ASHS 2025 Conference

This talk presents an integrated approach combining metabolomics and proteomics to advance plant research. By connecting metabolic profiles with protein expression and function, we can gain deeper insights into plant function, stress responses, and development, with implications for crop improvement and sustainability. The presentation will highlight recent methodological advances, case studies, and the potential of multi-omics approaches to drive innovation in plant science research.

As a member of Convolvulaceae family, sweetpotato (Ipomoea batatas L.) is an important crop for food security. As one of the top three vegetable crops grown in Mississippi, one major limitation to sweetpotato production is the cumulative effect of virus infection leading to cultivar decline and yield losses. To produce virus-tested sweetpotato seedlings, we developed meristem-tip culture technology combined with heat treatment to provide farmers with healthy propagating materials that are free of detectable viruses. In this study, totally 30 lines of sweetpotato have been collected in Mississippi and beyond. The plants were first examined with the infection of five of the most prevalent viruses by using nucleic acid-based polymerase chain reaction (PCR) and reverse-transcription PCR (RT-PCR) techniques, which showed high sensitivity and confirmation at the genomic level of viral species and strains. Primers targeting to conserved regions of the know sweetpotato viruses were used for this nucleic acid based detection. The effective protocols for sweetpotato viral detection and viral removal were well developed in this study. The optimized protocols have been used for the purpose of viral detection and eradicating from elite sweetpotato lines in Mississippi. Virus-free planting material has been propagated in Agriculture Research Station of Alcorn State University for performance evaluation.

Bigleaf hydrangea, Hydrangea macrophylla, is a popular ornamental shrub beloved worldwide for its large colorful inflorescences. As of 2019, bigleaf hydrangea topped $155 million in total sales in the United States. However, diseases impact the health, appearance and ultimately the salability of bigleaf hydrangea. One such disease is powdery mildew, caused by the fungus Golovinomyces orontii. Powdery mildew is a biotrophic obligate, which means that it will only grow on a living host, making it particularly hard to investigate. Inoculating plants via tapping infected leaves against clean leaves is the most common inoculation method; however, this method results in an unknown amount of inoculum and inconsistent infection. Quantifiable and consistent methods are needed to accurately and reproducibly study powdery mildew disease of bigleaf hydrangea. The purpose of this experiment was to compare two inoculation methods, an inoculation box and spray inoculation method, for inducing powdery mildew disease in bigleaf hydrangea. For the box inoculation, 6 infected leaves per plant were tapped above a 48-micron mesh and gently dusted through to land on the plant surface. A still air chamber was designed to be set over the box so that powdery mildew does not get disturbed by air currents. For the spray inoculation, 6 infected leaves per plant were combined into a spray by rinsing the leaves with deionized water, adding Tween 20 to aid with even dispersion and applied to the plant using a spray bottle. Powdery mildew was then evaluated on a scale of 0-100% and the area under disease progress curve (AUDPC) was calculated. The final disease severity of hydrangea inoculated via the box and spray method after 4 weeks of observation were 10.0 and 20.0%, respectively. These results will provide valuable information on more consistent inoculation methods using powdery mildew.

