Hydroponic Tomato Research Articles

Potato spindle tuber viroid eradicated in Western Australia.

Potato spindle tuber viroid (PSTVd) was detected for the f irst time in an isolated hydroponic greenhouse tomato (Lycopersicon esculenturn) erop in the great southern region of Western Australia (WA). An urgent eradication plan was activated because of the highly contagious nature of the pathogen. The tomato erop on the infected property was destroyed and the greenhouses and surrounding area were decontaminated. Surveys of 15 other hydroponic tomato crops did not detect any other PSTVd infected tomato plants in WA.

Abstracts, The Canadian Phytopathological Society annual meeting, London, Ontario, 2001

Abstracts, The Canadian Phytopathological Society annual meeting, London, Ontario, 2001

Using Mini-Rockwool Blocks as Growing Media for Limited-cluster Tomato Production

Rockwool is an excellent growing medium for the hydroponic production of tomato; however, the standard size rockwool blocks [4 x 4 x 2.5 inches (10 x 10 x 6.3 cm) or 3 x 3 x 2.5 inches (7.5 x 7.5 x 6.3 cm)] are expensive. The following experiments were conducted with less expensive minirock wool blocks (MRBs), on rayon polyester material (RPM) as a bench top liner, to reduce the production cost of tomatoes (Lycopersicon esculentum) grown in a limited-cluster, ebb and flood hydroponic cultivation system. Fruit yield for single-cluster plants growing in MRBs [2 x 2 x 1.6 inches (5 x 5 x 4 cm) and 1.6 x 1.6 x 1.6 inches (4 x 4 x 4 cm)] was not significantly different from plants grown in larger sized blocks (3 x 3 x 2.5 inches). When the bench top was lined with RPM, roots penetrated the RPM, and an extensive root mat developed between the RPM and the bench top. The fruit yield from plants on RPM was significantly increased compared to plants without RPM due to increases in fruit size and fruit number. RPM also significantly reduced the incidence of blossom-end rot. In a second experiment, single- and double-cluster plants were grown on RPM. Fruit yield for double-cluster plants was 40% greater than for single-cluster plants due to an increase in fruit number, although the fruit were smaller in size. As in the first experiment, fruit yield for all plants grown in MRBs was not significantly different from plants grown in the larger sized blocks. MRBs and a RPM bench liner are an effective combination in the production of limited-cluster hydroponic tomatoes.

Root mat of tomato caused by rhizogenic strains of Agrobacterium biovar 1 in the UK

Since 1993 many hydroponic cucumber (Cucumis sativus) crops in the UK have been affected by a root disorder known as root mat, a condition first described in soil and straw bed crops in the 1970s. The predominant symptom is extensive root proliferation within the rockwool propagation cube and across the rockwool slab surface. In severe cases a loss in marketable yield has been reported. Recently, the causal agent of this disease was shown to be wild-type Agrobactrium biovar 1 strains harbouring an Ri-plasmid (Weller et al. 2000). Since 1997, sporadic cases of a similar disorder have also been observed in commercial tomato (Lycopersicon esculentum) crops. Tomato plants affected by root mat were collected from crops across the UK. All crops were grown hydroponically in rockwool and the incidence of affected plants ranged from < 1% to 50%. Rhizogenic strains of Agrobacterium biovar 1 were isolated from affected but not from healthy roots, of symptomatic crops. Suspensions of three isolates of the bacterium (NCPPB 4060, 4061, 4062–National Collection of Plant Pathogenic Bacteria. Central Science Laboratory, Sand Hutton, York YO41 1LZ.) were inoculated, as in previous experiments on cucumber (Weller et al. 2000), onto six rockwool slabs each containing four young plants of one of two tomato varieties (cv. Pronto – a round variety; cv. Favorita – a cherry variety). Symptoms were initially seen five weeks after inoculation and at three months 16 plants from five of the six slabs were symptomatic. Symptoms were observed as increased root production across the propagation cube surface and swelling of the cube and/or root proliferation across the slab surface. Although root growth was excessive compared with normal tomato plants, it was less than that seen in root mat affected cucumbers. Rhizogenic Agrobacterium bv. 1 strains were re-isolated from four of the five slabs with symptoms and from the one slab without symptoms. No symptoms developed and no rhizogenic Agrobacterium strains were isolated from uninoculated control plants. Investigations on a heavily infected cherry tomato crop (cv. Favorita) at a commercial nursery indicated that fruit diameter was reduced by 2–3 mm in infected compared with healthy crops, leading to a higher proportion of unmarketable fruit (< 28 mm). Fruit numbers did not appear to be affected, although overall fruit yield was reduced by 15%. This is the first UK record of rhizogenic Agrobacterium causing root mat symptoms in tomato. Although tomato is susceptible to crown gall producing Agrobacterium strains, crown gall is a rare disease of glasshouse tomatoes. Non-pathogenic strains of Agrobacterium (without the plasmid) are commonly found on hydroponic tomato crops. This work was funded by the Horticultural Development Council (HDC) Project PC 149.

