Domestic production of culinary herbs continues to increase in the United States. Culinary herbs are primarily propagated by seed; however, some herbs have poor germination rates and slow growth. Thus, there are advantages of propagating herbs by vegetative stem-tip cuttings as they lead to true-to-type plants and a shortened production time. Previous research of ornamental young plants and finished culinary herbs have shown a reduction in rooting time and increases in plant quality with increases in the photosynthetic daily light integral (DLI). To our knowledge, little to no research has addressed how the DLI influences culinary herb liner quality. Therefore, the objectives of this study were to quantify morphological traits of five economically important culinary herbs when grown under DLIs ranging from 2.8 to 16.4 mol·m−2·d−1. Stem-tip cuttings of Greek oregano (Origanum vulgare var. hirtum), rosemary ‘Arp’ (Rosmarinus officinalis), sage ‘Extrakta’ (Salvia officinalis), spearmint ‘Spanish’ (Mentha spicata), and thyme ‘German Winter’ (Thymus vulgaris) were excised from stock plants and rooted under no shade or aluminum shading of 36%, 56%, or 76% to create a range of DLI treatments. After 9 days (spearmint) or 16 days (all other genera) of DLI treatments, the root, shoot, and total dry mass of all culinary herb liners generally increased by 105% to 449%, 52% to 142%, and 82% to 170%, respectively, as the DLI increased from 2.8 to 16.4 mol·m−2·d−1 or genus-specific DLI optimums. Stem length of oregano, spearmint, and thyme decreased by 37%, 28%, and 27%, respectively, as the DLI increased from 2.8 to 16.4 mol·m−2·d−1. However, stem length of rosemary and sage were unaffected by the DLI. The quality index of all genera was greatest at DLIs from 10.4 to 16.4 mol·m−2·d−1. Furthermore, all culinary herbs grown under a DLI of ≤6 mol·m−2·d−1 had low root and shoot dry mass accumulation; and oregano, spearmint, and thyme were generally taller. Therefore, DLIs between 10 to 12 mol·m−2·d−1 should be maintained during culinary herb propagation, because a DLI ≥16 mol·m−2·d−1 may be deleterious and energy inefficient if supplemental lighting use is increased.
Annika E. Kohler and Roberto G. Lopez
Prabin Tamang, Kaori Ando, William M. Wintermantel, and James D. McCreight
Cucurbit yellow stunting disorder virus (CYSDV) is a devastating viral disease of melon that can cause significant yield and quality losses. This disease has recently emerged as a major concern in the southwest United States and major melon-growing regions across the world. Coinfection of melon by Cucurbit chlorotic yellows virus (CCYV) was recognized in Imperial Valley and neighboring production areas of California and Arizona in 2018, but its importance remains largely unknown. Identifying and deploying CYSDV resistance from elite germplasm is an economical and effective way to manage the disease. A F2:3 population was developed from a cross of susceptible ‘Top Mark’ with CYSDV-resistant PI 313970, which was shown to possess a single recessive gene for resistance to CYSDV. The F2:3 population was phenotyped in the field in response to natural, mixed infections by the two viruses, CYSDV and CCYV in the Fall melon seasons of 2018 and 2019. Phenotypic data (foliar yellowing) from both years were not useful for mapping CYSDV resistance quantitative trait loci (QTL), as PI 313970 and CYSDV-resistant F2:3 plants exhibited yellowing symptoms from CCYV coinfection. QTL analysis of the relative titer of CYSDV calculated from reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) data identified one locus on chromosome 3 at the physical location of S5-28,571,859 bp that explained 20% of virus titer variation in 2018 but was undetected in 2019. A locus on chromosome 5 between S5-20,880,639 to S5-22,217,535 bp explained 16% and 35% of the variation in CYSDV titer in 2018 and 2019, respectively. One or both of the markers were present in six of 10 putative melon CYSDV resistance sources. Markers flanking the 2019 QTL were developed and can be used in marker-assisted breeding of CYSDV-resistant melons.
