Mountain Fresh Research Articles

Response of Hydroponic Tomato Yield and Yield-correlated Morphological Characteristics to Constant or Growth Stage-based Nutrient Management Strategies

In the United States, the annual revenue attributable to tomato production is $1 billion. However, tomato production can cause negative environmental impacts, such as water pollution, often in the form of eutrophication-causing nutrient pollution. Hydroponic production can decrease excess nutrient leaching; however, optimization of nutrient management and cultivar choices could further decrease excess nutrient discharges. The objectives of this study were as follows: to evaluate and compare the responses of tomato growth characteristics, yield, and yield components to two nutrient management regimes (varying nutrient solution concentrations by growth stage and the use of a constant nutrient solution concentration from transplant to termination), and to analyze the effects of growth habits among six cultivars (Big Beef, Cherokee Purple, Heatmaster, Legend, Mountain Fresh Plus, and Tropic) on tomato yield and yield-correlated morphological characteristics. The nutrient management strategies were applied to tomato plants, and data regarding yield and related morphological characteristics were obtained. Data were analyzed using SAS PROC GLM. An analysis revealed no significant difference in the total fruit weight/plant between nutrient management regimes (P = 0.05); however, the mean fruit weight (164.26 g) and diameter (71.70 mm) were significantly greater (P < 0.0001) for plants that received the constant concentration nutrient regime. Indeterminate plants had a significantly greater (P < 0.0001) mean fruit weight (192.76 g) and mean fruit diameter (76.42 mm). Among cultivars, Big Beef had a significantly greater (P < 0.05) total fruit weight/plant (9.25 kg). Applying a constant nutrient concentration to indeterminate cultivars, particularly Big Beef and Cherokee Purple, improved the factors analyzed and could decrease negative environmental impacts while increasing profits of the producers.

Disease Progress and Detection of a California Resistance-Breaking Strain of Tomato Spotted Wilt Virus in Tomato with LAMP and CRISPR-Cas12a Assays

Use of tomato cultivars with the Sw-5 resistance gene cluster has led to the occurrence of resistance-breaking (RB) tomato spotted wilt virus (TSWV) strains globally, including California and, recently, North Carolina and Texas. We documented disease on tomato infected with either an RB strain from California (CA-RB) or a wild type (CA-WT) strain of TSWV on tomato with (cultivar Mountain Merit) or without (cultivar Mountain Fresh Plus) the Sw-5b resistance gene and detected virus incidence over time using microneedle RNA extractions and LAMP. We developed a LAMP/Cas12a assay for detection of the CA-C118Y mutation in a CA-RB strain and tested the assay with field samples. Disease in the susceptible cultivar was less severe with CA-RB than with the CA-WT strain. In contrast, the resistant cultivar had little disease when inoculated with the CA-WT strain but exhibited stunting of greater than 50% when inoculated with the CA-RB strain. In the susceptible tomatoes, the detection rates over time by LAMP reaction were higher in CA-WT than in CA-RB-inoculated plants. In resistant tomato, CA-RB remained detectable by TSWV LAMP over 14 days, whereas the WT strain was undetectable. A two-step LAMP/Cas12a assay differentiated the two strains in 1 h. Our methods were validated with samples from TSWV-infected North Carolina fields. A phylogeny of NSm gene sequences that included North Carolina field samples revealed two independent origins of the North Carolina RB isolates. The LAMP/Cas12 assay showed excellent detection of the CA-C118Y mutation. The TSWV LAMP/Cas12a assay is adaptable for in-field applications on either a smart phone platform or heat block. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Vigorous rootstocks improve yields and increase fruit sizes in grafted fresh market tomatoes

