Brief Summary of Minutes of Annual Meeting

The annual meeting was called to order at 8:30am on 14-Oct-2022. A brief discussion of plans and goals for the meeting ensued after introductions. Dr. Yadegari introduced Dr. Parker Antin (Associate Vice-President for Research (ALVSCE) & Associate Dean for Research (CALS) at the University of Arizona) for welcoming remarks. Dr. Murat Kacira then discussed activities at the Controlled Environment Agricultural Center at the importance of seed research for controlled environments. Researchers gave state reports from 10:15am until 12pm. Emmanuel Gonzalez, a Ph.D. candidate, presented on his research. State reports continued from 1:30-2:30pm.

Dr. Greg Welbaum called the business meeting to order at 2:45pm. Dr. Paul Johnson discussed national program leadership. Dr. Johnson provided advice on structure and format for the upcoming W4168 project re-write. He emphasized the use of lay language when writing impact statements and to reduce the size of project descriptions. Dr. Johnson advised a target submission date of March 2024. The group then discussed how to clarify and broaden current objectives. The group decided to edit objective 1 but leave objective 2 as is. Objective 1 will no read: “Understanding how genetic and environmental mechanisms affect seed processes”. The business meeting concluded at 3:30pm. The group then toured the Controlled Environment Agriculture Facility.

The business meeting resumed on 15-Oct-2022 starting at 8:30am. The group sought volunteers for the re-write committee. Four members agreed to serve on the committee. The group then continued a discussion of the re-write focusing on creating unifying themes such as climate change and ecology since the group membership is shifting. The group discussed recruiting new members given the upcoming wave of retirements. Members discussed the inclusion of extension and outreach activities as outputs. A suggestion was made that members of the re-write committee take on specific objectives to facilitate the process. The group was encouraged to initiate the re-write process during the fall of 2023 utilizing on-line collaboration technologies. The group committed to providing requested information in a timely manner.

Discussion then shifted to identifying a location for the 2023 meeting. The group voted to hold the 2023 meeting in Virginia. Dr. Welbaum will investigate this and report back. Discussion moved on to selecting new officers. Dr. Kawashima agreed to serve as secretary, Dr. Torrion will advance to chair, and Dr. Pérez will serve as vice-chair. Dr. Torrion then assumed leadership as new chair and called for new business. The group was reminded that annual reports are due in 60 days. Dr. Pérez agreed to send members a template that emphasized the Appendix D/SAES-422 format. A suggestion was made to initiate the re-write process during spring 2023. Members also agreed to solicit participation from seed-centric colleagues. The business meeting was then paused to complete state reports.

The business meeting resumed with the creation of a website to be used as a recruitment tool. The new website would have a more graphical format than the text rich NIMSS site. Another goal of the website is to increase visibility of seed biology research conducted across the US. Drs. Kawashima and Torrion on working on the new website. The business meeting was then adjourned.

AZ (Yadegari) – Research was focused on understanding two major questions focused on how drought and mutations that alter basal endosperm transfer layer (BETL) can independently alter endosperm development and consequently the overall kernel size and quality in maize (Zea mays). We analyzed the structure of the maize endosperm and the genes expressed within the whole kernel upon varying lengths of water withdrawal one day after pollination. We have developed a dataset of the gene sets dysregulated under drought conditions. We have also generated mutant combinations in a class of transcription factor genes that are responsible for proper differentiation and function of the BETL. One of these mutant combinations showed a delayed and diminished development of BETL and a concomitant reduction in kernel size and quality. Furthermore, some of the gene sets dysregulated in the BETL mutants are highly similar to those in kernels grown under drought. These data can provide clues as to the nature of biological processes that can be dysregulated within the seed in response to both endogenous and environmental cues.

FL (Pérez) – Small holder farmers in the southeastern US are expressing interest in the practice of saving farm grown seeds from open-pollinated crops that may demonstrate appropriate market demand and regional adaptability. However, adoption of this practice is constrained by a lack of technical expertise related to seed production and biological knowledge underpinning the on-plant development of high-quality seeds and maintenance of post-harvest seed quality. At the same time, natural resource practitioners in the same region struggle to obtain high-quality seeds of wild species necessary for re-vegetation and landscape rehabilitation programs. They report a lack of key information on how various land management practices and prevailing environmental conditions influence seeds quality.