Blueberry (Vaccinium spp.) is one of the most economically important woody plant species because its fruit is rich in antioxidants such as anthocyanin, which offer beneficial effects on human health. Thus, the demand for blueberry production and for the development of novel elite cultivars has been continuously increasing. Although new blueberry cultivars have been developed by cross breeding for more than a century, the conventional breeding approaches are time-consuming and labor-intensive due to the associated characteristics that hinder efficient breeding such as long juvenile phase, polyploidy, and heterozygosity. Genetic engineering offers a promising approach to confer a desirable trait to elite cultivars. In particular, the recently developed genome editing technology enables precise modifications of plant genomes. We aim to apply genome editing to improve agronomically important traits in blueberry, specifically anthocyanin and sugar content. Towards the development of high anthocyanin blueberry, we targeted an anthocyanin repressor gene, VcMYBC2. So far, we successfully obtained 3 lines with all-alleles of VcMYBC2 were mutated. An increase in anthocyanin content in fruit is expected in the mybc2 mutants. Regarding sugar content, we targeted invertase inhibitor (INVINH) gene that is involved in sugar metabolism. Invertase promotes sucrose unloading in the fruit by maintaining a gradient of sucrose concentration between source leaves and fruits, while INVINH represses this process. Thus, higher sugar accumulation is expected in invinh mutants. Three transgenic lines harboring CRISPR-Cas9 vectors targeting VcINVINH genes that are highly expressed in fruit tissue, were obtained. The mutated allele frequencies of the mutants ranged from 21-67%. Additionally, we generated transgenic blueberries overexpressing FLOWERING LOCUS T (FT), a mobile florigen signal gene that induces flowering. A previous study demonstrated that blueberry scions grafted to FT-overexpressing lines could show early flowering. We thus assume that the mybc2 and invinh mutants may flower earlier when they are grafted onto the FT overexpressing rootstock, which will accelerate our fruit phenotype evaluations. The FT-overexpressing rootstock may also be utilized to facilitate the production of null-segregant mutants.

Agrobacterium-mediated transformation is widely used in plant genetic engineering. This method involves both Agrobacterium infection and plant regeneration. In this context, establishing an efficient plant regeneration system is a critical prerequisite for genetic engineering in plants. This study aims to identify highbush blueberry (Vaccinium corymbosum L.) cultivars suitable for genetic transformation. Furthermore, we seek to elucidate the molecular and genetic factors that determine genotype-dependent shoot regeneration capacity by utilizing the diverse genetic background in highbush blueberries. Additionally, this study explores cultivar-specific differences in Agrobacterium susceptibility, which remain unexplored in highbush blueberries. Regeneration from leaf explants of 15 highbush blueberry cultivars was investigated on media containing 1.0 mg/L TDZ or 1.0 mg/L TDZ and 0.5 mg/L NAA. There was considerable variation in callus formation and regeneration rates, the number of regenerated shoots, the time required for regeneration, indicating that regeneration in highbush blueberry is highly genotype-dependent. The regeneration rate was high (>75%) in ‘Blue Muffin’, ‘Legacy’, ‘Gulfcoast’ and ‘Georgiagem’. However, ‘Georgiagem’ required three additional weeks for shoot regeneration from the time of meristem formation compared to the other three high regeneration cultivars. All four northern highbush cultivars exhibited low regeneration rates (

Protein phosphatases, particularly PP2C families, are vital regulators of cellular activity through the removal of phosphate groups from proteins. Numerous biological processes, such as hormone signaling, reactions to heat and drought stress, and abiotic stress tolerance, are impacted by this dephosphorylation process. This study presents comprehensive genomic analysis, evolutionary assessment and transcript profiling of the PP2C gene family in sweet potato, a crop of major agricultural and nutritional importance. A total of 74 PP2C genes have been identified in sweet potato. Among them, 7 gene pairs were identified as segmental duplication while 5 pairs as tandem duplications. Phylogenetic analysis grouped them into distinct clusters, indicating potential functional divergence. Gene structure analysis provided insights into the arrangement of coding and non-coding regions. Motif and domain analysis highlighted conserved protein sequences aiding functional predictions. Synteny analysis compared genomic regions across species identifying homologous genes and tracing genome evolution. The study of cis-regulatory elements in promoters helped map gene regulations. Gene expression analysis is currently being conducted to determine the transcript levels of PP2C during salinity and drought stress. The results provide a basis for additional validation of the roles of the PP2C gene in sweet potatoes and advance our knowledge of the evolutionary background and functional significance of PP2C in biotic and abiotic stress response.

A forum for discussion of potential collaborations with regards to technology in horticulture – i.e. biotechnology, UAVs, cameras, sensors, artificial intelligence, etc.

The Technology Applications in Horticulture Interest Group will meet at this session.