Grafting high yielding tomato cultivars (Solanum lycopersicum L.) onto vigorous rootstocks can increase marketable yields, but questions remain regarding optimal cultural and growing conditions such as pinching and plant spacing. This study addressed some of the dynamics between grafted plants and cultural practices. Two scions, ‘Tasti-Lee’ (TL) and ‘Mountain Fresh Plus’ (MFP) were grafted onto each of three rootstocks, ‘Beaufort’, ‘Arnold’, and ‘Shield’. Plants were pinched (removal of main shoot to induce both axillary shoots to grow) or non-pinched, and spaced at 56 or 61 cm. All 32 grafted treatments were compared to the grower standard: non-grafted TL and MFP spaced at 46 cm, which were non-pinched. Fruit quality traits including soluble solids content, pH, lycopene concentration, and titratable acidity were recorded for fruit harvested from tomatoes grafted onto ‘Arnold’, ‘Beaufort’, ‘Shield’ and non-grafted TL. The overall effect of grafting TL and MFP onto vigorous rootstocks ‘Arnold’, ‘Beaufort’, and ‘Fortamino’ increased marketable yields per hectare by 24-35% compared to non-grafted grower standards. The rootstock ‘Shield’ did not significantly increase yields with either scion. TL had a more positive response to grafting than MFP. ‘Arnold’, ‘Beaufort’, and ‘Fortamino’ significantly increased TL fruit size, but the fruit size results were not as significantly impacted by graft treatments for MFP. Plants spaced at 56 compared to 61 cm generated similar yields. Pinched plants significantly increased yields over non-pinched plants by 15% in 2018 but did not impact yield in 2017. No consistent difference was observed between pinched and non-pinched plants with regard to fruit size, only plants grafted with ‘Shield’ benefited significantly from being pinched. Soluble solids content, pH, total lycopene concentration, and titratable acidity differed slightly between grafted and non-grafted plants but was unlikely to positively or negatively affect overall perception of fruit quality in tomatoes. A partial budget analysis revealed that grafting with ‘Arnold’ or ‘Beaufort’ consistently increased profits in this low-disease field.

Inorganic and Organic Amendments Affect Soil Fertility, Nutrition, Photosystem II Activity, and Fruit Weight and May Enhance the Sustainability of Solanum lycopersicon L. (cv. ‘Mountain Fresh’) Crop

One of the most important issues for modern agriculture is how to decrease fertilization rates and enhance the sustainability of crops, without decreasing yields. Two inorganic (zeolite—zeo; vermiculite—ver) amendments and their mixtures with an organic soil amendment (goat manure) (i.e., zeo + ver, manure + ver, manure + zeo) were tested, and compared to the application of a controlled release fertilizer (CRF), in order to investigate if they were able to satisfy the nutritional needs of Solanum lycopersicon L. plants. For this purpose, a 112-day pot experiment was performed. After zeo and manure application, exchangeable K was increased from 16.5 times to 37.5 times. At the end of the experiment, total plant biomass was significantly higher in the CRF treatment, compared to the ver treatments (ver, ver + manure). Leaf K concentration was significantly higher in the zeo treatment (5.93% dw), compared to those determined in the CRF, ver, and ver + manure. In contrast, significantly higher foliar N was found in the CRF (4.83% dw) and zeo + ver (4.24% dw) treatments, compared to manure + ver. Finally, photosystem II (PSII) activity was significantly higher in ver, and this was ascribed to the optimum foliar Mn found in this treatment (138 mg kg−1 dw). It is expected that these data will provide a thorough insight towards decreasing chemical fertilization inputs and enhancing the sustainability of Solanum lycopersicon L. crop.

First Report of Black Dot Root Rot, Caused by Colletotrichum coccodes, on Tomato in Kentucky High Tunnels

As the most profitable vegetable crop grown in Kentucky (KY) high tunnels, tomato (Solanum lycopersicum L.) is often produced without crop rotation. In November 2016, ‘Mountain Fresh Plus’ tomato samples were received by the University of Kentucky Plant Disease Diagnostic Lab from Nelson County, KY. The high tunnel had an extended history of tomato production, and 100% of plants were affected. Common late-season symptoms of plant dieback and fruit decay were reported. Brown discoloration with dry, cracked cankers and microsclerotia were observed on primary and secondary sample roots, respectively. Symptomatic root sections (4 to 6 mm) were sterilized with 1% NaOCl and then placed on acidified potato dextrose agar (aPDA). Hyphal tips of the cultured fungus were aseptically transferred to fresh aPDA, and then mycelium was aseptically transferred to potato dextrose broth. DNA was extracted from 3-day-old broth culture (Li et al. 2008). Polymerase chain reaction (PCR) amplicons using ITS1/ITS4 (White et al. 1990) were generated, using protocols modified from Gardes and Bruns (1993) and Matsuda et al. (2005). Modifications included 35 total cycles, 30 s annealing step, and final extension for 10 min. Additional PCR products were amplified using partial actin (ACT; Prihastuti et al. 2009) and glyceraldehyde-3-phosphate dehydrogenase primers (GPDH; Berbee et al. 1999). ExoSap-IT (Affymetrix, Cleveland, OH) was used for PCR product cleanup, and then bidirectional Sanger sequence (Eurofin Genomics, Louisville, KY) was generated for each housekeeping gene. The internal transcribed spacer sequence was submitted to GenBank (MG544880) and matched 100% on identity and coverage with multiple Colletotrichum coccodes accessions, including KY364640. ACT and GPDH sequences were used in phylogenetic trees, which further supported identification as C. coccodes. The original isolate was grown on quarter-strength PDA at 23°C. Microsclerotia developed after 7 days within sparse, white mycelium. Conidia were dislodged from 4-week-old plates flooded with sterile deionized water using a sterile micropestle and then filtered through two layers of cheesecloth. Conidia were 18 to 22 μm long and 3 to 5 μm wide and were cylindrical, aseptate, and hyaline, with cylindrical conidiophores. Acervuli on tomato roots were circular with approximately 100-μm-long setae. Two-week-old ‘Sunstart’ tomatoes were used for Koch’s postulates. Eight plants were each drenched with 25 ml of 5 × 10⁵ conidia/ml (Vrisman et al. 2017). Eight plants drenched with 25 ml of sterile deionized water were noninoculated controls. After 11 weeks, root discoloration was observed, with black acervuli with setae visible on 50× magnified root surfaces; control plants were asymptomatic and lacked fungal growth. Symptomatic root cuttings were submerged in 0.6% NaOCl for 30 s and then plated on quarter-strength PDA. Mycelium was macroscopically visible after 1 week at ambient temperature. Microscopic examination indicated the fungus was morphologically indistinguishable from mycelium, conidiophores, and conidia of the original isolate, confirming Koch’s postulates. This experiment was repeated with the same results. Although C. coccodes and Pyrenochaeta lycopersici were recently reported to cause brown root rot complex in high tunnel tomato (Vrisman et al. 2017), P. lycopersici was not found here. This first report of black dot root rot in intensive high tunnel tomato production in KY reiterates the need for aggressive sanitation prior to disease development, because severe pathogen pressure in soil may necessitate relocation of the high tunnel.