Paul M. Lyrene
Vaccinium stamineum (deerberry) is a highly variable diploid species in section Polycodium. Deerberry is native on excessively drained sandy soils from southeastern Ontario, south through the Florida peninsula to Lake Okeechobee, west to eastern Texas and southeastern Kansas. The V. stamineum used in this study were tall plants (2–4 m) native in north Florida, with a plant architecture similar to rabbiteye blueberry (V. virgatum). Starting in 2013 with crosses between tetraploid highbush cultivars (section Cyanococcus) and colchicine-doubled V. stamineum, hundreds of F1 and thousands of later-generation seedlings were grown and evaluated in high-density field nurseries at Citra in North Florida. The populations studied included F1, F2, backcrosses to each parent species, and BC1 × BC1 seedlings. The goal of the study was to assess the feasibility of introgressing into highbush blueberry cultivars desirable traits from V. stamineum (drought tolerance, red-flesh berries, new flavor components, open flowers with short corolla cups and exserted anthers and stigmas) without introducing horticulturally problematic characteristics (bitter skin, berries that shatter when ripe, difficult vegetative propagation). Vigor averaged very low in F1 seedlings, higher in F2 seedlings and in seedlings from backcrosses to V. stamineum, and highest in seedlings from backcrosses to highbush. Most crosses yielded numerous plump seeds, but crosses to produce F1 hybrids yielded fewer than 10% as many seeds as highbush × highbush crosses. Most vegetative, flower, and fruit traits that differentiate highbush from V. stamineum were intermediate in F1 seedlings. Backcross seedlings more closely resembled the recurrent parent. Variability in morphological characters was high in every generation, giving much opportunity for selection. Some seedlings from backcrosses to highbush (≈5%) appeared to have the vigor, berry quality, and yield potential required in commercial cultivars. Producing highbush cultivars that strongly express a particular V. stamineum trait might best be accomplished by growing large, segregating F2 populations from which parents for backcrosses can be selected.
Orlando F. Rodriguez Izaba, Wenjing Guan, and Ariana P. Torres
Cucumber (Cucumis sativus) is one of the most important vegetables produced and consumed in the United States. In the midwestern United States, a major obstacle to spring cucumber production is low soil temperatures during plant establishment. High tunnel is a popular tool for season extension of vegetable production. Low soil temperature is a challenge for cucumber production even inside high tunnels. Grafting is a cultural practice known to help control soilborne diseases and improve plants’ tolerance to abiotic stresses. Recent studies found that using grafted cucumber plants with cold-tolerant rootstocks greatly benefited early-season seedless cucumber production in high tunnels. The objective of this study was to analyze the economic feasibility of growing grafted cucumber in high tunnels. A comparison of partial costs and returns between growing grafted and nongrafted cucumbers in a high tunnel in Vincennes, IN, was conducted. Data were used to develop a partial budget analysis and sensitivity tests. Data included production costs, marketable yield, and price of cucumber through different market channels. This study provided a baseline reference for growers interested in grafting seedless cucumber and for high tunnel production. Although costs of grafted transplants were higher, their yield and potential revenue helped to offset the higher costs. Results indicated that grafting can help farmers increase net returns through the increasing yield of grafted plants. Results from the sensitivity analysis illustrated how the increased yield of grafted cucumbers offsets the extra cost incurred in the technique while providing a higher revenue. While actual production costs for individual farmers may vary, our findings suggested that grafting can be an economically feasible tool for high tunnel seedless cucumber production.
Tran Kim Ngan Luong, Frank Forcella, Sharon A. Clay, Michael S. Douglass, and Sam E. Wortman
Abrasive weeding is a nonchemical weed control tactic that uses small, gritty materials propelled with compressed air to destroy weed seedlings. Organic fertilizers have been used successfully as abrasive grits to control weeds, but the goal for this study was to explore the effects of fertilizer grit, application rates, and background soil fertility on weeds, plant available nitrogen (N) uptake, and crop yield. Field trials were conducted in organic ‘Carmen’ sweet red pepper (Capsicum annuum) and organic ‘Gypsy’ broccoli (Brassica oleracea var. italica) and treatments included organic fertilizer grit (8N–0.9P–3.3K vs. 3N–3.1P–3.3K), grit application rates (low vs. high), compost amendments (with and without), and weedy and weed-free controls. Weed biomass was harvested at 84 days and 65 days after transplanting for pepper and broccoli, respectively. Simulated total plant available N (nitrate + ammonium) uptake was measured with ion exchange resin stakes between 7 and 49 days after the first of two grit applications. Produce was harvested at maturity, graded for marketability, and weighed. The higher grit application rate, regardless of fertilizer type, reduced the weed biomass by 75% to 89% for pepper and by 86% to 99% for broccoli. By 5 weeks after the first grit application, simulated plant N uptake was greatest following grit application with the 8% N fertilizer, followed by the 3% N fertilizer, and lowest in the weedy control. The high grit application rate of 8% N fertilizer increased pepper yield by 112% compared with the weedy control, but it was similar to that of the weed-free control. Broccoli was less responsive to abrasive grits, with yield changes ranging from no difference to up to a 36% increase (relative to the weedy control) depending on the application rate and compost amendment. This is the first evidence indicating that the nutrient composition of organic fertilizer abrasive grits can influence in-season soil N dynamics, weed competition, and crop yield. The results suggest that abrasive weeding technology could be leveraged to improve the precision of in-season fertilizer management of organic crops.
