Tomato Transplants Research Articles

Effects of Seaweed Extract Application Rate and Method on Post-production Life of Petunia and Tomato Transplants

Seaweed extracts are widely used as plant growth regulators in agriculture and horticulture for improvement of plant growth and development. This study investigated the effects of rockweed (Ascophyllum nodosum) extract application method (foliar spray or substrate drench) and rate on growth and postharvest drought tolerance of petunia (Petunia hybrida) and tomato (Solanum lycopersicum) transplants grown in a commercial peat/perlite substrate. Foliar sprays significantly affected growth of petunia and tomato, but did not improve drought tolerance of petunia and tomato. Whereas, substrate drenches significantly improved drought tolerance of petunia and tomato compared with the control. Shoot fresh weight (FW), shoot dry weight (DW), root index (RI), and chlorophyll index (SPAD) of petunia and tomato increased significantly with increasing concentration of foliar spray rate up to 5 mL·L−1, but did not change significantly with further higher foliar spray rates. Weekly substrate drenches at 20 mL·L−1 significantly decreased FW, DW, RI, and SPAD values of petunia and tomato. In this study, substrate drench at 5–10 mL·L−1 significantly increased flower number of petunia and tomato. The results of this study suggested that substrate drenches at 5–10 mL·L−1 are appropriate for the improvement of postharvest life of petunia and tomato transplants, and that foliar applications can increase plant growth.

Mechanism of antagonism by Streptomyces griseocarneus (strain Di944) against fungal pathogens of greenhouse-grown tomato transplants

Antagonism by Streptomyces griseocarneus Benedict (strain Di944), a filamentous bacterium isolated from the rhizosphere of a field tomato plant, was investigated in culture and in the rhizospheres of tomato to understand the mechanisms of suppression of damping-off and root rot of tomato plug transplants. The bacterium inhibited Rhizoctonia solani Kühn, the oomycete pathogens Pythium and Phytophthora spp., and fungal pathogens including Alternaria alternata, Botrytis cinerea, Fusarium oxysporum f. sp. lycopersici, F. oxysporum f. sp. radicis-lycopersici, F. solani, Thielaviopsis basicola and Verticillium dahlia, but not bacterial pathogens of tomato as determined by agar diffusion bioassay. Standard physicochemical analyses of the metabolites extracted from cell-free culture filtrates of S. griseocarneus Di944 identified the presence of an antifungal compound, a pentaene macrolide complex, designated as rhizostreptin. This antifungal compound was also detected by ultra-violet spectrophotometry and high performance liquid chromatography in the extract from the rhizospheres of tomato transplants grown from seeds treated with S. griseocarneus Di944 and, thus, found to be suppressive to damping-off caused by R. solani. Germination of spores and growth of mycelia of pathogenic fungi of tomato were inhibited by rhizostreptin at concentrations between 0.5 and 2 µg mL−1. Rhizostreptin was found to be more fungitoxic than other known polyene macrolides, amphotericin-B, nystatin, filipin and candicidin-type heptaene, as determined by agar diffusion bioassay. A substantial growth of S. griseocarneus Di944 in mineral medium supplemented with cell-wall components of R. solani indicated the ability of the bacterium to utilize fungal cell-wall components as carbon and nitrogen sources. This was further confirmed by the production of hydrolytic enzymes chitinase, glucanase, phospholipase and proteinase, by S. griseocarneus Di944 grown in mineral medium supplemented with glucose and (NH4)2SO4 or cell-wall components of R. solani as carbon and nitrogen sources. Secretion of extracellular antifungal pentaene macrolide and fungal cell-wall degrading enzymes is believed to be the major mechanism by which the necrotrophic mycoparasite S. griseocarneus Di944 inhibits fungi and oomycetes responsible for damping-off and root rot of tomato transplants. However, studies involving mutant strains of S. griseocarneus Di944 that are incapable of producing antifungal pentaene and fungal cell-wall degrading enzymes are needed to further confirm the mechanisms of antagonism by S. griseocarneus Di944.