AI approaches to identification and control of total plant production systems

Recent progress in intelligent control techniques has enabled complex systems such as cultivation and fruit-storage processes to be dealt with. This paper presents the application of a hierarchical intelligent control system, which consists of an expert system and an optimizer based on neural networks and genetic algorithms, for optimizing a total plant production process. Environmental factors in the cultivation and storage processes are optimally controlled, based on the physiological status of the plant (or fruit). The expert system determines suitable environmental setpoints throughout growth, and the optimizer determines optimal environmental setpoints during important growth stages and during storage, based on plant responses. In the optimizer, neural networks were used for the identification of plant responses to environmental factors, and genetic algorithms were used to search for the optimal environmental setpoints through the simulation of the identified models. Optimal setpoints of the nutrient concentration in hydroponic tomato cultivation and optimal setpoints of the temperature during tomato storage were determined using this control technique.

Correlation of Lycopene Measured by HPLC with theL*,a*,b* Color Readings of a Hydroponic Tomato and the Relationship of Maturity with Color and Lycopene Content

Tomatoes (Lycopersicon esculentum cv. Laura) were separated, according to the ripening stage, by a sensory panel into seven groups, and color was measured on the tomato surface with a Minolta Chroma meter. The L, a, b, hue, chroma, and lycopene content were plotted against the maturity stages of the tomatoes, and several good correlations were found. The a/b ratio and the lycopene content were the parameters that allowed six of seven maturity groups in the tomato to be statistically distinguished. The lycopene content, measured by HPLC, was also correlated with the color measurements, and the a, a/b, and (a/b)(2) color factors produced the best regressions. An estimation of the lycopene content in tomatoes can be achieved by using a portable chroma meter, with a possible field usage application. Equations to calculate the lycopene content of tomatoes based on the color readings are reported.

Heat recovery in greenhouses: a practical solution

In recent years, passive infiltration of air into greenhouses has been reduced drastically. However, very low air exchange rates can lead to abnormally high levels of humidity which can damage harvests. Hence, farmers have to ventilate. In an effort aimed at reducing heating costs related to ventilation, a heat exchanger was designed to be used as a dehumidifier. A CDN$ 2000 air-to-air multi-pipe counterflow heat exchanger unit was installed in a greenhouse used for the experimental cultivation of hydroponic tomatoes and cucumbers during the winter of 1996. The first series of tests, carried out between March and May 1996 in a 576 m 3 enclosure, demonstrated that average efficiencies of η=84% and 78% were obtainable with air volumetric exchanges rates of 0.5 and 0.9 change/h, respectively. Latent heat was found to play a major role in the overall heat transfer, contributing about 40% of the total energy exchanged in some situations. The unit made of plastic is durable and rot and rust resistant. Its efficiency, mainly because of its very low level of compactness, was found to be very good in the presence of frost and ice. A commercial implementation is now considered as well as experiments in broiler houses.

Leaf Wetness Data Logger Use In Greenhouse Applications

The Leaf Wetness Data Logger (LWL) and accompanying Logbook software were designed by Spectrum Technologies Inc. as a low-maintenance tool to aid in disease prediction and spray scheduling for outdoor field-grown crops. The LWL mimics leaf surface moisture represented as a value between 0 (dry) and 15 (wet). We explored an expanded use of the LWL to large-scale commercial greenhouses for the purpose of humidity control and disease prevention. Data were collected over 15 days in a commercial hydroponic tomato production greenhouse and repeated. Results indicated that leaf wetness, as determined by the LWL, increased during irrigation periods, with cumulative effects dependent on daily irrigation requirements and climate. Irrigation was controlled by the climate control computer in response to cumulative radiation intensity. By analyzing leaf wetness in correlation with climatic conditions, more adequate irrigation scheduling may be implemented, reducing the risk of disease spread and infection.