We worked with four small holder, local, farmer collaborators to identify three vegetable and one wildflower crop of interest. We investigated the influence of 1) crop management and seasonal timing on seed development, seed yield, and proportion of filled seeds; 2) seed source (i.e., locally produced vs. international origin) on subsequent crop traits; and 3) post-harvest seed treatments on germination capacity. Likewise, we collaborated with land managers to study how timing of prescribed burns and habitat of origin influenced seed fill, germination capacity, and vigor of wiregrass (Aristida stricta) a keystone bunchgrass of xeric and mesic pine ecosystems.

We discovered that the production of high-quality vegetable and wildflower seeds is feasible despite Florida’s hot, humid climate. Season of planting is crucial. For example, farmers should plant Yukina Savoy (Brassica rapa L. subsp narinosa) in the late fall to obtain healthy, high-quality seeds by mid-spring. Planting Yukina Savoy in the late winter/early spring pushes the seed production window into late spring. However, disease pressure increases considerably at this time as daily humidity and rainfall potential increases. Similarly, cowpea (Vigna unguiculata) should be planted by mid-September rather than June or July to avoid disease pressure that influences seed quality. Production of Bellevue Butternut (Cucurbita moshata) squash seeds does not seem adversely affected by its typical production season.

We found that seed development of the selected vegetable crops is consistent despite considerably different farming practices and crop management. Moreover, we were able to pinpoint optimal widows throughout the seed developmental program that contribute to maximum germination ability, minimum seed moisture content, and resistance to aging stress. Farmers were often interested in collecting seeds early during the developmental program. Nonetheless, we were able to demonstrate the negative impact of early collection on seed quality. We also determined that locally sourced seeds of Yukina Savoy produced plants with better vigor and greater biomass than plants produced from seeds of international origin after one generation of seed production in Florida.

We determined that butterfly milkweed (Aslcepias tuberosa) seed yield was similar between the first and second years of seed production. This plant has the potential to produce > 200,000 seeds per hectare. Growing butterfly milkweed plants in a landscape fabric system to minimize competition from weeds did not diminish seed yields. But producers should avoid shading as this produces 1.2 to 9.6-fold decrease in seed yield depending on duration of shade exposure. Butterfly milkweed has an extended flowering season and produces fruits from June through September. Our research revealed that seed quality, in terms of germination capacity and rate, was better for seeds harvested in July or August rather than September. We also found that butterfly milkweed seeds from plants originating in north-central Florida do not require cold, dry conditions to promote germination. In fact, this often-cited recommendation was detrimental to germination.

Our conversations with farmer collaborators and a formal survey of the wider farming community revealed that many farmers in the region have the intent to enter seed production but lack resources (e.g., financial, technical, informational) to do so. Some farmers also expressed concerns on post-harvest handling and storage of seeds. This makes sense in Florida’s hot, humid climate that is not conducive for seed storage especially for limited resource farmers who do not possess climate-controlled facilities for maintaining seed viability. Our farmer collaborators also indicated that they plan to continue seed production for butterfly milkweed, Bellevue butternut squash, and cowpea. One collaborator mentioned that while seed production of Yukina Savoy is feasible, they would not continue with this crop as it may not match well with their farm management plan. Nevertheless, the same farmer decided to purchase some of the desiccant based seed drying systems that we demonstrated as part of the project.

We observed that habitat of origin and timing of prescribed burn were associated with the amount of seed fill for wiregrass. Seeds collected from a xeric site had the highest proportion of unfilled seeds (64%), while seeds collected from mesic sites displayed lower proportions of unfilled seeds (34-55%). Unconditioned, bulk seed lots of wiregrass sell for $140 per pound. Our economic analysis suggested that at the fill levels represented here as much as $131 out of $140 goes towards unfilled seeds when collections occur from xeric sites compared to $69 out of $140 for collections from mesic sites. We also discovered that plots burned later in the growing season (i.e., July) produced more filled seeds than plots burned earlier in the growing season (i.e., April-May). Interestingly, germination of filled seeds was relatively high (67-73%) across habitat type and burn years. Seeds responded with the highest and most rapid germination following exposure to spring temperatures. Summer and winter temperatures induced the lowest germination responses. This supports the recommendation to sow seeds in spring to facilitate plant establishment. Moreover, wiregrass seeds appear to lose vigor over a few months of lab storage. Therefore, precautions should be taken to ensure proper post-harvest handling