Fish effluents promote root growth and suppress fungal diseases in tomato transplants

Gravel, V., Dorais, M., Dey, D. and Vandenberg, G. 2015. Fish effluents promote root growth and suppress fungal diseases in tomato transplants. Can. J. Plant Sci. 95: 427-436. Aquaculture systems generate large amounts of wastes which may constitute a beneficial amendment for horticultural crop in terms of nutrients, plant growth promoter and disease suppressiveness. This study aimed to determine (1) the nutrient value of rainbow trout farming effluents coming from two feed regimes and (2) the plant growth and disease suppressiveness effects of those fish farming effluents on tomato transplants. The effluent sludge from Skretting Orient™ (SO) had a higher content of P (38 vs. 32 mg L-1), K (23 vs. 11 mg L-1), N (19 vs. to 11 mg NO3 L-1; 186 vs. 123 mg NH4 L-1), and a higher NO3:NH4 ratio (1:9 vs. 1:13) compared with the Martin Classic (MC), while MC was richer in Mg (42 vs. 24 mg L-1) and Ca (217 vs. 169 mg L-1). For the first trial, a stimulating effect of the fish effluent was observed on plant height, leaf area and root dry biomass, while only the root biomass was increased during the second trial. Fish sludge was rich in microorganisms (97 and 142 µg fluorescein h-1 mL-1 for SO and MC, respectively) and their ability to suppress Pythium ultimum Trow and Fusarium oxysporum f.sp. lycopersici (Sacc.) Snyder & Hansen was observed. Both crude fish effluents reduced in vitro mycelial growth of P. ultimum and F. oxysporum, by 100 and 32%, respectively, while MC effluents showed a higher inhibition against F. oxysporum. When fish effluents were sterilized by filtration or autoclaving, lower in vitro inhibition of P. ultimum and F. oxysporum was observed. Mixed fish effluents reduced tomato plant root colonization by P. ultimum (by up to 5.7-fold) and F. oxysporum (by up to 2.1-fold). These results showed that fish effluent can be used as soil amendments to promote plant growth and increase soil suppressiveness, which in turn can prevent soil-borne diseases.

Fish effluents promote root growth and suppress fungal diseases in tomato transplants

Gravel, V., Dorais, M., Dey, D. and Vandenberg, G. 2015. Fish effluents promote root growth and suppress fungal diseases in tomato transplants. Can. J. Plant Sci. 95: 427–436. Aquaculture systems generate large amounts of wastes which may constitute a beneficial amendment for horticultural crop in terms of nutrients, plant growth promoter and disease suppressiveness. This study aimed to determine (1) the nutrient value of rainbow trout farming effluents coming from two feed regimes and (2) the plant growth and disease suppressiveness effects of those fish farming effluents on tomato transplants. The effluent sludge from Skretting Orient™ (SO) had a higher content of P (38 vs. 32 mg L−1), K (23 vs. 11 mg L−1), N (19 vs. to 11 mg NO3 L−1; 186 vs. 123 mg NH4 L−1), and a higher NO3:NH4 ratio (1:9 vs. 1:13) compared with the Martin Classic (MC), while MC was richer in Mg (42 vs. 24 mg L−1) and Ca (217 vs. 169 mg L−1). For the first trial, a stimulating effect of the fish effluent was observed on plant height, leaf area and root dry biomass, while only the root biomass was increased during the second trial. Fish sludge was rich in microorganisms (97 and 142 µg fluorescein h−1 mL−1 for SO and MC, respectively) and their ability to suppress Pythium ultimum Trow and Fusarium oxysporum f.sp. lycopersici (Sacc.) Snyder & Hansen was observed. Both crude fish effluents reduced in vitro mycelial growth of P. ultimum and F. oxysporum, by 100 and 32%, respectively, while MC effluents showed a higher inhibition against F. oxysporum. When fish effluents were sterilized by filtration or autoclaving, lower in vitro inhibition of P. ultimum and F. oxysporum was observed. Mixed fish effluents reduced tomato plant root colonization by P. ultimum (by up to 5.7-fold) and F. oxysporum (by up to 2.1-fold). These results showed that fish effluent can be used as soil amendments to promote plant growth and increase soil suppressiveness, which in turn can prevent soil-borne diseases.