Effect of Tomato Rootstock on Hybrid and Heirloom Tomato Performance in a Midwest High Tunnel Production System

High tunnels allow vegetable growers to extend the growing season, increase crop production, and improve produce quality. Tomatoes (Solanum lycopersicum L.) are the most widely grown crops in high tunnels; however, tomato production in high tunnels can be challenging. Continuous cropping in high tunnels can increase soil-borne disease pressure and can lead to soil salinity or nutrient depletion issues. Based on preliminary research, we hypothesized that use of the rootstock ‘RST-04-106-T’ would increase yield and quality of heirloom and hybrid tomato scions compared with nongrafted plants. To test this hypothesis, our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth of grafted and nongrafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and nongrafted ‘Cherokee Purple’ (heirloom) and ‘Mountain Fresh Plus’ (hybrid) tomatoes were grown in the same high tunnel for two seasons (7 May–20 Oct. 2015 and 29 April–7 Oct. 2016) at the Horticulture Research Station in Ames, IA. Grafted plants produced significantly more marketable fruit, although marketable and total fruit weight did not increase significantly. Individual fruit size was unaffected by grafting. Across cultivars, mean soluble solids content (SSC) in fruit was 0.3 °Brix lower in grafted plants as compared with the nongrafted control. Grafting did not affect lycopene content of fruit. Grafting increased stem diameter by an average of 0.8 mm, but overall plant biomass was unaffected. The effect of grafting on leaf chlorophyll concentration (SPAD readings) was mixed. In addition, grafting increased leaf chlorophyll concentration in ‘Cherokee Purple’ but decreased it in ‘Mountain Fresh Plus’ plants. Grafting is a valuable tool in tomato production, but the impact of ‘RST-04-106-T’ rootstock use appears to be specific to certain soil types with high incidence of bacterial wilt.

Accumulation of Mineral Nutrients and Phytochemicals in Lettuce and Tomato Grown in High Tunnel and Open Field

High tunnel production of horticultural food crops is becoming increasingly popular and has a significant impact on their growth, productivity and nutritional quality. The present study examines the effect of high tunnel production of lettuce (Lactuca sativa cv. “Two Star” and “New Red Fire”) and tomato (Solanum lycopersicum cv. “Celebrity” and “Mountain Fresh”) on their nutritional quality relating to major nutrients and health-promoting phytochemicals. High tunnel environment increased the concentration of N (protein) in both lettuce and tomato relative to the open field cultivation. The accumulation pattern of mineral nutrients in high tunnel was similar in green-leaf and red-leaf lettuce varieties. Lettuce varieties grown in high tunnel had higher accumulation of C, S and Zn relative to those grown in open field. However, high tunnel environment suppressed the accumulation of many micronutrients such as Mg, Fe, Cu and Mn in both lettuce varieties but not in tomato. For example, accumulation of Fe was reduced by more than 80% in “Two Star” and by more than 55% in “New Red Fire” under high tunnel. It also suppressed the levels of many health-promoting phenolic compounds such as chlorogenic acid, chicoric acid, rutin and kaempferol in green-leaf lettuce and gallic acid in red-leaf lettuce. High tunnel environment improved the soil nutrient status but reduced the radiation levels (PAR, UV-A and UV-B) received by the crops. The results show that the high tunnel production has a significant impact on the nutritional quality relating to protein and mineral nutrients in both crops and health-promoting phytochemicals in lettuce.