KY (Downie, Geneve, Kawashima) – LEA14, a LATE EMBRYOGENESIS ABUNDANT PROTEIN (LEAP) of the dehydrin family was found to bind ABSCISIC ACID INSENSITVE3 (ABI3) at the B3, DNA binding domain. This interferes with ABI3 action such that seeds from lea14 are ABA hypersensitive while LEA14-OE seeds are ABA hyposensitive. ABI3 upregulates LEA14 thought the single By/Sph motif present in the LEA14 promoter while VIVIPAROUS1/ABI3-LIKE2 (VAL2), another B3 domain protein involved in epigenetic silencing downregulates LEA14 expression. LEA14 also binds VAL2 but not at the B3 domain. Dietary augmentation of the non-reducing sugar trehalose and the osmoprotective amino acid proline in Drosophila melanogaster embryos has been successful. LATE EMBRYOGENESIS ABUNDANT PROTEINs (LEAPs) and additional trehalose is being introduced through sonoporation. Additional lines of D. melanogaster have been generated that express various brine shrimp (Artemia franciscana) LEAPs. Embryos will then be assessed for their ability to withstand partial desiccation and cryopreservation.

Studies were conducted to improve the germination capacity in industrial hemp. Cardinal temperatures for industrial hemp were determined for two accessions and a thermal time model was developed that modeled germination at temperatures between 17 and 25^oC. In addition, parameters for seed priming were developed that could improve stand establishment of field seeded hemp. Also, a physical pericarp removal protocol was developed for improved germination in low germinating seed accessions of industrial hemp. On average, pericarp removal improved final germination in low-germinating seed lots by approximately 38% compared to intact seed germination.

The endosperm within a seed is a tissue that supports embryo development and is a product of fertilization. Endosperm cells undergo nuclear divisions without cytokinesis right after fertilization, generating a large multi-nuclear cell. Cellularization subsequently occurs.The duration of this multi-nuclear endosperm phase is correlated with the final seed size. However, the molecular mechanisms and cellular dynamics by which the endosperm contributes to final seed size remains largely unknown. We have characterized nuclear divisions and movement as well as the role of the cytoskeleton in this unique endosperm development in Arabidopsis thaliana via confocal live-cell imaging technology.

Separately, using soybean as a crop model, we investigated how assimilate supply changes during early seed development and how this affects subsequent seed development. We found that assimilate changes early in seed development plays a critical role in determining maximum seed weight and hence has an influence on seed quality.

IA (Goggi) – Iowa researchers investigated the effects of chemical defoliation on the migration patterns of oil bodies within embryo cells during desiccation. Chemical defoliation of seed corn production fields accelerates seed maturation and desiccation and expedites seed harvest. Early seed harvest is important to minimize the risk of frost damage while in the field. Premature defoliation may interfere with the migration of oil bodies within embryo cells during desiccation and affect seed germination and vigor. This study demonstrated that oil bodies within embryo cells followed normal migration patterns according to seed moisture content, and seed quality remained high, regardless of defoliation treatment. Chemical defoliation is a viable production practice to accelerate seed corn desiccation, and to manage harvest and seed drier availability more efficiently without negatively affecting seed germination and vigor. Likewise, researchers constructed a library of images showing results of biochemical staining assays that tested for maize seed viability after drying. Researchers also explored how seed size and seed density uniformity in a bag of commercial hybrid seed affect seed germination and emergence in the stressful field conditions of a perennial ground cover. This research shed light on farmers’ misconception that variation in seedling emergence is due to disparities in seed size within a bag of seeds. Research findings demonstrated that depth of planting, rather than seed size, is the primary cause of uneven emergence and yield decline in corn.