Temporal Dynamics of Powdery Mildew (Oidium neolycopersici) and its Effects on the Host Growth Dynamics of Tomato

AbstractControlled glasshouse experiments were conducted to investigate the temporal progress of powdery mildew and its effects on host dynamics of tomato, without and with one fungicide application. Healthy tomato transplants (5‐ to 6‐week old) were artificially inoculated with powdery mildew, and disease progress as well as host growth were monitored in both fungicide sprayed and unsprayed treatments and compared with non‐inoculated plants. Actual disease severity on a plant basis increased in unsprayed plants reaching maximum severity in the proportionate range of 0.53–0.83. One fungicide spray significantly reduced the maximum disease severity by two‐ to fourfolds. Despite adjustments for defoliation, declines in the proportion of disease severity between successive assessments were evident. Whereas the estimated growth rates of diseased plants were significantly lower than that of healthy plants, no significant differences were observed in the maximum leaf area formed of inoculated and non‐inoculated plants. A considerable effect of the powdery mildew epidemics was manifested through hastened shrivelling and defoliation of diseased leaves within the tomato canopy. An average of 18–29% and 40–52% of leaves had abscised from the plant canopy at the last date of assessment in sprayed and non‐sprayed plants, respectively. Accordingly, defoliation accounted for 14–33.3% and 58.3–63.1% losses in leaf area of sprayed and non‐sprayed plants, respectively. Duration of healthy leaf area and yield of inoculated plants were also significantly reduced by powdery mildew epidemics.

Incidence of Phytophthora infestans (Mont.) de Bary on potato and tomato in Maine, 2006–2010

Abstract Late blight, caused by Phytophthora infestans (Mont.) de Bary, is a devastating disease which is found worldwide. In Maine, United States (US), we recorded late blight on potato and tomato during the 2006-2009 cropping seasons. From 2006 to 2008, over 90% of the diseased samples were collected in potato fields from northern and central Aroostook County in Northern Maine, US. Then, in 2009, an unprecedented influx of inoculum on infected tomato transplants shipped to retail garden centers throughout the Northeast US significantly changed the late blight infection patterns. In 2009, 43% of diseased samples obtained were from tomato, and 57% from potato, and disease was found to occur all over the state. Moran’s index and spatial autocorrelation analysis of disease occurrence, geographical locations, host factors, and infection levels from previous years, were not statistically significant (p > 0.05). Therefore, random distributions of late blight incidences were recorded across locations and years. Nearest neighbor analysis revealed that mean spatial distances for late blight occurrence ranged from 1.51 to 71.4 km from 2006 to 2008, and 7.4 to 126.5 km in 2009. The frequency and locations of late blight outbreaks in 2009 were substantially greater than in 2006, 2007, and 2008, as affected by the influx of inoculum and movement of infected tomato seedlings as well as conducive environmental conditions. All were contributing factors for late blight occurrence in Maine. In 2010, few disease samples were collected, indicating that the influx of inoculum in 2009 did not persist to cause widespread disease in 2010. The reduction of inocula sources, fungicide protection of susceptible hosts, and the removal and destruction of infected tomato seedlings and potato cull piles or volunteer plants, can greatly reduce late blight occurrences and improve potato production. These actions should be considered as an integral part of late blight management programmes in regions where late blight commonly occurs

Responses of Tomato and Pepper Transplants to High-Temperature Conditioning

Pretransplant treatment and environmental factors after transplanting affect plant establishment and yield in vegetable crops. Six-week-old tomato (Solanum lycopersicum L., cv. M-19) and pepper (Capsicum annuum L., cv. M-71) transplants were subjected to 38°C for 20 h as heat pretreatment (HP) and recovered at 25°C for 2 h before being subjected to heat stress of 30°C for 1, 2, 3, 4, and 6 days, along with control non-heat-treated plants. The HP increased membrane integrity, lowered electrolyte leakage, and chlorophyll degradation; increased proline and carbohydrates; shortened time to first flower formation; and increased fruit set. High-temperature conditioning could be used as a hardening method for tomato and pepper transplants.

Module of Integrated Insect Pest Management on Tomato With Growers’ Participation

