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Kim E. Tripp, William K. Kroen, Mary M. Peet, and Daniel H. Willits

Eight tomato (Lycopersicon esculentum) cultivars were grown for 16 weeks in greenhouses enriched for an average of 8.1 hours daily to 1000 μl CO /liter of air or in greenhouses maintained at ambient CO. Carbon dioxide enrichment significantly decreased the mean number of greenhouse whiteflies [Trialeurodes vaporariorum (Westward), Homoptera: Aleyrodidae] as measured by counts from commercial yellow sticky traps. The number of whiteflies present was negatively correlated with both seasonal foliar C: N ratio and percent C but positively correlated with percent N in the foliage. Thus, CO enrichment apparently alters plant composition in such a way as to reduce significantly the population growth of greenhouse whiteflies.

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Philip Busey, Timothy K. Broschat, and Diane L. Johnston

Phenoxy and related herbicides used in turfgrass have the potential for volatilization and movement from treated areas. Three studies assessed potential injury to subtropical landscape plants caused by volatile turf herbicides in polyethylene enclosures. Phenoxy herbicide mixtures were emphasized. There were significant differences among the seven landscape species tested. The most sensitive species were african marigold (Tagetes erecta), joseph's coat (Alternanthera ficoidea), and tomato (Lycopersicon esculentum). Severe injury was caused by exposure to herbicides containing 2,4-D isooctyl ester and MCPA isooctyl ester. Exposure to individual active ingredients 2,4-D dimethylamine, dicamba acid, atrazine, and metsulfuron resulted in no injury to the species tested.

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William H. Tietjen, Winfred P. Cowgill Jr., Martha H. Maletta, Peter J. Nitzsche, and Stephen A. Johnston

The effect of disease forecasting systems and stake or ground culture on foliar and postharvest disease control for tomato (Lycopersicon esculentum) was evaluated during two growing seasons in northern New Jersey. Foliar disease was reduced and marketable yield increased by stake culture. Percent of postharvest losses, including loss due to anthracnose, was significantly reduced by stake culture. Effectiveness of disease control schedules, weekly or forecaster-generated, was not affected by cultural system. Disease forecasting was shown to have potential for optimizing fungicide use in tomato production by controlling foliar disease and fruit anthracnose with fewer applications than a weekly schedule.

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Olga Fedorowicz, Grzegorz Bartoszewski, Maria Kamińska, Pravda Stoeva, and Katarzyna Niemirowicz-Szczytt

This study was undertaken to remedy significant yield losses in commercial tomato (Lycopersicon esculentum Mill.) and tobacco (Nicotiana tabacum L.) production caused by tomato spotted wilt virus (TSWV). One of the possible sources of resistance can be incorporation into the host plant of a viral nucleoprotein (N) gene by Agrobacterium-mediated transformation. Twelve primary transformants of tomato and 141 of tobacco were analyzed for the expression of the N gene and for resistance to the TSWV infection. The tests have demonstrated that transgenic plants were protected against virus infection irrespective of whether or not they contained detectable levels of the translational product.

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Martin P.N. Gent and Vincent Malerba

The soil within a greenhouse was heated by blowing hot air from a forced-air heater through drainage pipes buried beneath raised beds. This warmed the soil from 50F (10C) to 68F (20C) after 1 week of heating in mid-March. Soil in unheated beds did not warm to this temperature until May. The yield of tomato (Lycopersicon esculentum Mill.) planted in heated beds was higher than in unheated beds by 16% over the season in 1992, and by 14% as of early July 1993. The weight fraction of highest-quality fruit also were 11% greater in 1993. This simple method of soil heating involved negligible additional expense

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Wade J. Sperry, Jeanine M. Davis, and Douglas C. Sanders

Two crack-resistant and two crack-susceptible fresh-market tomato (Lycopersicon esculentum Mill.) cultivars were evaluated at varied soil moisture levels for physiological fruit defects and yield. Cultural practices recommended for staked-tomato production in North Carolina with raised beds, black polyethylene mulch, and drip irrigation were used. Soil moisture levels of less than −15.0, −30 to −40, and greater than −70 kPa were maintained and monitored using daily tensiometer readings. Soil moisture level had no effect on fruit cracking, blossom-end rot, zippers, or yield. However, there-were large differences among cultivars for fruit defects and total and marketable yields.

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V. Kagan-Zur, D. Yaron-Miron, and Y. Mizrahi

A spontaneous tomato (Lycopersicon esculentum Mill.) triploid was studied with a view to its commercialization. Fruits induced by auxin contained 50% more DNA and 30% more protein than their diploid counterpart. The fruits were 50% larger than those of the diploid counterpart and were juicy but seedless. All fruit quality characteristics checked (polygalacturonase activity, reducing sugars content, electrical conductivity, pH, titratable acidity, pigment content, and shelf life) were comparable to the diploid except for ethylene evolution rate, which was lower than that of the diploid counterpart, and flavor, which was superior. The line seems suitable for agricultural cultivation.

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Bernard A. L. Nicoulaud and Arnold J. Bloom

Concentrations of up to 1.0 μm NiCl2 in a nutrient solution improved growth of tomato (Lycopersicon esculentum Mill. `T-5') seedlings that received foliar urea as their sole nitrogen source. Nickel in the nutrient solution decreased the amount of urea present in the shoots and increased the amount in the roots, although it had no significant effect upon leaf urease activity. These results indicate that a) the presence of nickel in the nutrient solution improves growth of plants receiving foliar urea and b) the effect of nickel was related more to increased urea translocation from shoot to root than to enhanced leaf urease activity.

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A. Liptay and S. Nicholls

Tomato transplant (Lycopersicon esculentum Mill.) root growth in the field was directly related to N level supplied to the transplants as seedlings in the greenhouse. Root growth in the field increased exponentially when N was applied at 50 to 350 mg·liter-1. Transplant growth in multicelled trays increased in a sigmoidal fashion with N, up to 200 mg-liter'. The optimal N range for maximum survival, growth, and early yield in the field was from 100 to 200 mg-liter'. Strength of the seedling stem increased with N level curvilinearly. Seedling survival in the field was highly correlated with seedling stem strength.

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K.E. Tripp, M.M. Peet, D.H. Willits, and D.M. Pharr

Two cultivars of greenhouse tomato (Lycopersicon esculentum Mill.) were grown with ambient or 1000 μl CO2/liter during Jan.-June 1987 and 1988. In both years, CO2-enrichment increased foliar deformation and foliar starch, but during the season, foliar starch levels decreased while deformation increased. `Laura' had more deformation, while `Michigan-Ohio' had higher foliar starch concentration. During an entire season, there was no significant relationship between foliar starch concentration and deformation severity. Foliar C exchange rates in the lower canopy were not affected by severity of deformation. Data from these experiments do not support the hypothesis that excess foliar starch is responsible for foliar deformation at elevated CO2.