Nitrogen, phosphorus, calcium, and magnesium applied individually or as a slow release or controlled release fertilizer increase growth and yield and affect macronutrient and micronutrient concentration and content of field-grown tomato plants

The U.S. Environmental Protection Agency (USEPA) has restricted concentrated animal feeding operation (CAFO) release of waste products into U.S. waters. These waste products must be disposed of using best management practices. Most of the waste is spread on cropland, but some operations have found other creative uses for waste products. Use of a phosphorus (P) reduction system to remove P from wastewater results in magnesium ammonium phosphate (MAP), a slowly soluble fertilizer. Using a P reduction system will not eliminate the need for land application of manure and wastewater, but it reduces the nutrient load in the waste that is applied thereby making compliance with regulations easier. In the first year of this study, MAP was compared to a controlled release fertilizer (CRF) with a similar nutrient element ratio on plant growth, fruit yield, nitrogen (N), P, potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn) concentration in tomato (Solanum lycopersicum L. ‘Mountain Fresh Plus’) plant parts. Plant growth and fruit production were similar with the two fertilizers, but the number of tomato culls was greater with either fertilizer than on control plants. Foliar N, P, Ca, and Mg concentration did not differ regardless of fertilizer treatment. Plants fertilized with CRF had a greater leaf K concentration than those fertilized with MAP, but foliar K concentration did not differ between fertilized and nonfertilized plants. Iron and Mn concentration in above-ground vegetative plant parts (stems and leaves) did not differ regardless of fertilizer treatment, but Zn concentration increased linearly as CRF increased. In the second year, MAP, each of the essential elements contained in MAP separately, and a hand mixture of each of these elements was tested for their effect on tomato plant growth, fruit yield, and tissue N, P, K, Ca, Mg, Fe, Mn, and Zn concentration and content. Magnesium ammonium phosphate and the hand mixture of fertilizer resulted in greater above-ground biomass excluding fruit stem weight and fruit yield than any of the individual nutrient treatments. Calcium sulfate resulted in a greater number and weight of tomatoes harvested than MAP. Nitrogen concentration did not differ among the fertilizer treatments for roots, stems, or leaves, but N content was greater in red fruit with the hand mix of fertilizer than with no fertilizer or with ammonium sulfate or Mg oxide. In immature green fruit at termination of the study, N content was greater with no fertilizer or Ca sulfate than with MAP or triple superphosphate (TSP). Phosphorus, K, and Ca concentrations did not differ among fertilizer treatments for any tissue tested. Magnesium concentration in green tomatoes differed among fertilizer treatments such that Mg concentration of green tomatoes from plants fertilized with TSP was greater than Mg concentration of green tomatoes fertilized with ammonium sulfate or Mg oxide. Phosphorus and K content of green fruit differed among fertilizer treatments with P and K concentration highest in green fruit from plants fertilized with Ca sulfate and lowest in green fruit from plants fertilized with MAP or TSP. Iron and Mn concentrations did not differ among fertilizer treatments for any tissue tested. Zinc concentration in leaves was greater when plants were fertilized with MAP, TSP, Ca sulfate, or Mg oxide than with ammonium sulfate. Zinc concentration of green fruit was greater when fertilized with MAP than with the hand mix, Ca sulfate or Mg oxide. Iron content was highest in green fruit from plants fertilized with TSP and lowest in plants fertilized with ammonium sulfate or control plants. Manganese content of leaves from control plants was greater than that of plants receiving ammonium sulfate while red fruit from plants fertilized with the hand mix had a greater Mn content than red fruit from any other treatment. Foliar Zn content was greater in plants fertilized with Ca sulfate than in those fertilized with the hand mix, ammonium sulfate, or TSP. In contrast, Zn content of red fruit fertilized with the hand mix was greater than for red fruit in any other treatment. Green fruit from control plants and those receiving MAP had a greater Zn content than plants fertilized with the hand mix, TSP, or Mg oxide. Fertilizer application increased Fe, Mn, and Zn content of several plant tissues. None of the labels of fertilizers applied stated that they contained micronutrients; however, small amounts of contamination were possible. Differing micronutrient contents of various plant tissues among fertilizer treatments were probably associated with other elements affecting plant growth or nutrient uptake. The nutrient elements present in the various fertilizers were not always the nutrient elements affected in the plants likely due to another element that may have limited plant growth or nutrient uptake.