Tomato, Lycopersicum esculentum L. (Solanaceae), is an important vegetable crop in the Mariana Islands (Guam, Saipan, Rota and Tinian). Because tomato is heavily attacked by both the tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) and the red spider mite Tetranychus marianae McGregor, research was begun in 2011 to develop an integrated pest management program to better protect the crop from these pests. Our previous studies have indicated nominal threshold levels for T. marianae to be 8-12 mites/leaf in the dry season and 8-14 mites/leaf during the wet season, while for H. armigera the threshold was found to be 2 eggs per 10 of the plants, followed by an additional pesticide application only if 2 damaged fruit or H. armigera larvae were detected per 50 immature fruits. Other studies have found the IPM package used here of petroleum spray oil (PSO), BotaniGard, neem, and DiPel applied 15, 30, 45 and 60 days after tomato transplant to be a viable approach, significantly reducing the pest complex and giving higher tomato yield compared to both the growers’ current practice (carbaryl or malathion, 15 applications per cropping season) and control plots. The current field study was conducted at two locations in Guam (Yigo and Inarajan), USA, in 2012 and 2013 to compare this IPM package with the growers’ current practice in larger plots designed to educate the growers. The IPM package significantly lowered the pest complex and gave higher tomato yield at both the locations. Tomato growers were invited to attend an informal IPM training program on December 16, 2013 at the University of Guam, which was attended by 48 growers from four Mariana Islands. Of these growers, 41 (85%) were aware of and understood the risks associated with traditional insecticides and recognized the concept of using an IPM package in managing tomato pests before the workshop. However, all the attendees understood the concept and benefits of IPM after the workshop. Follow up with these tomato growers found that 35 (73%) later adopted the IPM program using PSO, BotaniGard, and Dipel at 15, 30, 45 and 60 DAT in the Mariana Islands.

Effect of humic acid as an additive to growing media to enhance the production of eggplant and tomato transplants

SummaryIn two experiments, conducted in 2011 and in 2012, 14 different growing media were prepared from peat moss, vermiculite, and/or perlite with or without 0.5 g l–1 humic acid (HA) to determine the optimum growing medium for eggplant (Solanum melongena L.) and tomato (Lycopersicum esculentum Mill.) transplants. None of the media tested affected the percentages of seedling emergence or survival in either crop, although the rates of emergence were affected. Higher dry weights, relative water contents, membrane stability indices, and N, P, and K uptake values were recorded for eggplant and tomato transplants in all HA-supplemented media than in the corresponding HA-free media. In terms of efficacy, the best medium among all 14 tested was 0.5 g l–1 HA + 50% (v/v) vermiculite + 50% (v/v) perlite, followed by 0.5 g HA + 65% (v/v) vermiculite + 35% (v/v) perlite, then 50% (v/v) vermiculite + 50% (v/v) perlite without HA. The first medium was significantly better for all traits measured than the standard medium currently used for tomato and eggplant transplant production in Middle Eastern countries.

Assessing Maturity of Rotary Barrel Green Waste Composts for Use as Tomato and Sweet Pepper Seedling Starter and Transplant Growth Substrates

Maturity, which significantly affects the potential use of compost as a peat alternative substrate, or substrate component, is difficult to measure, and laboratory-based testing methods are generally unattractive to farmers, due to cost and time delays. The accuracy of relatively simple, quick, and inexpensive plant-exclusive and -inclusive methods for evaluating maturity of rotary barrel composted banana leaf (BL) and lawn clipping (LC) for use as seedling starter and transplant substrates for production of tomato (Solanum lycopersicum L.) and sweet pepper (Capsicum annum L.) seedlings were investigated. Nine substrates were tested: BL or LC compost mixed at rates of 20%, 50%, 80%, and 100% (by volume) with 0% compost; that is, PRO-MIX ‘BX’/Mycorise PRO (Premier Horticulture Ltd., Dorval, Canada) alone as the control. Compost rate affected substrate electrical conductivity (EC), which, in contrast to seedling emergence, survival, and aerial growth, increased with increasing compost inclusion rate. Compost maturity test methods produced no, low, and high levels of phytotoxicity results. Neither BL nor LC compost consistently had a greater phytotoxic effect; instead, the effect seemed to be crop specific. Leaf area was more sensitive to compounds present in the compost than root growth, and EC was the most important factor inhibiting seedling emergence, survival, and root length of tomato and sweet pepper. Microorganisms indigenous to LC compost likely suppressed the positive stimulatory effects of compost extracts diluted at 1:20 v/v on sweet pepper germination and root elongation. Solvita (Woods End Research Laboratory, Inc., Mt. Vernon, Maine), a rapid (4 h) compost maturity test, in combination with a seedling growth assay may be the simplest, least costly, and most useful method to evaluate compost use potential. PRO-MIX ‘BX’/Mycorise PRO amended with BL or LC compost at 1:5 v/v is a good alternative to peat-based substrates for use as a seedling starter and transplant substrate for production of sweet pepper seedlings.