Tian Gong, Xin Zhao, Ashwin Sharma, Jeffrey K. Brecht, and James Colee
Interest is growing among small-scale growers in grafting tomato (Solanum lycopersicum) for improved crop productivity. Healing of newly grafted plants is often considered to be a critical process requiring a highly controlled environment. Setting up healing chambers and managing healing conditions can be major challenges for small-scale producers that limit graft survival and discourage further attempts at using grafting technology. Here, we demonstrate a simple “chamberless healing” strategy for grafted tomato plants using regular indoor conditions without the need to install and manage a sophisticated healing chamber. We hypothesize that tomato can form a high-quality graft in a healing environment with relative humidity below 70% and ambient temperatures between 22 and 25 °C. ‘Tribute’ beefsteak tomato as the scion was grafted onto ‘Estamino’ rootstock in the 2018 experiment, whereas ‘Multifort’ and ‘Shield RZ F1 (61-802)’ were used as the rootstocks in the 2019 experiment. After grafting, the seedlings for the chamberless healing treatment were kept in uncovered seedling trays and misted with water two or three times per day. Seedlings in other treatments were placed in a humidity dome or wrapped chamber to maintain high humidity during the first few days after grafting. In the 2018 experiment, chamberless healing was compared with covered treatments with different ventilation times during the first few days after grafting. In the 2019 experiment, chamberless healing was compared with a standard graft healing chamber treatment to further validate its feasibility. In both 2018 and 2019, all treatments showed high graft survival rates (>85%) at 21 days after grafting (DAG), and plants from the chamberless healing treatment had a lower incidence of adventitious root growth than plants from other healing treatments (0% to 7% vs. 33% to 78%). In the 2019 experiment, no differences in graft union strength, photosynthetic rate, biomass accumulation, or flowering time were observed between the chamberless and standard healing treatments. Plants with chamberless healing were slightly (8%) shorter than the standard treatment at 21 DAG, but no difference was observed at 27 DAG. Although some additional management is required during healing to prevent water loss, the alternative chamberless system assessed in this study exhibited great potential to facilitate small-scale graft healing for producing grafted tomato transplants under standard indoor conditions without any sophisticated healing environment and management.
Asmita Nagila, Brian J. Schutte, Soum Sanogo, and Omololu John Idowu
When applied before crop emergence, soil amendments with mustard seed meal (MSM) control some weeds and soilborne pathogens. MSM applications after crop emergence (herein “postemergence applications”) might be useful components of agricultural pest management programs, but research on postemergence applications of MSM is limited. The overall objective of this investigation was to develop a method for postemergence application of MSM that does not cause irrecoverable injury or yield loss in chile pepper (Capsicum annuum). To accomplish this objective, we conducted a sequence of studies that evaluated different MSM rates and application methods in the greenhouse and field. For the greenhouse study, we measured chile plant photosynthetic and growth responses to MSM applied postemergence on the soil surface or incorporated into soil. For the field study, we determined chile pepper fruit yield responses to MSM applied postemergence using a technique based on the method developed in greenhouse, and we confirmed that the MSM rates used in our study (4400 kg·ha−1 and 2200 kg·ha−1) inhibited the emergence of the weed Palmer amaranth (Amaranthus palmeri) and the growth of the pathogen Phytophthora capsici, which are common problems in chile pepper production in New Mexico. Greenhouse study results indicated that MSM at 4400 kg·ha−1 spread on the soil surface caused irrecoverable injury to chile pepper plants; however, chile pepper plants were not permanently injured by the following three treatments: 1) MSM at 4400 kg·ha−1 incorporated into soil, 2) MSM at 2200 kg·ha−1 spread on the soil surface, and 3) MSM at 2200 kg·ha−1 incorporated into soil. For the field study, postemergence, soil-incorporated applications of MSM at 4400 kg·ha−1 suppressed emergence of Palmer amaranth by 89% and reduced mycelial growth of Phytophthora capsica by 96%. Soil-incorporated applications of MSM at 2200 kg·ha−1 suppressed emergence of Palmer amaranth by 41.5% and reduced mycelial growth of Phytophthora capsica by 71%. Postemergence soil-incorporated applications of MSM did not reduce chile pepper yield compared with the control. The results of this study indicated that MSM applied after crop emergence and incorporated into soil can be a component of pest management programs for chile pepper.