First Report of Tomato Pith Necrosis Caused by Pseudomonas mediterranea in the United States and P. corrugata in Ohio

Tomato (Solanum lycopersicum, cvs. Mountain Fresh, Big Dena, and Trust) plants with symptoms of pith necrosis were received from six commercial high tunnels in Ohio during May and July 2012. Disease incidence ranged from 1 to 5%. Symptoms included wilting of shoots, dry, dark brown coalescent lesions on stems, brown discolored pith with a ladder-like appearance, and in some cases, adventitious root formation. Bacterial streaming was observed microscopically from necrotic stem tissue. Bacteria were isolated from surface-sterilized diseased stem tissue by plating 10-fold serial dilutions onto yeast dextrose carbonate (YDC) and Pseudomonas F (PF) agar media. The majority of the colonies recovered were similar in morphology on YDC: round and mucoid, with a greenish center that later became dry and winkled with a curly margin, and producing a yellow-green diffusible pigment. Colonies were creamy, yellow-brown in color and non-florescent on PF medium. Nine isolates from six plant samples were purified. All isolates were gram-negative, levan negative, oxidase positive, and potato rot negative. Three isolates were positive and six were negative for arginine dihydrolase activity. None induced a hypersensitive reaction in tobacco. All isolates grew at 37°C. The isolates were further identified by PCR assays using species-specific primers PC5/1-PC5/2 for Pseudomonas corrugata and PC1/1-PC1/2 for P. mediterranea (1,2). DNA of a reference P. mediterranea strain from Turkey was used as a positive control. A 600-bp band was amplified using P. mediterranea primers from the six arginine dihydrolase negative isolates recovered from four of six samples. An 1,100-bp band was amplified from the three arginine dihydrolase positive isolates from two other samples using P. corrugata primers. The 600-bp PCR products amplified from the P. mediterranea reference strain and isolate SM664-12 were purified and sequenced. The DNA sequence of SM664-12 was 99% aligned with that of the reference strain from Turkey and a BLAST search in NCBI indicated only one match with P. mediterranea strain G-229-21 (Accession No. EU117098.1), with an E-value 1e-145 and 84% identity. P. mediterranea (SM664-12) and P. corrugata (SM658-12) were each inoculated onto four 4-week-old tomato plants (cv. Mountain Fresh) by injecting a 50 μl bacterial suspension (108 CFU/ml) into the stem at the axil of the first true leaf (2). Negative control plants were injected with sterile water. Plants were kept in a mist chamber for 72 h at 25°C, then moved into a growth chamber maintained at 25/20°C day/night, 12-h light/dark, and 80% relative humidity. Plants exhibited dark brown lesions at the inoculation site after 4 weeks and brown discoloration of the pith developed, whereas no lesions were observed in control plants. The reisolated bacteria were tested by PCR and identified as P. corrugata and P. mediterranea. Therefore, we have confirmed that tomato pith necrosis in Ohio involves at least two bacteria, P. corrugata and P. mediterranea. Although tomato pith necrosis has been observed in Ohio since the 1990s, to our knowledge, this is the first confirmation of a causal agent as P. corrugata in Ohio and the first report of P. mediterranea causing tomato pith necrosis in the United States.

GGE Biplot Analysis of Tomato F1 Hybrids Evaluated Across Years for Marketable Fruit Yield

Genotypes are generally evaluated in multi-environments to determine their consistent performance across locations and years. Several techniques are available to conduct such valuations. We used GGE biplot technique to understand the genotypic and genotype × year interaction in tomato (Solanum lycopersicum L.). Five F1 hybrids of tomato were evaluated from 2003 to 2008 in North Carolina for total marketable fruit yield. Significant (P < 0.05) genotype × year interaction indicated the necessity of further analysis to select the genotype that had high yield and stability across years. ‘Mountain Fresh’ was the best hybrid as far as yield and stability across years were concerned, followed by ‘Crista’; ‘Mountain Glory’ was highly unstable for marketable fruit yield. We concluded that ‘Mountain Fresh’ could be considered an ideal hybrid that can also be used as control for evaluation of other F1 hybrids. Close association between field performance and GGE biplot findings indicated that GGE biplot is a useful tool to graphically visualize the high-yielding and stable genotypes across years.