Economic Analysis of Grafted Tomato Production in Sandy Soils in Northern Florida

In addition to controlling soilborne diseases, grafting with selected rootstocks has the potential to enhance growth and yields in tomato (Solanum lycopersicum) production. However, information is rather limited regarding its economic viability in different production systems in the United States. The objective of this study was to compare the costs and returns of grafted vs. nongrafted fresh-market tomato production under common management practices in fumigated fields in northern Florida. The field trials were conducted in Live Oak, FL, during Spring 2010 and 2011. ‘Florida 47’ tomato was grafted onto two interspecific hybrid tomato rootstocks: ‘Beaufort’ and ‘Multifort’. Grafted and nongrafted ‘Florida 47’ plants were grown on fumigated raised beds with polyethylene mulch and drip irrigation using recommended commercial production practices for nutrient and pest management. The estimated costs of grafted and nongrafted transplants were $0.67 and $0.15 per plant, respectively, resulting in an additional cost of $3020.16 per acre for using grafted transplants as compared with nongrafted plants. Grafting also led to higher costs of harvesting and marketing tomato fruit as a result of yield improvement (1890 to 2166 25-lb cartons per acre for grafted plant vs. 1457 to 1526 25-lb cartons per acre for nongrafted plant). Partial budget analyses showed that using grafted transplants increased tomato production costs by $4488.03–$5189.76 per acre depending on the rootstock and growing season. However, compared with nongrafted tomato, the net farm return of grafted tomato production was increased by $253.32–$2458.24 per acre based on the tomato shipping point prices. Sensitivity analysis further demonstrated that grafting would be more profitable as the costs of grafted transplants decreased and the market tomato prices increased. These results indicated that although grafting increased the total cost of production, the increase in marketable fruit yield generated significant gross returns to offset costs associated with the use of grafted tomato transplants. Nevertheless, further research is warranted to provide more production budget and net return data about the economic feasibility of grafted tomato production based on a wide range of commercial growing conditions in Florida.

Nanotechnology in plant disease management: DNA-directed silver nanoparticles on graphene oxide as an antibacterial against Xanthomonas perforans.

Bacterial spot caused by Xanthomonas perforans is a major disease of tomatoes, leading to reduction in production by 10-50%. While copper (Cu)-based bactericides have been used for disease management, most of the X. perforans strains isolated from tomatoes in Florida and other locations worldwide are Cu-resistant. We have developed DNA-directed silver (Ag) nanoparticles (NPs) grown on graphene oxide (GO). These Ag@dsDNA@GO composites effectively decrease X. perforans cell viability in culture and on plants. At the very low concentration of 16 ppm of Ag@dsDNA@GO, composites show excellent antibacterial capability in culture with significant advantages in improved stability, enhanced antibacterial activity, and stronger adsorption properties. Application of Ag@dsDNA@GO at 100 ppm on tomato transplants in a greenhouse experiment significantly reduced the severity of bacterial spot disease compared to untreated plants, giving results similar to those of the current grower standard treatment, with no phytotoxicity.

SUSTAINABLE PLANT FACTORY: CLOSED PLANT PRODUCTION SYSTEMS WITH ARTIFICIAL LIGHT FOR HIGH RESOURCE USE EFFICIENCIES AND QUALITY PRODUCE

This paper reviews the reasons why plant factories with artificial light are recently interested in society, requirements for sustainable plant factories, the opportunities and challenges involved in the development of the technology and industry, and types of the plants suitable for plant factories with artificial light. Sustainable plant factories need to be designed and operated for producing high quality plants and transplants with minimum use of resource and minimum emissions of CO2 and environmental pollutants. For this purpose, the concept of closed has been proposed, which is a structure with minimum ventilation, covered with thermally insulated opaque walls, containing multi-tiers (or racks) with artificial light sources. Advantages of this system over the greenhouse include: 1) culture period is shortened by 40-50% with uniform growth and high quality produce, 2) annual production capacity per floor area is 100-fold, and 3) percent reductions in resource consumption are considerable. For example, percent reduction is 100% for pesticide and 95% for irrigation water. Electricity consumption for producing one tomato transplant from a seed is about 300-400 kJ and its cost in Japan is about 1 JPY (0.008 Euro or 1 US cent as of 2011), and is 25 JPY for producing one butter head lettuce from a seed. Methods of developing integrative environmental control and reducing electricity consumption are discussed based mainly on theoretical consideration. Effects of environmental factors on the growth and development are beyond the scope of this paper.

