ASHS 2024 Conference

Multiple Modeling Approaches Reveal Temperature Dependent Germination Traits of Vegetable Varieties - Miro Stuke
Identifying Pollinators Present on Flowers of the Pawpaw Cultivars 'Sunflower' and 'Susquehanna' - Subas Thapa Magar
Molecular Assessment of Heat Sensitivity in Broccoli Flowering - Thomas Bjorkman
Morpho-physiological Response of Plectranthus amboinicus under Flooding and Drought Stress - Samuel Asiedu
Effects of Paclobutrazol, Progressive-raising Temperature and Spike-truncated Treatments on Phalaenopsis Join Grace ‘TH288-4’ - Yi Chien Lu

In the warm growing season on the East Coast, broccoli crown development is often disrupted because insufficient cold accumulation for flower bud initiation and enlargement. As part of an effort to breed for adaptation to higher growing temperatures, we investigated whether the sensitivity is due to expression of one or more of the central genes involved in flower initiation. Broccoli transitions from vegetative to reproductive phase normally, it is the transition from reproductive meristem to floral meristem and flower bud that is arrested or delayed in warm temperatures. We compared the heat response of a highly sensitive genotype, ‘Clara’ and the most resistant available genotype ‘P13xP19’ (P. Griffiths, Cornell). Plants that had just entered the reproductive phase were exposed to temperatures that were either permissive (16/12°C Day/Night) or restrictive (28/22°C Day/Night) for three days, then RNA was isolated from the meristem. The RNA was sequenced, transcripts were identified and relative abundance of each transcript was determined. Transcripts were available corresponding to the genes of interest. The model is that various developmental and environmental cues affect expression of the integrator gene SOC. The expression level of SOC then influences a gene that maintains meristem (TFL1) and one that promotes flower development (LFY). The interplay between those genes in time and space is believed to control how big the meristem will get and when the meristem will start to make flowers. When LFY expression dominates, it promotes expression of AP1 (and paralogs) inducing floral primordia. A gene responsible for the heat sensitivity would have differential expression in heat only in the sensitive genotype. That was the case for TFL1 and one copy of SOC1, but not for the other genes. Therefore, heat sensitivity is caused by genes associated with meristem transition, not with the classic flower-initiation genes.

Do Plant “Growth Regulators” Really Regulate Growth? Plant Development And Plant Growth Are Not Synonymous. - Ted DeJong
Using GDR to Enable Rosaceae Research - New Data, Functionality and Future Direction - Dorrie Main
Raspberry Cultivar Evaluation Trial in Mississippi - Apphia Santy
Evaluating Sufficiency Levels and Peach Leaf Analysis for Fertilizer Decision-Making - Juan Carlos Melgar
Common Mechanisms Controlling Fruit Shapes may be Mediated by Changes in Cell Wall Properties - Easther van der Knaap
Pomological Nomenclature: Recent Developments and Problems - David Karp

Much scientific literature refers to plant development and growth as though they are synonymous. While plant physiology texts (E.g., Taiz et al. 2015) and horticulture texts (E.g., Sansavini et al. 2019) emphasize the roles of various plant hormones in coordinating plant development, they simultaneously refer to them as plant growth regulators. On the other hand, the same texts emphasize assimilation processes and the important role of carbohydrate and nutrient availability as well as water relations in enabling growth to occur. The terms growth and development are often used interchangeably and the literature rarely emphasizes the difference between plant development and plant growth. This causes confusion and a lack of clear thinking when attempting to develop explanations for plant growth responses in specific circumstances. Hormone physiologists often try to explain particular growth responses in terms of hormonal theory whereas environmental physiologists will likely explain the same responses in terms of environmental conditions and availability for the resources required for achieving growth. In this paper I will argue for a clearer differentiation between plant development and plant growth and suggest that plant hormones should not be thought of as plant growth regulators, but rather as plant development coordinators. Plant development coordinators (plant hormones) set up the conditions necessary for plant growth but availability of plant growth substances; carbohydrate and nutrient availability along with temperature and water relations, are often what actually regulate plant growth rates. Treating development and growth as separate but interdependent processes could clarify much understanding of the underlying processes involved in the regulation of plant growth. These concepts will be discussed in the context of understanding the mechanisms involved in several physiological phenomenon of fruit trees.

Initiated in 2003, the Genome Database for Rosaceae (GDR, www.rosaceae.org) is a comprehensive community database that provides access to curated and integrated genomics, genetics, and breeding data for the biologically and economically important Rosaceae family. It serves as steward of critical research and breeding data, and provides access to online query and analysis tools that enable researchers to readily interrogate this wealth of data, facilitating basic and applied research across Rosaceae. This presentation will highlight the impact of GDR on Rosaceae research, demonstrate new data and tools, and share plans for future development and sustainability options.