Over-expression of snakin-2 and extensin-like protein genes restricts pathogen invasiveness and enhances tolerance to Clavibacter michiganensis subsp. michiganensis in transgenic tomato (Solanum lycopersicum)

Two tomato proteins were evaluated by over-expression in transgenic tomato for their ability to confer resistance to Clavibacter michiganensis subsp. michiganensis (Cmm). Snakin-2 (SN2) is a cysteine-rich peptide with broad-spectrum antimicrobial activity in vitro while extensin-like protein (ELP) is a major cell-wall hydroxyproline-rich glycoprotein linked with plant response to pathogen attack and wounding. Tomato plants, cultivar Mountain Fresh, were transformed via Agrobacterium tumefaciens harboring a binary vector for expression of the full-length SN2 gene or ELP cDNA under the regulation of the CaMV 35S promoter. Molecular characterization of PCR-positive putative T(0) transgenic plants by Northern analysis revealed constitutive over-expression of SN2 and ELP mRNA. Junction fragment analysis by Southern blot showed that three of the four SN2 over-expressing T(0) lines had single copies of complete T-DNAs while the other line had two complete T-DNA copies. All four ELP over-expressing T(0) lines had a single copy T-DNA insertion. Semi-quantitative RT-PCR analysis of T(1) plants revealed constitutive over-expression of SN2 and ELP. Transgenic lines that accumulated high levels of SN2 or ELP mRNA showed enhanced tolerance to Cmm resulting in a significant delay in the development of wilt symptoms and a reduction in the size of canker lesions compared to non-transformed control plants. Furthermore, in transgenic lines over-expressing SN2 or ELP bacterial populations were significantly lower (100-10,000-fold) than in non-transformed control plants. These results demonstrate that SN2 and ELP over-expression limits Cmm invasiveness suggesting potential in vivo antibacterial activity and possible biotechnological application for these two defense proteins.

Alfalfa-based Organic Amendment in Peat-compost Growing Medium for Organic Tomato Transplant Production

In the last decade, organic production has been the fastest growing segment in U.S. agriculture. With increase in organic acreages there is a strong and growing demand for organically grown transplants. As a result of limited commercial availability of certified vegetable transplants, growers often produce their transplants on-farm. Commercial organic mixes for organic transplant production may not be locally available and are usually expensive. Growers often design their own mixes using compost and other organic amendments. The purpose of this study was to evaluate the incorporation of alfalfa-based amendment in a peat-compost medium for organic tomato transplant production. Growing medium of 2 peat:1 vermiculite:1 compost (by volume) was amended with 0%, 0.6%, 1.2%, 1.8%, or 2.4% weight by weight of alfalfa-based organic amendment and incubated for 0, 1, 2, 3, or 4 weeks. Medium pH and electrical conductivity (EC), seed germination (untreated Solanum Lycopersicon L. ‘Mountain Fresh’ seed), transplant dry weight, height, stem diameter, and SPAD values were measured. Medium pH increased with addition of alfalfa-based amendment but remained within the range of 5.5 to 7.0. Germination percentages were less than 50% in amended medium that was either not incubated or incubated for 4 weeks. Germination was greater than 75% if amended media were incubated for 1, 2, or 3 weeks. Seeds grown in peat-compost without any amendments had the highest germination rates; however, severe nutrient deficiency suppressed seedling growth. Relative to growth in medium with no amendments, plants growing in the amended medium had increased stem diameter, height, leaf chlorophyll content, and plant dry weight (90% to 160% more), provided the amended medium was incubated for at least 1 week. Application rate of 0.6% or 1.2% of alfalfa-based amendment produced transplants with suitable growth characteristics and met commercially acceptable standards for transplanting and handling at a reasonable estimated cost.

Field Performance of Aliphatic-aromatic Copolyester Biodegradable Mulch Films in a Fresh Market Tomato Production System

Removal and disposal of polyethylene mulch in vegetable production represents a high economic and environmental cost to society. This study was conducted in 2006 and 2007 at Michigan State University to test the field performance of new biodegradable mulches using ‘Mountain Fresh Plus’ tomato (Solanum lycopersicum) as a model crop. Treatments included two biodegradable mulches (black and white), each with two thicknesses (35 and 25 μm). A conventional low-density polyethylene (LDPE) mulch of 25 μm was included as a control (a mulch commonly used by vegetable growers). Data loggers were installed 2 cm into the soil under the various mulches to record soil temperature. The experiment used a randomized complete block design with four replications. The mulches were used on a raised bed, drip irrigation system. Mulch degradation, soil temperature, tomato growth, weed density, and biomass were assessed during the seasons. Tomatoes were harvested at maturity and were fruit graded according to market specifications. Results indicate that soil temperature under the biodegradable mulches was greater than that under the LPDE mulch during the first week. Starting the second week, soil temperature dropped gradually under all the biodegradable mulches. The drop in temperature was greatest with the white mulch. Due to premature breakdown of the white mulches, weed pressure was high, resulting in smaller plants with low yield in 2007. Tomato growth, yield, and fruit quality from the black mulch was equivalent to that in the LDPE mulch. Future studies will optimize biodegradability of the mulches and test mechanical laying of the black mulch under commercial production.