Physiological and Reproductive Responses of Tomato and Pepper Transplants to Low-Temperature Conditioning

Transplant establishment is a critical process affecting further plant growth and development, especially under adverse environmental conditions. Chilling injury is considered the main issue for tropical and subtropical crops after transplanting early the season. Pretransplant low-temperature conditioning was applied to evaluate physiological, morphological, and reproductive responses of tomato (Solanum lycopersicum L.) and pepper (Capsicum annuum L.) transplants. Five-week-old tomato, cv. M-19, and pepper, cv. M-71, seedlings were subjected to 5°C for 0, 1, 2, 3, 4, 10, and 12 days before transplanting. Preconditioning with low temperature caused increased electrolyte leakage and proline and sugar contents as the preconditioning time increased. The opposite was observed for relative water content and chlorophyll and starch contents. Number of days and node number preceding first flower formation increased with duration of treatment. A decreasing trend of flower number, fruit number, and fruit set percentage occurred in tomato and pepper plants due to increased duration of cold temperature treatment. Treatment with 5°C for up to 4 and 3 days for tomato and pepper transplants, respectively, had the least long-term adverse effects of chilling injury.

Response of Tomato and Pepper Transplants to Light Spectra Provided by Light Emitting Diodes

Growing conditions during transplant production influence seedling quality and performance, transplant establishment, and subsequent yield. The effects of spectra combinations of blue, red, and white light, generated by monochromic light-emitting diodes (LEDs), on physiological and morphological characteristics of tomato (Solanum lycopersicum L.), cv. Kingston, and pepper (Capsicum annuum L.), cv. California Wonder, seedlings were investigated. Tomato and pepper transplants treated with monochromic red, or combinations of red with blue light, produced greater stem diameter, whereas blue light alone, or in combination with red, reduced transplant height. In tomato the most lateral branches were produced on seedlings under blue light, but pepper transplants were not affected. The most leaf area in tomato and pepper transplants was obtained under monochromatic blue or red light, respectively. Proline, an important compound related to plant stress tolerance, was produced at the highest level under blue light in both plants. For tomato, red light alone or in combination with blue or white light reduced the number of leaves required before the first cluster. This occurred in pepper transplants when higher ratios of red light (up to 100%) were applied. For both plants rates of first cluster formation and first yield were higher when combinations of blue and red lights (regardless of their ratio) were used. The most vitamin C was in fruit produced on plants developed from transplants grown under blue light. Fruit total soluble solids were also higher in tomato plants developed from blue light–treated tomato seedlings. There appear to be beneficial effects due to exposure of plants during seedling development to light spectra that extends beyond transplanting. The effects of light spectra appear to be genus or species specific. The LED technology did not differ from other technologies and has merit for production of some vegetable seedlings.

Ralstonia solanacearum: A new threat to potato production in Serbia

A survey of ware potatoes (a total of 1127 samples) from localities in Serbia during two consecutive years resulted in detection and identification of R. solanacearum in 17 tuber samples. The monitoring detected the causal agent of bacterial wilt and brown rot of potato in three districts of Vojvodina province. In 2011, the infection by R. solanacearum was confirmed in 7 samples of ware potato tubers (varieties - Saturna, Pirol, Hermes, Panda) in West Backa and South Backa Districts. In 2012, the infection by R. solanacearum was confirmed in 10 potato tuber samples (Lady Claire, Desiree, Panda, Red Fantasy and Vineta varieties) from two districts: South Backa and Central Banat. Bacterial strains obtained from positive samples were identified as R. solanacearum biovar 2 using PCR/RFLP analysis, pathogenicity test on tomato transplants, and nutritional, enzymatic and biovar determination tests. To our best knowledge, these are the only findings of R. solanacearum infection in ware potatoes in Serbia. R. solanacearum was not detected in tomato or any other host plant tested in this study. Furthermore, the bacterium was not found in any of the water samples tested, including those originating from areas in which the bacterium was found in ware potato samples.