In a separate study, researchers compared and optimized the original protocol used to detect Pantoea stewartii subsp. stewartii (Pss) in maize seeds. For ground seeds, naturally and artificially contaminated samples were analyzed after purifying the seeds extract. Sensitivity and efficiency were measured by spiking the seed extracts with different levels of the bacterium. A robustness evaluation of the SYBR-PCR was realized. The evaluation included different thermocycler brands, master mix brands, and deviations in annealing temperature. Standard genomic curves of qPCR with cycle threshold (Ct) values vs. 10-fold serial dilutions of Pss strain 9239 purified genomic DNA starting with 10 ng were analyzed. Seed samples with different levels of contamination are being prepared and characterized for an inter-laboratory study. To validate the results, samples will be distributed to two seed industry laboratories and a USDA research laboratory. The team extended the applicability of this technique to detect Pss in treated maize seeds.  It will analyze and summarize the results of the inter-laboratory comparative test and submit the data for approval by the National Seed Health System (NSHS) Technical Review Panel.

The group also conducted experiments to evaluate the interaction of seedling and seed pathogens with seed quality and its effect on soybean emergence and seedling vigor. Seed lots of different seed quality levels were created by accelerated-aging treatments. The effect of aging treatment (AA) on seed performance was tested in growth chambers with and without the seed-borne pathogens. Overall, low quality seeds negatively impacted germination, seedling growth, root weight and volume. A significant interaction was detected between AA treatment and Fusarium graminearum (Fg) inoculation only for root fresh weight, but the effects were not additive or synergistic at 20°C. There were few significant treatment effects at 25°C. Overall impact of Fg inoculation on emergence and seedling health was less than expected, and a heightened susceptibility of AA-treated seeds was not observed. The experiment will be repeated using additional isolates of Fusarium and Rhizoctonia.

Substantial improvements have been made in developing an effective protocol for greenhouse screening of iron deficiency chlorosis and Fusarium root rot using a hydroponics system. This progress paved the way for collaboration with other Iowa State researchers. This study uses a nutrient solution that mimics more closely Iowa’s soils with iron deficiency chlorosis (IDC).

MI (Fleming) – We continued collecting and analyzing data from the 16^th bottle of seeds buried by Dr. William Beal in 1879. Twenty Verbascum seeds germinated, of which one was confirmed by ITS sequencing to be a hybrid of V. thapsus x blattaria, while the remainder were V. blattaria. Beal’s reports only mention V. thapsus, so the source of V. blattaria seeds remains a mystery. Tissue from one V. blattaria, plant 2021-10, was used for whole genome sequencing and assembly. The assembly is currently being refined using transcript We have recovered three intact Verbascum seeds from the germination test and have several other Verbascum seed collections available. We are planning comprehensive experiments to assess the effects of seed storage environment and duration on the germination process. These experiments will include physiological and molecular assays.

MT (Torrion) – We tested sets of hard red winter wheat and soft white winter wheat market classes. The latter is not a popular class of winter wheat despite its higher yield potential compared with the former. Soft white winter wheat tends to be vulnerable to late maturity-alpha amylase activity of the seeds and in a worst-case scenario, to preharvest sprout. We tested irrigation management via surface drip tape in environment 1 such as 1) no stress (100 percent evapotranspiration, 100ET), 2) following 100ET but the final irrigation was at flower, 3) 100ET but final irrigation at milk, 4) deficit irrigation at 66% ET [66ET], and a 5) rainfed check.

Environment 2 followed the same protocol as Environment 1 but with rainfall simulation within the grain-filling stage using a center pivot overhead sprinkler. We found that continuous application of irrigation beyond the flowering stage causes a lowering of falling numbers – an indicator test for increased amylase activity regardless of wheat type. Also, the continuous wetting of wheat heads via the simulated rainfall events during the grain-filling stage increased amylase activity by 10%. Reducing amylase activity, especially in soft white winter wheat, which is more vulnerable to amylase activity than hard red winter wheat, is done by terminating irrigation management at the flowering stage. For either of the market classes, continuous irrigation after flower either at 100ET or at deficit level did not improve yield or seed quality.