(413) Evaluating Tomato Production during the First Year of Organic Transitioning in High Tunnels

High tunnels offer growers in temperate regions the ability to extend the production season. Past research has shown that these low-input structures also reduce disease and pest pressure. These characteristics make high tunnels extremely attractive to organic growers. Tomatoes (Lycopersiconesculentum Mill.) are the crop most often produced in high tunnels in Pennsylvania and many producers are interested in combining both high tunnel and organic production methods. Growers may be hesitant to transition to organic production due to conceptions concerning reduced yields specifically during the 3-year transition period to USDA certified organic status. A field trial investigating tomato production in high tunnels during the first year of organic transitioning was conducted in 2004 at The Penn State Center for Plasticulture, Russell E. Larson Agricultural Research Center, Rock Springs, Pa. The objective of this research was to evaluate yield of the four cultivars Big Beef, Mountain Fresh, Plum Crimson, and Pink Beauty in an organic system relative to a scheduled fertilization/irrigation regime and a fertilization/irrigation regime employed using T-Systems International's Integrated Agronomic Technology. Data collected included total weight, total fruit number, weight by grade, fruit number by grade, total marketable yield, and fertilizer and water usage. Yield across cultivars ranged from 4.96 kg/plant to 6.83 kg/plant. `Pink Beauty' exhibited the lowest yields in both treatments, while `Plum Crimson' and `Mountain Fresh' exhibited the highest yields in the IAT and scheduled treatments, respectively. This experiment will be repeated in 2005 to further evaluate the performance of these cultivars.

(412) Tomato Diseases

Afield study of organic production of tomato (Lycopersiconesculentum Mill.) in high-tunnels was conducted in 2004. `Mountain Fresh' was transplanted 31 Mar.; `Ultra Sweet' and `Sun Leaper' were transplanted on 21 July. The primary objective was to determine the feasibility of obtaining two crops of fresh-market tomatoes by starting plants 4–8 weeks earlier than the average last spring-killing frost, and extending the growing season 4–6 weeks past the average first fall-killing frost. Plants were started at weekly intervals for 4 weeks in both seasons. Data and observations were recorded on the yield of marketable fruits, plant growth and development, and plant health. Other objectives were to evaluate: 1) the benefits of using a selective UV-blocking film on plant growth and development, disease events; and 2) compost amendments on soil improvement and disease control. Major cultural challenges included water management, soil texture/drainage, prevention of chilling injury, plant support, and adequate ventilation. Major disease/pest challenges involved stalk rot caused by Sclerotinia sclerotiorum in the spring, powdery mildew in spring and late summer, Alternaria and Septoria leaf blight in late summer, and aphids, tomato hornworm, corn earworm, and beet army worm also in late summer. In addition, macrofaunal intrusions by fox, mice, and birds occurred sporadically. Poor drainage and stalk rot in the spring necessitated relocating the tunnels to an uninfested site with better drainage. The fall crop yielded high numbers of marketable quality fruits, well beyond the 15 Oct. average killing frost date. The results suggest that with improved management, there is a considerable potential for profitable extended-season production of organic tomatoes in this region.

TOMATO YIELD AND SPOTTED WILT VIRUS INCIDENCE AMONG CULTIVARS IN A MISSISSIPPI TRIAL

Mississippi's two largest tomato-growing areas are in Smith and George Counties. The Truck Crops Branch Experiment Station in Crystal Springs is the closest vegetable research site to Smith County but does not share the same soil type. Tomato spotted wilt virus (TSWV) reduces fruit yield and marketability, and its incidence appears to be increasing in the state. The objectives of this trial were 1) to determine fruit yield and TSWV incidence in tomatoes (Lycopersicon esculentum) grown in central Mississippi, and 2) compare yield and relative yield among cultivars and between locations. Tomato seedlings were transplanted to the field in April 2004 in Smith and Copiah County plots. Production practices included raised beds, black plastic mulch, drip irrigation, and fertilizer applied pre-plant and as side-dressings based on soil test and regionally recommended practices. TSWV incidence was recorded in each plot in Smith Co. in June 2004. In both locations, `Amelia' and `Mountain Spring' were among the top yielding entries. In Smith, the top entries also included `BHN 543' and two commercial experimental entries. In Copiah, `Florida 47 R', `Biltmore', `Mountain Fresh', and `BHN 543' also produced high marketable yields. `Florida 47R', `Bush Celebrity', and `Mountain Fresh' were among the poorest yielding varieties in Smith County. Incidence of TSWV was not formally rated in Copiah. In Smith, percent symptomatic plants per plot were negatively correlated with yield. Symptoms were found on entries reportedly resistant or tolerant to TSWV.