Effect of root substrates and seed cover materials on the germination and growth of organic tomato transplants

Effect of root substrates and seed cover materials on the germination and growth of organic tomato transplants

Recent Genotypes of Phytophthora infestans in the Eastern United States Reveal Clonal Populations and Reappearance of Mefenoxam Sensitivity.

Isolates of Phytophthora infestans (n = 178) were collected in 2002 to 2009 from the eastern United States, Midwestern United States, and eastern Canada. Multilocus genotypes were defined using allozyme genotyping, and DNA fingerprinting with the RG-57 probe. Several previously described and three new mulitilocus genotypes were detected. The US-8 genotype was found commonly on commercial potato crops but not on tomato. US-20 was found on tomato in North Carolina from 2002 through 2007 and in Florida in 2005. US-21 was found on tomato in North Carolina in 2005 and Florida in 2006 and 2007. US-22 was detected on tomato in 2007 in Tennessee and New York and became widespread in 2009. US-22 was found in 12 states on tomato and potato and was spread on tomato transplants. This genotype accounted for about 60% of all the isolates genotyped. The US-23 genotype was found in Maryland, Virginia, Pennsylvania, and Delaware on both tomato and potato in 2009. The US-24 genotype was found only in North Dakota in 2009. A1 and A2 mating types were found in close proximity on potato and tomato crops in Pennsylvania and Virginia; therefore, the possibility of sexual reproduction should be monitored. Whereas most individuals of US-8 and US-20 were resistant to mefenoxam, US-21 appeared to be intermediately sensitive, and isolates of US-22, US-23, and US-24 were largely sensitive to mefenoxam. On the basis of sequence analysis of the ras gene, these latter three genotypes appear to have been derived from a common ancestor. Further field and laboratory studies are underway using simple sequence repeat genotyping to monitor current changes in the population structure of P. infestans causing late blight in North America.

Vermicompost as Substrate Amendment for Tomato Transplant Production

<p>Vermicompost may be a promising substitute for peat especially in transplant production. Vermicomposting is a sustainable solution for management of organic wastes. However, due to variability of organic wastes, vermicomposts might have varying nutrient content levels. The study compared vermicomposts from different sources on growth and nutrition of tomato (<em>Solanum lycopersicum</em> L.) transplants. Chemical composition of vermicomposts differed. Common characteristics were high pH and very high electrical conductivity. All vermicomposts stimulated growth of tomato transplants, with up to a 2.2-fold increase occurring in shoot biomass. Differences in growth were attributed mainly to differences in nutrient content of the potting mixtures, but some changes in physical and biological properties of the substrate could also be responsible.</p>

Microclimate Modification Using Eco-friendly Nets for High-quality Tomato Transplant Production by Small-scale Farmers in East Africa

Unfavorable environmental conditions, pests, and viral diseases are among the major factors that contribute to poor growth and quality of tomato (Solanum lycopersicum) seedlings in tropical areas. Improving crop microclimate and excluding insects that transmit viruses may improve transplant quality and yield in production fields. This study was carried out in two seasons at the Horticulture Research and Teaching Field of Egerton University in Njoro, Kenya, to investigate the effects of agricultural nets herein called eco-friendly nets (EFNs) on germination and performance of tomato seedlings. Tomato seeds were either raised in the open or under a permanent fine mesh net (0.4-mm pore diameter). Eco-friendly net covers modified the microclimate resulting in significantly higher day temperatures and relative humidity, compared with the open treatment. Nets increased temperature and relative humidity by 14.8% and 10.4%, respectively. Starting seeds under a net advanced seedling emergence by 2 days and resulted in higher emergence percentage, thicker stem diameter, more leaves, and faster growth leading to early maturity of seedlings and readiness for transplanting. Netting improved root development by increasing root quantity and length. Stomatal conductance (gS) and estimates of chlorophyll content were higher in seedlings under net covering compared with those in the noncovered control treatment. Insect pests and diseases were also reduced under net covering. The use of the net in the production of tomato transplants presented a 36.5% reduction in the cost of seeds, through improved emergence and reduced pest damage. All other factors held constant, healthy and quality transplants obtained under a net covering also translate into better field performance; hence, increasing economic returns for commercial transplants growers, as well as for tomato farmers. Results of this study suggest that EFNs can be customized not only for their effective improvement on growth and quality of tomato transplants but also for their pest and disease management in the nursery alone or as a component of integrated pest and disease management.