The origin of the cultivated strawberry traces to the 1700s, when representatives of the octoploids F. chiloensis and F. virginiana – previously brought to Europe from South and North America, respectively – were grown in proximity in European horticultural gardens. Cross-pollination produced hybrids that were quickly recognized for their unique and desirable combinations of morphological and fruit characteristics and were brought into cultivation and breeding (Hancock 1999). Traditional breeding objectives are the following (Rosati 1993): a production of relatively large berry size in order to limit the cost of harvest, a firmer fruit with regular shape and long shelf life, which is easy to harvest, an increase in the total yield, an improvement in fruit appearance (color, shape, brightness), and disease resistances. The recent origin makes F. ananassa one of the youngest of contemporary crop species. Bottle neck existing in strawberry traditional breeding is that it is difficult to manipulate single genes to control strawberry characteristics, modern genetic transformation and genome editing technology provide promising ways for single gene control in strawberry. Diploid strawberry transformation has been reported, limited report was available for transformation of octoploid cultivated strawberry. We report an efficient Agrobacterium mediated strawberry transformation system with the aid of GFP visual selection. First three open leaves from 4 weeks old in vitro plants were harvested, and leaflets were separated from each other and inoculated with Agrobacterium tumefaciens GAV3101 contains a binary vector with GFP and hygromycin resistance genes. Transgenic callus and shoots obtained with GFP visual selection with high efficiency. PCR double check proved transgenes in transgenic plants. Transgenic plants are phenotyping in the greenhouse.

Flowering plays a crucial role in blueberry production since fruits develop from flowers. In plants, FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1), which interact with the bZIP transcription factor FD, are central regulators of flowering. This study investigates the roles of their homologs in blueberries, VcTFL1 and VcFD, using RNA interference (RNAi) to silence these genes. Two RNAi constructs, VcFD-RNAi and VcTFL1-RNAi, were introduced into the northern highbush blueberry (Vaccinium corymbosum) cultivar ‘Aurora’ via Agrobacterium tumefaciens-mediated transformation. Phenotypic analysis of first-generation (T0) transgenic plants accessed flowering time, architecture, fruit and leaf bud development, plant height, and branching. Preliminary results revealed that VcFD-RNAi plants produced fewer shoots, while VcTFL1-RNAi plants exhibited reduced branching per shoot compared to nontransgenic ‘Aurora’ controls. Significant differences in leaf bud number were also observed between nontransgenic and transgenic lines. VcFD-RNAi plants were smaller than nontransgenic ‘Aurora’ plants, whereas no significant size difference was detected between VcTFL1-RNAi and wild-type plants. Transcriptomic comparisons between nontransgenic ‘Aurora’ and transgenic lines revealed differentially expressed genes (DEGs). The VcFD-RNAi vs. nontransgenic ‘Aurora’ identified 2,108 DEGs, including 49 flowering-related genes, 116 genes hormone pathway genes, and 57 sugar metabolism genes. Similarly, the VcTFL1-RNAi vs. nontransgenic ‘Aurora’ uncovered 2,030 DEGs, with 52 flowering-related, 111 hormone-related, and 55 sugar-metabolism-associated genes. Ongoing analyses of these DEGs aim to elucidate the molecular mechanism underlying VcFD- and VcTFL1-mediated flowering regulation of flowering and development in blueberry. This study will reveal the functional roles of VcFD and VcTFL1, offering potential targets for genetic improvement of blueberry architecture and yield.