３‐インドールプロピオン酸（ＩＰＡ）による水耕栽培トマトの青枯病防除とトマト組織におけるＩＰＡの無毒化

A specific growth inhibitor of Pseudomonas solanacearum, 3-indolepropionic acid, was tested for its effect on bacterial wilt of tomato in a hydroponic culture system. The compound had no apparent adverse effect on tomato plants at concentrations below 10μg/ml and completely protected tomato plants from wilting at 5-10μg/ml in the presence of 108cfu/ml of the pathogen. The compound was found to be glucosylated in tomato plants, suggesting that it could be used as a control agent of bacterial wilt for large scale hydroponic tomato culture.

ニューラルネットによる水耕トマトの養水分消費の推定

ニューラルネットによる水耕トマトの養水分消費の推定

Hydroponic Tomato Yield Affected by Chlormequat Chloride, Seeding Time, and Transplant Maturity

Abstract The addition of chlormequat chloride to tomato (Lycopersicon esculentum Mill.) transplants decreased fruit yield, number, and size. Flowering was accelerated both by chlormequat chloride and by transplanting at a more advanced stage of development. By transplanting a more mature plant without chlormequat chloride, yield was increased over the first 3 weeks of harvest. Although it is difficult to manage a “leggy” transplant, typical of flowering hydroponic tomato transplants grown under low light levels and close spacing, increased yield was sufficient to justify this management practice. Chemical name used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride).

Salt Stress, Mechanical Stress, or Chlormequat Chloride Effects on Morphology and Growth Recovery of Hydroponic Tomato Transplants

Abstract Growth retardants have been used to control stem elongation of hydroponic tomato (Lycopersicon esculentum Mill.) transplants. However, the residual effect of chlormequat chloride on vegetative growth reduces yield. Therefore, the recovery rate of transplant growth was compared between treatments that reduce stem elongation (salt stress, thigmic stress, and chlormequat chloride) to determine which treatments had the best combination of a fast growth recovery rate and control of stem elongation. Tomato plants were grown hydroponically during treatment and recovery periods in a recirculating nutrient solution. Although all treatments except thigmic stress initially decreased shoot dry weight, 24 days after treatment (DAT) termination night-salt stress and thigmic stress produced plants with shoot dry weight comparable to controls. Day and 24-hr salt stress and chlormequat chloride-treated plants had shoot dry weights of 40% to 60% of control 24 DAT termination. Plants treated with chlormequat chloride were still growing slower than controls 24 DAT termination. Both night-salt stress and thigmic stress are suitable prospects for use in control of hydroponic tomato transplant vegetative growth. Oscillatory wind stress applied by the sweeping motion of a leaf blower or by brushing plants with a foam rubber mat are potential commercially feasible ways to apply mechanical stress. Chemical names used: 2-chloro-N,N,N-trimethyIethanaminum chloride (chlormequat chloride).

Tropical production of tilapia ( Sarotherodon aurea) and tomatoes ( Lycopersicon esculentum) in a small-scale recirculating water system

An integrated fish and hydroponic tomato production system was evaluated for use in the US Virgin Islands. The system was constructed from readily available materials, and designed to minimize capital costs, energy and water use, and the technological skill needed for operation. Tilapia ( Sarotherodon aurea) and tomatoes ( Lycopersicon esculentum) were cultured outdoors for 181 days in a closed system containing 7.34 m 3 of water. Water quality suitable for fish production was maintained by aeration, biological filtration, sedimentation, hydroponic vegetable production and the addition of make-up water. Fish metabolites, wasted feed, and small quantities of inorganic fertilizers served as nutrient sources for tomato production. Fish survival (97.5%) and growth (2.54 g per day) were excellent with 63.6 kg of fish averaging 521 g each recovered at harvest. The total yield of ripe tomato fruit was 87.0 kg, of which 87.4% was marketable. The yield and quality of fruit produced hydroponically exceeded that produced under field trial conditions. Capital costs for the complete system were estimated to be US$612 (1979). Electrical energy and water use were 9.12 kWh day −1 and 2.6% of the total volume per day, respectively. Cost and return projections indicate the system could be operated on a profitable basis in the US Virgin Islands.

Absorption, balance and metabolism of 14C-2, 4, 6-trichlorophenol in hydroponic tomato plants

Most of the 2, 4, 6-TCP applied in the nutrient solution of the hydroculture test was volatilised; a proportion was absorbed by the developed plant roots and to a small extent isomerised. Significant portions of the non-extractable tomato plant residues were found in the isolated lignin and cellulose fractions.