NY (Taylor) – New tools are needed for weed management especially during the Critical Weed Free Period (CWFP) of crop development. The CWFP is the time where interspecific competition must be reduced to maximize yield production, usually the first few weeks following crop emergence. One approach is to develop imaging technologies to recognize and differentiate between crop and weed seedlings to facilitate precision weed management. Hemp (Cannabis sativa) was chosen as the model crop as weed control options, particularly herbicide availability, are limited in the US. Our approach was to use fluorescent tracers, applied as either seed or soil treatments, which are taken up by hemp seedlings. Rhodamine compounds have a desired optical property that both absorbs light and fluoresces in the visible range, so conventional illumination sources and imaging sensors can be used to excite and detect the unique fluorescence in the lab and field. A prototype fluorescence imaging system with needed algorithms and graphic user interface (GUI) was developed at Cornell AgriTech for data acquisition and analysis for lab testing.

The selectivity of rhodamine, fluorescent tracers was tested in a crop/weed competition study in growth chamber studies. Rhodamine was applied as a seed treatment or soil applied at time of planting. Velvetleaf (Abutilon theorphrasti) was used as the model weed. Velvetleaf was selected for use in this study as it is a common weed throughout many hemp growing regions of the US. Velvetleaf seeds were planted 2.5 cm from the treated hemp seed. Fluorescence was detected only in the crop seedlings when rhodamine was applied as a seed treatment; conversely, some fluorescence was observed in the velvetleaf seedlings from a soil application.

OR (Elias) – The seed group at Oregon State University conducted studies in both basic and applied research. The two broad objectives of the current W4168 project that we focused on are:  1) Understand how developmental and environmental mechanisms affect seed quality, and 2) Capitalize on new technologies to assess and manipulate traits to enhance seed quality. Dr. Hiro Nonogaki and his group studied seed dormancy, germination, and pre-harvest sprouting. Dr. Thomas Chastain and his group studied the effect of plant growth regulators on improving yield of grass species and other crops. Dr. Sabry Elias and his group studied seed quality, bio-enhancement, and storability in hemp; the effect of using high temperatures on the quality of coated seeds; and bioassay methods to screen winter wheat for quizalofop herbicide tolerance. Several practical applications and recommendations to growers have been generated from our research projects. Numerous multistate activities involved stakeholders and seed industry, as well as conference presentations that have been delivered. Several papers have been published or under review on these subjects.

SD (Gu and Latvis) – The first set of preliminary experiments were conducted to evaluate effects of GA signaling genes on seed dormancy. All three GA signaling gene, Slr1/slr1, Gid1/gid1 and Gid2/gid2, were associated with the degree of primary seed dormancy and germination velocity in seed populations segregating for each of the loci. To determine if any of the GA signaling genes interact(s) with seed dormancy (SD) genes cloned from weedy rice, we developed three F2 populations, each containing allelic variants at the all four seed dormancy (SD) loci, SD1-2 (A/a), SD7-1 (B/b), SD7-2 (C/c), and SD12 (D/d), and the alleles at one of the Slr1/slr1, Gid1/gid1 and Gid2/gid2 loci. Each of the F2 populations was grown in a greenhouse, evaluated for plant and leaf morphologies, flowering time, and seed dormancy by germination testing. Large variations for the morphological, flowering and germination traits were detected in each of the three F2 populations and quantitative genetic analyses for the traits were completed. We are genotyping the populations for the dormancy and GA genes using the gene-based markers. The phenotypic and genotyping data will be used to partition the phenotypic variation in seed dormancy in main (additive and dormancy) and epistatic effects of the SD and GA genes using a two-/three-gene model.

The second set of experiments were conducted to evaluate pleiotropic effects of the red pigmentation gene Rc and the purple pigmentation gene Pb on seed flavonoid chemicals, dormancy, and germination. The allelic variants of the Rc/rc and Pb/pb loci were introduced into the same genetic background to identify developmental patterns of the red and purple pigments and to model the pleiotropic effects of the two genes. Experimental data revealed that the two pigment systems differ in morphological and histological patterns during the seed development, Rc had a greater effect on seed dormancy than Pb, and both genes also involve in the regulation of germination speed.

And the third sets of experiments were conducted to advance on-going project to improve the resistance to pre-harvest sprouting (PHS) and germination ability of hybrid seeds using seed dormancy genes. A total of 120 F3 or F4 lines were planted in a field, evaluated for agronomic traits, and sampled seeds to evaluate genotypic difference in the degree of seed dormancy. Elite F4 lines were selected for the next experiments.