Botrytis cinerea is the second most economically important fungal phytopathogen causing gray mold disease. Multiple fungicide-resistant B. cinerea strains have also been reported, especially in strawberries, raspberries, grapes, and tomatoes. RNA interference (RNAi) is a post-transcriptional gene silencing mechanism in all known eukaryotes. The exogenous application of dsRNAs to knock down the target organism's essential genes is called spray-induced gene silencing (SIGS). This non-transgenic SIGS-based approach has emerged as an appealing alternative biofungicide. Despite the great potential of sprayable RNAi-based pesticides, this innovative technology encountered challenges. The low stability and the limited uptake efficiency of dsRNA are significant challenges facing SIGS. Nanomaterials-based delivery systems and structured modification of dsRNA molecules could be innovative SIGS approaches for improving its stability, uptake efficiency, and biofungicidal efficacy. This study aims to develop sprayable RNAi (SIGS) solutions by modifying dsRNA structure and using chitosan-based nanoparticles to control fungicide-resistant B. cinerea. Chitosan nanoparticles (CNPs) were generated using ionic gelation, and different forms of double-stranded RNA (dsRNA), either linear or secondary-structured, were loaded into them. The positive charges from the amine groups present in chitosan facilitated the self-assembly of the CNPs-dsRNA complex through electrostatic attraction. The stability of CNPs-dsRNAs complexes was evaluated ex-vivo by incubating naked-dsRNAs and complex-dsRNAs with the RNase A. Gel retardation assay revealed that CNPs-dsRNA complex of either linear or secondary structured-dsRNAs exhibited substantial protection of dsRNA from RNase A degradation for up to 72 hours, suggesting its potential for improving stability and long-lasting efficacy. The CNPs-dsRNAs significantly reduced the mycelial growth of wild-type and fungicide-resistant B. cinerea isolates. The results from this study indicated that chitosan-based polymer could be an effective delivery technology for both linear and secondary-structured dsRNA and hold great promise for the management of gray mold diseases.

Bacterial wilt (BW), caused by the soil-borne vascular bacterium Ralstonia solanacearum (Rs) species complex (RSSC), is one of the most devastating diseases affecting tomato and many other economically important crops. Rs infection leads to quick wilting and eventually plant death. Unfortunately, tomato bacterial wilt resistance genes have not been identified yet. Our previous study identified a candidate resistance gene from Hawaii 7996, a highly resistant tomato cultivar, that appears to be associated with qualitative resistance to bacterial wilt. Overexpression of the allele from Hawaii 7996 resulted in enhanced resistance in Heinz 1706, a model bacterial wilt susceptible cultivar. Gene editing-assisted gene knockout of the allele in Hawaii reduced bacterial wilt resistance. Yeast two-hybrid assay revealed a potential kinase that interacts with this resistance gene. The identification of the resistance gene and its interacting partner provide a better understanding of the resistance mechanisms and can be used for tomato bacterial wilt resistance breeding.

Manipulating the expression of flowering pathway genes holds potential for regulating tomato fruit productivity. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) is a MADS-box gene that serves as a key integrator in the flowering pathway. In this study, two full-length SOC1 genes cloned from maize (ZmSOC1) and soybean (GmSOC1), along with a partial SOC1 gene from blueberry (VcSOC1K, containing the K-domain), were individually transformed into tomato for constitutive expression. Phenotypically, the expression of VcSOC1K and ZmSOC1, but not GmSOC1, led to early flowering. Most transgenic lines for all three constructs exhibited a significant increase in fruit number per plant. More importantly, compared to non-transgenic plants, all three constructs resulted in varying degrees of increased fruit production per plant, primarily through enhanced branching. At the transcriptomic level, comparative analysis of GmSOC1 revealed the broader impact of the transformed genes. The increased expression of CLF and EZA1 appears to explain the unchanged flowering time of the GmSOC1 transgenic plants, while the repressed expression of DWARF genes likely contributes to enhanced branching. Additionally, numerous genes associated with biotic and abiotic stress tolerance displayed differential expression. These findings demonstrate that constitutive expression of either full-length or partial SOC1 has the potential to enhance tomato fruit production.

