ASHS 2025 Conference

The session will feature presentations focused on the development and application of biotechnology in horticultural plants, followed by an open discussion on the topic and Plant Biotechnology Interest Group's business meeting.

Welcome and Opening (5 minutes)
Invited Oral Presentation (30-45 minutes)

• Speaker: Dr. Yosvanis Acanda, Simplot Company

Open Discussion (30 minutes)
Award Session (10 minutes)
Interest Group Business Meeting (30 minutes)

Cornus florida (flowering dogwood) is a valuable tree native to eastern North America and prized for its floral bracts and colorful foliage. However, the tree is highly susceptible to powdery mildew (PM), a common fungal disease that challenges ornamental plant production. There are bioengineering approaches to developing PM resistance that involve the introduction of genes into C. florida cells and the regeneration of plants through somatic embryogenesis (SE). SE is a process by which somatic cells have the capacity to produce embryos without sexual reproduction. In C. florida, the regeneration of transgenic somatic embryos into plants has been problematic. Our work aims to determine the impact of cold treatments on the germination of somatic embryos. We propose that short-term low-temperature treatments will improve embryo germination, considering past research has demonstrated the importance of periodic low temperatures on natural seed germination in woody plant species such as fruit trees. We cultured a transgenic line of C. florida embryogenic callus expressing a visual marker (ß-glucuronidase) and enriched for globular stage embryos. We then introduced these globular embryos into liquid suspension media allowing the embryos to proliferate pro-embryogenic masses (PEMs) needed for mass embryo production. We chose somatic embryos morphologically identical to zygotic embryos of the same stage of development for testing plant regeneration following exposure to four different temperature conditions over four different time periods. The four different temperatures included: (1) 3°C; (2) 4°C; (3) 7°C; and (4) 23°C as the control temperature. The four different time exposures to the different cold periods included 0, 2, 4, and 6 weeks. Following cold exposure for a designated time, we transferred the somatic embryos to germination media, exposing the embryos to fluorescent light at room temperature ( /-) 23°C. Successful germination of the somatic embryos was indicated by taproot elongation with the production of roots, greening of the cotyledons, emergence of the apical shoot, followed by expansion of epicotyl and primary leaves. This research will yield the first transgenic C. florida plants and enable the introduction of PM resistance using bioengineering methods.

Fusarium wilt, caused by Fusarium oxysporum f. sp. niveum (FON), remains a major threat to watermelon production worldwide. Effective management depends on accurate race identification, as resistance in commercial cultivars is race-specific. However, current bioassay-based race differentiation is unreliable due to genetic variability within isolates. While molecular identification exists for FON Races 1 and 2, confirming Race 3 has required multiple PCR reactions, making diagnostics cumbersome and inefficient. This study developed and optimized a multiplex PCR assay that simultaneously differentiates FON Races 1, 2, and 3 in a single reaction, significantly improving diagnostic speed and accuracy. FON isolates and related Fusarium species from Georgia, Florida, and South Carolina were tested to assess the assay’s sensitivity (0.5 ng/µL detection limit) and specificity. Results confirmed that the multiplex PCR effectively distinguishes FON from non-pathogenic Fusarium species while accurately identifying all three pathogenic races. This is the first successful multiplex PCR assay for FON race differentiation, providing a rapid, reliable tool for plant pathologists and diagnosticians to track the spread of virulent FON races. Given the increasing prevalence of Race 3, which lacks effective fungicidal control, this tool will support early intervention strategies to mitigate outbreaks and inform resistance breeding programs. Keywords: Fusarium oxysporum f. sp. niveum (FON), multiplex PCR, race differentiation, watermelon wilt.

Dormancy constitutes a critical regulatory mechanism in perennial plants, conferring resilience to winter stress and impacting subsequent reproductive success. While previous investigations have predominantly focused on vegetative and floral buds during the dormancy-regrowth cycle, often neglecting the potential contributions of other plant compartments, this study adopts a comprehensive, whole-tree perspective. Utilizing four-year-old, root-bagged peach (Prunus persica) trees (cv. 'John Boy') we investigated dormancy progression by analyzing carbohydrate metabolism in different tissues relative to accumulated chilling units (CU) and growing degree hours (GDH). Our results demonstrated that roots maintained the highest starch reserves during endodormancy; however, soluble sugar accumulation in roots appeared largely independent of local starch hydrolysis, indicating potential translocation from distal storage tissues. This hypothesis is supported by the concomitant decline in starch content in branches and stems, which coincided with increased soluble sugar accumulation in these tissues. As dormancy progressed, soluble sugars were progressively redistributed, reaching peak concentrations in roots at the onset of ecodormancy and exhibiting a more uniform distribution across tissues during ecodormancy. A significant increase in floral bud soluble sugars preceding budbreak, without a corresponding starch depletion, suggests an enhanced capacity for carbohydrate uptake. Transcriptomic analysis of root tissues across all dormancy stages identified two key gene modules (ME) exhibiting inverse correlations with carbohydrate levels. Genes within ME3, associated with starch accumulation, were significantly enriched in fatty acid metabolism pathways—including SBE2, DBE1, FAD8 and KAS1. Notably, the upregulation of FAD8 during ecodormancy suggests increased membrane fluidity, potentially facilitating carbohydrate transport. Conversely, ME10 genes, associated with soluble sugar levels, displayed enrichment in hormone signaling and carbohydrate metabolism pathways—including SUS3, BAM6, and GH9A1. These findings underscore the coordinated regulation of carbohydrate metabolism and membrane lipid composition during dormancy transitions and bud break. Furthermore, the data indicate that starch catabolism in branches and stems during chilling accumulation serves as a source of soluble sugars for roots, which in turn may sustain metabolic activity and contribute to dormancy release in buds. Future research employing this whole-tree system is warranted to elucidate the comprehensive roles of roots and other storage organs in the regulation of dormancy.

Cucumber (Cucumis sativus L.) is an economically important crop and is widely cultivated throughout the world. Cucumber plants often suffer from biotic and abiotic stresses during the whole development life cycle, which lead to reduction in yield and quality. Improvement of cucumber for disease, insect, or nematode resistance and other horticultural traits with conventional strategy is limited by long breeding cycle, narrow genetic basis, and severe incompatibility barriers in related species. Emerging plant genome editing techniques provide trait specific breeding for enhancement of plant yield, quality, stress tolerance, and disease resistance. Highly efficient regeneration and transformation system is a prerequisite for cucumber genome editing. We report an efficient Agrobacterium mediated cucumber CRISPR-Cas9 transformation system with the aid of GFP visual selection. Cotyledons from 7 days old in vitro seedlings were harvested, and inoculated with Agrobacterium tumefaciens strain GV3101 contains a binary vector with CRISPR-Cas9 gene, GFP visual selection maker and hygromycin resistance genes. Transgenic callus and shoots obtained with GFP visual selection with high efficiency. PCR double check confirmed transgenes in transgenic plants. Transgenic plants are phenotyping in the greenhouse.