Through the Native Plant Initiative at South Dakota State University (SDState), we are raising awareness of native plant species and conducting research on patterns of smoke-induced germination, as well as other traits that improve seeding germination and survival. We have scaled up our sampling of smoke-induced germination responses with a global literature synthesis, which now includes 1256 species. To understand evolutionary patterns for this global dataset, we generated a new phylogeny and conducted Ancestral State Reconstruction analyses, tests for phylogenetic signal (D statistic for binary trait data), and tests for character correlations using evolutionary modeling approaches (e.g. BiSSE and HiSSE; binary and hidden state speciation and extinction, respectively). We find that with much improved sampling, some clades show strong evidence of clustering for this germination response (e.g. Ericaceae), while others do not (e.g. Asteraceae).

In another study, we examined spatial patterns in awn development and correlation with other plant traits. We leveraged digitized herbarium records to address the invasion history and trait variation in Japenese stiltgrass (Microstegium vimineum). Awns are either present or absent in Japenese stiltgrass throughout its native and invaded ranges. We coded awn presence/absence for all georeferenced records, as well as floret length, floret width, and awn length/angle. We also conducted genomic analyses using inter-simple repeat sequencing of 51 samples from 31 populations across the US to understand colonization history of this invasion. Our results show similar patterns of awn polymorphism in the native and invaded ranges, with the awned form significantly predominating at higher latitudes and the awnless at lower latitudes. Awned forms had significantly longer florets than awnless forms. Both herbarium records and genomic data suggest initial introduction and subsequent spread of the awnless form in the southeastern US, followed by a secondary invasion and spread of the awned form stemming from eastern Pennsylvania. Population structure analyses revealed that awned and awnless forms are highly genetically distinct but with some evidence of admixture. This work elucidates a key trait (the awn) helping northern forms of Japanese stiltgrass gain a foothold in colder climates. This strong geographic pattern of awn polymorphism in Japanese stiltgrass is the only case where such a north-south, awned-awnless pattern has been documented in grasses, allowing us to hypothesize that awn-facilitated diaspore burial provides protection from freezing temperatures.

We have also been mapping commercially available seed sources for prairie species used in restoration and calculating phylogenetic diversity levels for different seed mixes. This information will be used to create 480 experimental plots to assess the influence of species richness, phylogenetic diversity, and genetic diversity (i.e. seed source) on soil health and pollinators.

TX (Leskovar) – This year we conducted six studies: 1) Determining the potential of plant bio-stimulants to enhance seedling growth in pepper when applied as a pre-transplant treatment in the rooting media, 2) Determining the impact of solid humic substance and LED light quality on tomato transplants, 3) Evaluating the impacts of grafting on tomato thermotolerance, 4) Investigate the influence of wild-relative tomato rootstocks on grafted tomato thermotolerance, 5) Determining the impact of bio-stimulants to enhance onion and artichoke seedling growth, stand establishment and yield, and 6) Determining the effectiveness of humic substance applications on ameliorating drought and salinity stress in spinach. Additionally, we have initiated another ongoing experiment (7) focused on improving the iron nutrition of hydroponic leafy greens cultivated at high pH.  Findings from these studies are intended to provide recommendations to small-scale growers to enhance their profits and contribute to the sustainable production of high value vegetable crops.

We completed our second trial of pepper responses to transplant stage bio-stimulant amendments, in which four different bio-stimulants (two humic acids, calcium spray, Trichoderma) were applied at the seedling stage to 'Mama Mia Giallo' and 'Tenor' pepper cultivars. Root and shoot parameters were measured through destructive means. Results revealed that Novihum- (solid humic acid) treated “Mama Mia Giallo’ seedlings had higher relative root growth rate and greater leaf area compared to control plants. Overall, Novihum-treated seedlings outperformed other seedlings in most shoot and root parameters one month after seeding. The results imply that humic substance amendments can aid in seedling vigor by modulating their root and shoot growth whereas calcium spray and Trichoderma resulted in poor plant performance demonstrating their lack of beneficial effect.