Flowering dogwood (Cornus florida) is a native tree species to the Eastern US that is susceptible to powdery mildew fungus. Genetic transformation of somatic embryogenic tissue in conjunction with gene editing are molecular methods used to breed pathogen-resistant cultivars. This research investigates the most effective germination treatment in regenerating plantlets from genetically transformed somatic embryos of flowering dogwood. From somatic embryogenic callus cultures containing the reporter transgene ß-glucuronidase (GUS), we grew tissue in liquid suspension and size fractioned using sterile metal sieves of different pore sizes. We collected pro-embryogenic masses (PEMs) from the small mesh size sieve, plated PEMS onto nylon supports using vacuum, and placed the nylon supports to semi-solid maturation media for embryo development. We chose somatic embryos elongating beyond the torpedo stage with the best quality and appearance and placed them across the four germination treatments. The germination experiments evaluated four different treatment concentrations of four different plant growth regulators (PGRs), gibberellic acid (GA3), abscisic acid (ABA), 6-benzylaminopurine (BAP), and melatonin. The environmental conditions for the first experiment included fluorescent lighting (10 μmol/m²/sec), temperature at 23 ºC (±1), and a photoperiod of 16h light:8h dark. Somatic embryos growing in germination media supplemented with GA3 (1, 2mg/L) had a higher percentage of embryos showing emergence of the apical shoot meristem between the cotyledons. The next highest percentage of somatic embryos with emerging apical meristems occurred using BAP at the concentrations 0.5 and1mg/L. The second germination experiment assessed the same treatments above except used early- stage torpedo somatic embryos and the light intensity increased to 35 μmol/m²/sec. BAP at 0.5 and 1mg/L showed the highest percentage of greening cotyledons and rooting rates. However, in 60 days, all the somatic embryos died in the GA3, ABA, melatonin, and BAP germination treatments. Although we successfully developed healthy transgenic somatic embryos, converting them into plants was a major challenge. The furthest germination stage we reached was the emerging of apical shoots, where the meristem elongates and continues to primary leaf formation. The difficulty in obtaining complete conversion to plants from these transgenic somatic embryos suggests there may be unintended impacts on growth or germination based on the location of the GUS transgene in the genome. Additionally, the original transgenic embryogenic culture was eight years old prior to the germination experiments, which could have influenced embryo conversion to plants.

Spring frost is a major environmental stressor caused by sub-zero temperatures (≤ 0 °C), often accompanied by freezing dew points, and poses a substantial economic threat to fruit crops. While the frequency of spring frost events may be influenced by climate change, the severity of damage has increased in recent years. This is largely due to elevated early spring temperatures that induce precocious bloom, making developing flower buds more vulnerable to subsequent frost events. Although no bloom-delay plant growth regulator (PGR) has been fully established to date, the use of PGRs to postpone flowering and mitigate frost risk remains a highly sought-after strategy in horticultural production. Our previous research demonstrated that fall applications of ethephon can delay bloom by 3–6 days in peach (Prunus persica). However, this treatment has also been associated with severe gummosis, necrosis, and branch damage. In the present study, we employed a plant hormonomics approach to investigate the relative abundance of endogenous hormones in flower buds of ethephon-treated versus untreated peach trees. Our analysis revealed dynamic profiles of abscisic acid (ABA), auxins (e.g., indole-3-acetic acid, indole-3-acetamide, 2-oxo-indole-3-acetic acid), brassinosteroids (e.g., 28-norcastasterone), cytokinins (e.g., zeatin, kinetin, N6-isopentenyladenosine), jasmonate-related compounds (e.g., cis-12-oxo-phytodienoic acid, dinor-12-oxo-phytodienoic acid, jasmonic acid [JA], JA-phenylalanine), salicylic acid, gibberellins (e.g., GA1, GA3, GA4, GA6), and strigolactones, with distinct accumulation patterns related to chilling and heat accumulation during dormancy and in response to ethephon treatment. Among these, jasmonates exhibited a unique pattern: levels remained low during dormancy and spiked sharply near bud break, but this spike was significantly suppressed in ethephon-treated trees. Based on this observation, we hypothesized that JA biosynthetic inhibitors could serve as effective bloom-delay agents. Indeed, over two consecutive seasons (2023 and 2024), we tested two JA inhibitors—propyl gallate and antipyrine—in two peach cultivars, ‘Sunhigh’ and ‘Redhaven’. Both compounds significantly delayed bloom progression compared to untreated controls. Furthermore, in 2025, antipyrine treatment resulted in a marked reduction in flower mortality following a killing freeze, which caused 100% damage in untreated trees versus approximately 90% in antipyrine-treated trees. To the best of our knowledge, this study represents the first hormonomics-driven translational approach aimed at regulating bloom time in perennial fruit trees to enhance their resilience to climate-related frost events.