (IBA)] on root and shoot development on Achimenes leaf
petiole cuttings. Generally, leaf cuttings for all three selections developed more
shoots without bottom heat, although not always significant. All leaf cuttings, for
all selections propagated with and without bottom heat, developed roots and
shoots. The percent leaves developing adventitious shoots were lowest for
leaves treated with bottom heat for 0 and 8,000 ppm IBA in ‘A16’ at 80% and for
8,000 ppm IBA in ‘A23’ at 60%. Root ratings, based on a scale of 0 (no
adventitious roots) to 5 (significant number and length), were significantly higher
across all auxin levels for leaves grown without bottom heat in ‘A16’ and ‘A23’.
This study demonstrated that leaf petiole cuttings for Achimenes can be
successful and result in rooted cuttings producing adventitious shoots, which
could be potentially further propagated.