Many states in the US produce raspberries, however, most of the production is concentrated in three states: California, Oregon and Washington as most raspberry cultivars grow best in regions with cool summers and mild winters. However, newer raspberry cultivars have been developed exhibiting heat tolerance. Cultivars with heat tolerance provide an opportunity for the growers in the Southern states to include raspberries in their crop production. Local Mississippi growers are interested in incorporating raspberries into their productions. However, there lacks research-based recommendations on raspberry cultivars suitable for Mississippi's climate. The objective of this study was to evaluate raspberry cultivars in terms of plant growth, heat and cold tolerance, pest and disease resistance, berry yield, quality, and fruiting season to identify the best-suited cultivars for Mississippi. This experiment was conducted in a randomized complete block design with two types of fertilizer: conventional and organic. Data collection included measurements of plant growth and performance, berry yield and quality and fruiting season. The results showed that raspberry yield, single berry weight and fruit size were influenced by fertilizer treatment. The soluble solid contents, acidity, and fruit color were not influenced by fertilizer treatment. Raspberry yield was higher for “Polka”, “Encore”, “Heritage”, and “Latham” under conventional fertilizer. Cultivars “Himbo”, “Prelude”, ‘Bp1”, and “Encore” treated with conventional fertilizer had higher single berry weight. The average fruit size of cultivars “Prelude”, “Himbo”, “Encore”, “Bp1” treated with conventional fertilizer produced larger fruits in comparison to the other cultivars. The fruit's soluble solid content was highest in “Heritage”, indicating a sweeter taste. Cultivars “Polana” and “Anne” produced fruits with the highest acidity, indicating a tarter taste compared to other cultivars. Fruit color varied between cultivars, with differences in lightness, redness, and yellow coloration.

The increasing demand for tree fruit production necessitates optimizing nutrient balance in intensified orchard systems to maximize profits efficiently. While peach growers are advised to follow Extension and recommended guidelines for fertilization, such recommendations may not align with orchard-specific variables and environmental conditions. As a consequence, crop sufficiency ranges may require updating to reflect modern growing practices and environmental factors. Although leaf nutrient analysis is the most reliable method for diagnosing tree nutritional status, the prevalence of annual fertilizer application, driven by the low cost of fertilizers relative to crop value, often leads to excessive fertilization in peach orchards. Consequently, our objective was to evaluate established sufficiency levels and leaf analysis as tools for determining the need for annual fertilizer applications. To achieve this, we implemented a two-year study involving two fertilization programs in an orchard with three rows of 17 peach trees: two rows adhered to grower standard, annual fertilization, while the remaining row followed a rational fertilization program. The latter implied applying fertilizer only when leaf analyses indicated nutrient concentrations below established sufficiency thresholds for peaches. Leaf analyses were conducted annually in July, and if nutrient concentrations were within or exceeded sufficiency thresholds, no fertilizer was applied postharvest or the following spring. If nutrient concentrations fell below sufficiency thresholds associated with a significant difference in yield and fruit quality between the two programs, fertilization occurred in late summer and during bloom time the following spring. We assessed tree quality and productivity by measuring yield (total weight of all the fruit per tree) and fruit quality (size and brix) annually. The results of the first year showed that despite deficient leaf nitrogen and phosphorus concentrations and other nutrients such as potassium, calcium, and magnesium remaining within or above their sufficiency ranges, we observed no significant differences in yield or fruit quality between trees subjected to rational and standard fertilization practices. Consequently, fertilization for the upcoming year was deemed unnecessary in trees following the rational program. The outcomes of this study are expected to guide peach growers in making informed decisions based on updated data, reducing the environmental impact of overfertilization, which is inefficient for fruit production and uneconomical, and enhancing farm profitability.

Fruit shape variation is abundantly present in horticultural crops. This variation is critical to highlight the market class as well as the culinary purpose of the produce. Many of the underlying genes have been cloned in tomato, offering insights into the molecular mechanisms of morphological diversity. Specifically, members of the OFP, TRM and SUN family regulate produce shape variation in tomato and other crops, thereby highlighting the importance of these three families in regulating phenotypic diversity. Despite the knowledge of the genes, mechanistic insights into the function of members of these three gene families are lacking. Our research on the tomato genes OVATE and OFP20 has shown that changes in produce shapes are noticeable early in the development of the flower. Cell counts in ovaries at anthesis implied that changes in cell division patterning may underlie morphological diversity. However, gene expression studies showed that morphological changes were associated with cell wall processes and not with changes in cell division patterning.

In addition to botanical names, at least a dozen distinct categories of nomenclature are applied to plant cultivars, including various forms of cultivar denominations, breeders references, and trade names. Two sets of rules, the International Code of Nomenclature for Cultivated Plants (9th ed., 2016), and the Explanatory Notes on Variety Denominations Under the UPOV Convention (2022) provide current guidelines for plant cultivar nomenclature. In some instances UPOV and ICNCP rules differ, and stakeholders may wish to consider whether it would be feasible to seek harmonization, and the mechanisms by which that might be achieved. This session will trace a brief history of cultivar denomination rules for U.S. plant patents. The United States Patent and Trademark Office, which issues plant patents, does not provide detailed nomenclatural guidelines. In the past two decades a new model for plant nomenclature has prevailed, in which an alphanumeric code serves as the official cultivar denomination, and this is paired with a trademark, either registered or unregistered. The relationship between cultivar denominations and trade names can be complex and fluid. As co-editor of the Register of New Fruit and Nut Cultivars, the presenter professionally researches all new pomological cultivar denominations and trade names, to avoid publishing names that conflict with previous names or nomenclatural standards. The establishment of an official cultivar denomination has important practical consequences that are sometimes ignored by breeders and rights owners. When a cultivar has been granted a plant patent or plant breeders’ rights, the cultivar denomination recorded by the statutory plant registration authority that issues the grant becomes officially established (a “statutory epithet”), and cannot be casually changed or replaced by the rights owner. When such informal synonyms are used, they are best regarded as trade names, often as unregistered trademarks. Common mistakes and pitfalls in nomenclature are described.