In addition, we are conducting a study on the use of commercial microbial bio-stimulants added to media to produce organic pepper transplants. Products containing a multiple species blend of plant growth promoting Rhizobacteria (PGPR) and other beneficial plant growth promoting microorganisms are being tested on two varieties of pepper. Early results show that a blend of PGPRs added with mycorrhizae has superior performance in producing organic pepper transplants. The seedlings are now being grown in a greenhouse with organic practices to assess post-transplant effects.

Our growth chamber study identified significant benefits of solid humic substance as a soil amendment in round ‘Celebrity’ and cherry ‘Chadwick’ tomato transplants under different LED light environments (fluorescent, 10B-90R, 50B-50R, 100B). At five weeks after sowing, seedlings treated with humic substance had three to five folds higher shoot and root biomass and leaf area than the controls. This led to a significantly higher early fruit harvest of ‘Celebrity’ tomatoes in humic substance treatment plants in high tunnel, while there were no significant treatment differences in total yield of both cultivars after three months of harvesting. LED light with 50B-50R ratio enhanced leaf chlorophyll content and root growth traits, while fluorescent light had the highest leaf area among the light treatments. There were no significant LED quality effects on tomato fruit yield, but humic substance enhanced the yield of ‘Chadwick’ tomatoes in 50B-50R and 100B LED treatments.

A heat stress study was conducted using ‘Maxifort’-grafted tomato seedlings in a growth chamber under a stress (38/30°C, day/night) and recovery period (26/19°C). After 14 days of heat stress, ‘Maxifort’-grafted plants had higher leaf carotenoid:chlorophyll ratio and total soluble protein content than the controls. Antioxidant enzyme activities were selectively regulated under heat stress that ‘Maxifort’-grafted plants had higher leaf ascorbate peroxidase, root superoxide dismutase and catalase, although the beneficial traits did not lead to a significant alleviation of heat stress.

We examined the use of tomato wild relative rootstocks (S. pennellii, S. peruvianum) to enhance the thermotolerance of tomato plants in a growth chamber. The grafted seedlings were exposed to heat stress (38/30°C) for 21 days and compared with self-grafted and ‘Maxifort’-grafted plants. Seedlings grafted onto S. peruvianum showed tolerant heat responses with higher enzymatic and non-enzymatic antioxidant capacity compared to other rootstock treatments. On the other hand, S. pennellii-grafted plants showed susceptible antioxidant enzyme activities under heat stress. Both wild relative rootstock groups had higher leaf chlorophyll content, chlorophyll fluorescence and net photosynthetic rate under heat treatment than self-grafted and ‘Maxifort’-grafted plants, but the low graft compatibility between wild rootstock and cultivated scions led to their poor plant biomass.

Our team has begun a new project investigating the capability of a broad suite of plant bio-stimulants to improve the transplant growth and mature yield of onions and artichokes. In our initial experiment, we applied manufacturer recommended rates of a beneficial bacterial powder, mycorrhizal powder, combined bacterial and mycorrhizal powder, seaweed extract, and humic substance as soil amendments prior to seeding artichokes (’17-111’ and ’17-169’) and onions (‘Cirrus’, ‘Don Victor’, ‘Sofire’) in cell trays. One month after seeding, we photographed trays to quantify transplant stand heights and to estimate total emergence. Additionally, we have taken seedling samples for leaf area, leaf SPAD, root system physical parameters, and plant dry weight measurements. While this analysis is ongoing, we have observed visual differences, such as improved growth of transplants treated with the seaweed extract and humic substance, and improved emergence in artichoke trays treated with the combined microbial-mycorrhizal powder. We plan to transplant the remaining seedlings into the field at Uvalde, TX where we will cultivate them under standard management conditions and assess their changes in growth and eventual marketable yield, to assess any carryover effects of the pre-seeding applications. Seeding stage bio-stimulant applications are uncommon for onion and artichoke producers; by demonstrating the potential for improved growth and yield from use of these bio-stimulants we hope to improve the productivity and profitability of these crops.