ORGANIC TOMATO PRODUCTION IN OKLAHOMA

Plots were established at the Lane Agricultural Center in Lane, Okla., in 2003 for the purpose of conducting research in certified organic vegetable production. A field was selected that had been in pine timber since 1985. The field was cleared, plowed, disked, and land-planed. To establish a baseline for future reference, soil samples were collected on a 30 × 30 ft grid. Lime was added to adjust the pH. Poultry litter was added to the field as a fertilizer, and was incorporated by disking. Turnips were grown as a cover crop during the winter of 2003–04. In Spring 2004, the field was divided into four equal sections, which were planted with either tomatoes, sweet corn, watermelons, or southern peas. Tomatoes were planted using both determinate and indeterminate types. Plants were selected based on reported properties of interest to organic growers, such as disease resistance, pest resistance, or heat-set capabilities. The cultivars with greatest yield were Sunny, Solar Set, Classica, Sun Leaper, and Mountain Fresh. Visual disease ratings were taken throughout the season. Copper sulfate was used as a fungicide. The cultivars with the lowest disease ratings were Amelia, Peron, Celebrity, Florida 91, and Mountain Fresh. The major insect pest throughout the season was aphids. Aphid counts reached 6.9 aphids per leaf on 11 June. Two applications of AzaDirect, a neem extract, reduced aphid populations to 1.0 aphid per leaf on 17 June, 0.1 aphid per leaf on 25 June, and 0 aphids on 9 July.

Plant Density and Inter-row Polyethylene Mulch Treatment Affect Growth and Yield of Tomato

A field study was conducted to compare the effect of different planting densities and polyethylene mulch treatments on growth and yield of `Mountain Fresh' trellised tomato grown on raised beds on 1.8-m centers. The experiment design was a split plot with four replications and four mulch treatments as main effects: 1) standard black mulch (B), 2) Sonoco red mulch (R), 3) black mulch with interrow (between beds) reflective white on black mulch (B/W), and 4) red mulch with inter-row R/W. Subtreatments were three within-row spacings: 1) 0.60 m (8966 plants/ha); 2) 0.45 m (11955 plants/ha; standard spacing), and 3) 0.30 m (17932 plants/ha). Yield was determined from eight-plant plots and adjacent plants were harvested at regular intervals to determine plant biomass accumulation and partitioning of biomass among roots, stems, leaves, and reproductive organs. There was a linear increase in yield among mulch treatments with increasing plant density. The B/W mulch treatment increased midseason and total yields ≈20% over that of the other mulch treatments. Fruit yield of plants with the B/W mulch treatment at the 0.3-m spacing was 54% higher (151 MT/ha) than that of plants grown on black mulch with the standard plant spacing of 0.45 m (97.9 MT/ha). There was a linear decrease in fruit size with increasing plant density; however, plants grown at the 0.30-m spacing on the B/W mulched plots exhibited only a 2.7% decrease in fruit size as compared to plants grown at the standard 0.45-m spacing on black mulch.

The Kentucky Tomato, Part II

We conducted trials of vine-ripened, staked tomato cultivars in 1998 and 1999 to identify a variety suitable for marketing as a premium “Kentucky Tomato.” Essential qualities of our ideal Kentucky tomato were determined in conversations with marketing specialists at the Kentucky Dept. of Agriculture and merchandising managers from the state's largest supermarket chain. A carefully selected group of 14 varieties (including 10 from the 1998 trial) was evaluated at two locations for yields, returns per acre, appearance, and quality in 1999. New varieties were compared with commercial standards `Mountain Spring' and `Mountain Fresh'. Yields of different sizes and grades of marketable fruit were multiplied by appropriate market prices for a given harvest date and summarized in a single “income per acre” variable for each variety. Although many varieties were in the highest 1999 income group (`Fabulous', `Mountain Spring', `Emperador', `Florida 47', `Sunleaper', `Floralina', `Mountain Fresh', `SunGem', NC 98274, `Enterprise'), not all were acceptable in terms of fruit quality and firmness. `Fabulous' and `Emperador' had higher percentages of fruits with radial cracks at one location in 1999 than in 1998. Consumer taste tests were conducted in 1998 and `Mountain Fresh' and `Floralina' were considered the best tasting among the six varieties tested. `Sunleaper', `Floralina', `SunGem', NC 98274, and `Fabulous' (for local markets) together with `Mountain Fresh' were considered prime `Kentucky Tomato' candidates and were recommended for further testing in farmers' fields in 2000.

NC 109 Tomato Breeding Line: `Mountain Fresh' F1 Hybrid

NC 109 Tomato Breeding Line: `Mountain Fresh' F1 Hybrid