Mary Hockenberry Meyer, Cydnee Van Zeeland, and Katherine Brewer
Chinese silvergrass (Miscanthus sinensis) is native to East Asia and South Africa and has been grown as an ornamental in the United States for over 100 years. Chinese silvergrass is on the invasive species list for 12 states in the United States and is regulated for sale in New York state. It is often found along roadsides in middle-Atlantic states and Long Island, NY. In 2019 and 2020, we sowed chinese silvergrass seed harvested in Fall 2002 and Spring 2003 from several locations in North Carolina where it had naturalized and from the Minnesota Landscape Arboretum, Chaska, MN. The seed had been stored in a seed storage vault (4 °C) from 2002 to 2020. Germination in 2003 showed variation between 53% to 95% from 19 different individual plants. This same seed when resown in 2019 and 2020 had much lower germination that could be divided into three categories: no germination (five plants), germination of 1% or less (seven plants), and germination of more than 2% (seven plants). Results from this study show that seed viability may be a long-term problem in locations where chinese silvergrass has naturalized.
Evan Elford, Jim Todd, Peter White, Rachel Riddle, John O’Sullivan, and Rene Van Acker
To foster development of Ontario commercial tigernut (Cyperus esculentus var. sativus) production, this study was conducted to identify cultural management practices that increase tuber yields. The agronomic practices of field preparation (hilled vs. not hilled), regular irrigation vs. natural rainfall, varying rates of nitrogen (N) fertility, and early season weed management were evaluated. Irrigation had no significant impact on total fresh weight, dry weight, and marketable yield over 2 growing seasons. Similarly, yields from plants grown in hilled rows vs. flat beds over two seasons showed no significant differences. Tigernut yields did not show a response to increasing rates of N up to 150 kg·ha−1. A critical weed-free period of 3 weeks resulted in an 844% yield increase over the nonweeded control. Overall, the results indicate that in general, tigernut requires few inputs to produce a viable commercial yield under Ontario growing conditions.
Jianyu Li, Xin Zhao, Gabriel Maltais-Landry, and Bodh R. Paudel
Sunn hemp (Crotalaria juncea L.), as a summer leguminous cover crop, is often grown before fall planting of strawberries (Fragaria ×ananassa Duch.) in Florida. Although sunn hemp has been suggested as a green manure for supplying nitrogen (N) to subsequent crops, limited information is available regarding the contribution of sunn hemp biomass to soil N availability in Florida sandy soils with low levels of organic matter. This is especially true for organic strawberry production where nutrient management remains one of the major yield-limiting factors. This study was conducted in Citra, FL, and assessed the dynamics of N availability after soil incorporation of sunn hemp in organic strawberry production systems established on sandy soils in a subtropical environment. Sunn hemp was planted at a seeding rate of 44.9 kg·ha−1 on 19 July 2017 and 24 July 2018 and terminated 65 days after seeding; a summer weedy fallow was used as the control. Containerized strawberry seedlings of Sweet Sensation® ‘Florida127’ were transplanted on 13 Oct. 2017 (22 days after sunn hemp incorporation) and 4 Oct. 2018 (8 days after sunn hemp incorporation). Immediately after sunn hemp incorporation, anion exchange membranes (AEMs) were buried in the soil to monitor soil NO3-N fluxes, together with traditional soil testing to measure extractable soil NO3-N concentrations. In the 2018 season, soils incorporated with sunn hemp residues were also incubated in the laboratory at 24 °C over 8 weeks to determine the N release pattern by quantifying soil NO3-N and NH4-N. Overall, nitrate fluxes monitored by AEMs in the first 3 weeks after sunn hemp incorporation were significantly higher in the sunn hemp treatment than in the weedy fallow control (by 66% to 185%) in both years. Sunn hemp incorporation also led to a considerable increase in extractable soil NO3-N concentration (by 20% to 94%). The early and fast release of plant available N (PAN) from sunn hemp residues was confirmed by the 8-week laboratory incubation study, which demonstrated that the net N mineralization rate of sunn hemp remained highest over the first 2 weeks of the incubation period. Sunn hemp showed a positive impact on organic strawberry early-season fruit yield in both years, with significant increases in marketable (by 59%) and total (by 52%) fruit weight yields and marketable fruit number (by 46%) in 2017 and total fruit number (by 15%) and weight yield (by 14%) and marketable fruit number (by 13%) in 2018. Given the typical waiting period between sunn hemp residue soil incorporation and strawberry planting as well as the lag in nutrient uptake shortly after transplanting, a large fraction of N released from sunn hemp residues is likely not taken up by strawberry plants. Our findings highlight the challenges of using sunn hemp residues to improve N availability for meeting crop demand and enhance fruit yield in organic strawberry production while minimizing environmental N losses in Florida sandy soils.