Lastly, we have initiated a new, ongoing study examining the leafy green response to different chemical forms of iron fertilizers when cultivated under high pH conditions. Iron deficiency resulting from high pH is a major challenge in hydroponics production, and its prevention at the post-transplant seedling stage is crucial to maximizing production. When iron is added in its cationic form, it reacts with various anions, forming insoluble compounds which are unavailable to crops. Iron chelates are frequently used to supply iron to crops as the chelates surround the iron ions making them stable in solution by preventing their reaction with anions. However, chelates are often unstable under high pH, necessitating their screening for suitability for high pH conditions. Our new study aimed to investigate the effectiveness of three synthetic chelators and fulvic acid, a plant biostimulant with chelating ability, on iron bioavailability for lettuce and kale grown in NFT and deep-water hydroponics under high pH conditions.

Drought and salinity are two major abiotic stresses restraining crop growth and productivity worldwide, and the area affected by these two stresses is increasing. Using a gravimetric platform (Droughtspotter, Phenospex, Netherlands), we examined how humic substance improves spinach's (‘Seaside’) tolerance to the combined abiotic stresses right after transplant. Plants were exposed to either weekly applications of saline solution, restrained irrigation, a combination of the two or exposed to no stress conditions. Additionally, plants were either treated with a 1% v/v solid humic substance soil amendment or none at all.  Irrigation as automatically performed by the gravimetric platform, which also logged the amount of irrigation applied and individual pot weights every 10 minutes. Plants were harvested after one month of growth and measured for physical dimensions and nutrient contents. Initial analysis of the water use data obtained from the gravimetric platform and plant weights demonstrated that humic substance treatments induced greater water use in spinach but improved their water use efficiency. Overall, humic substances improved spinach growth and water use efficiency, subsequently enhancing their abiotic stress tolerance.

VA (Welbaum) – Virginia Tech MS student, Austin King completed a project studying halophyte establishment by transplanting or direct seeding as a strategy to remediate roadway deicing salt runoff into adjacent ecosystems, 2) In collaboration with colleague Bingyu Zhao at Virginia Tech, we demonstrated that virus-induced gene silencing can be used as a tool for studying gene-for-gene pathogenicity/resistance of bacterial fruit blotch disease of cucurbits, 3) Virginia Tech Intellectual properties has patented our natural chemical seed treatment that can kill cultures of the international disease Acidovorax citrulli and on artificially inoculated seeds, 4) Virginia Tech MS student, Michael Beall, studied seed germination of the invasive grass species, Arthraxon hispidus, which can rapidly colonize new areas because it does not exhibit seed dormancy and germinates quickly (<36 hours at 30℃) over a range of conditions. Its thick vegetative ground cover decreases competition and prolific seed development aids establishment.  To further its invasive advantage, germination occurs across a range of salinities. This trait may promote recruitment into salt-stressed environments such as roadsides and tidal ecosystems.

Mechanical control may be effective for controlling A. hispidus. Since seed bank longevity seems unlikely. Mowing before seed maturity will reduce abundance in the subsequent seasons. Evidence is mounting that this species has potential to become a globally pervasive non-indigenous species. With new populations of A. hispidus observed each year, it is seemingly only a matter of time before it spreads across the US and Canada, 5) Xiaoying Li has continued her Ph.D. research on edamame seed quality and seedling disease resistance. Seeds of grain and edamame soybeans were produced in the same field, processed, and stored under the same conditions before germination performance was compared. The optimal temperature range for edamame seedling emergence was 25-32℃, lower than grain-type soybean cultivars (29-36℃). Edamame soybean did not emerge at below 4℃ its apparent base temperature but may have higher tolerance to lower temperatures than grain soybean genotypes. Disease screening is produced promising lines resistant to Rhizoctonia spp.

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Barrett CF, Huebner CD, Bender ZA, Budinsky TA, Corbett CW, Latvis M, McCain MR, Motley M, Skibicki SV, Thixton HL, Santee MV, Cumberledge AN. 2022. Digitized collections elucidate invasion history and patterns of awn polymorphism in Microstegium vimineum. American Journal of Botany 109(5): 689-705.

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Li X, Strawn L, Huang H, Yin Y, Rideout S, Welbaum G, Duncan S, Mille R, Li S, Zhang, B. 2022. Edamame in Virginia III. Handling and Processing from Harvest to Package. Virginia Coop. Ext.

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