Tomato Growth Promotion Research Articles

Pyrroloquinoline Quinone Is a Plant Growth Promotion Factor Produced by Pseudomonas fluorescens B16

Pseudomonas fluorescens B16 is a plant growth-promoting rhizobacterium. To determine the factors involved in plant growth promotion by this organism, we mutagenized wild-type strain B16 using OmegaKm elements and isolated one mutant, K818, which is defective in plant growth promotion, in a rockwool culture system. A cosmid clone, pOK40, which complements the mutant K818, was isolated from a genomic library of the parent strain. Tn3-gusA mutagenesis of pOK40 revealed that the genes responsible for plant growth promotion reside in a 13.3-kb BamHI fragment. Analysis of the DNA sequence of the fragment identified 11 putative open reading frames, consisting of seven known and four previously unidentified pyrroloquinoline quinone (PQQ) biosynthetic genes. All of the pqq genes showed expression only in nutrient-limiting conditions in a PqqH-dependent manner. Electrospray ionization-mass spectrometry analysis of culture filtrates confirmed that wild-type B16 produces PQQ, whereas mutants defective in plant growth promotion do not. Application of wild-type B16 on tomato (Solanum lycopersicum) plants cultivated in a hydroponic culture system significantly increased the height, flower number, fruit number, and total fruit weight, whereas none of the strains that did not produce PQQ promoted tomato growth. Furthermore, 5 to 1,000 nm of synthetic PQQ conferred a significant increase in the fresh weight of cucumber (Cucumis sativus) seedlings, confirming that PQQ is a plant growth promotion factor. Treatment of cucumber leaf discs with PQQ and wild-type B16 resulted in the scavenging of reactive oxygen species and hydrogen peroxide, suggesting that PQQ acts as an antioxidant in plants.

Root‐Knot Nematode Resistant Cowpea Cover Crops in Tomato Production Systems

Root‐knot nematodes, Meloidogyne spp., are serious pests of many crops worldwide. Recent limitations on the use of nematicides have enhanced the need to develop alternative management strategies, including host plant resistance. This study was conducted to determine the effectiveness of nematode‐resistant cowpea [Vigna unguiculata (L.) Walp.] genotypes used as cover crops for suppressing populations of M. incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood and protecting susceptible tomato (Lycopersicon esculentum Mill.) grown in rotation. In six field experiments, susceptible and resistant cowpea was grown to flowering stage and the dried tops incorporated or not incorporated into the soil. These treatments were compared to wet and dry fallowing and were conducted on nematode‐infested and noninfested plots. The experiments were conducted in the Coachella and San Joaquin Valleys, California. Resistance conferred by genes Rk and Rk2 reduced loss of cowpea biomass and M. incognita soil populations and partially suppressed M. javanica compared with susceptible cowpea, but not as effectively as fallow treatments. Incorporation of cowpea tops into the soil promoted tomato growth irrespective of nematode presence. On infested plots, tomato fruit yield was higher following growth and incorporation of resistant cowpea compared with growth and incorporation of susceptible cowpea or nonincorporation of cowpea and fallow treatments. We conclude that root‐knot nematode‐resistant cowpea is an effective cover crop for protecting susceptible vegetable crops grown under irrigation, and its beneficial effects are enhanced by incorporation of its green biomass.

Fresh-market Tomato Gas Exchange, Biomass, and Fruit Yield are Similar with Legume Cover Crops or Synthetic Nitrogen Fertilizer

Conventional production of tomatoes (Lycopersicon esculentum Mill.) requires substantial investments, intensive management and high inputs of nitrogen. High N rates invariably leave residual soil NO3-N with the potential of polluting ground water and posing health hazard to humans and animals. The objective of this study was to examine the value of cover crops as a substitute to synthetic N fertilizer in growing of tomatoes. The experimental treatments consisted of control (no N fertilizer or cover crop), Abruzzi rye (Secale cereale L), hairy vetch (Vicia villosa Roth), or crimson clover (Trifolium incarnatum L.) cover crop, and fertilization of N at 90 or 180 kg·ha-1. The treatments were replicated four times over 2 years in a randomized complete block experiment for growing `Mountain Pride' tomato on a Greenville fine sandy loam soil. The parameters used to evaluate the performance of tomato consisted of leaf area index (LAI), gas exchange (GE), above ground plant dry weight, number of fruits, dry weight of fruits, and marketable fruit yield. Tomato LAI was similar under legumes and N fertilizers. Hairy vetch and applied N at 90 kg·ha-1 influenced net photosynthesis (Pn) and transpiration (E) the most in both years at all stages of growth. Highest number of tomatoes were produced in hairy vetch and applied N at 90 kg·ha-1 plots. There was no significant difference in the above ground plant dry weight, fruit yield and dry weight of fruits between legumes and N fertilizers. The results suggested that the legume cover crops compared favorably to N fertilizers in promoting tomato growth and development and may have potential of substituting N fertilizers in fresh-market tomato production.

Rhizobacteria-Mediated Growth Promotion of Tomato Leads to Protection AgainstCucumber mosaic virus

ABSTRACT We evaluated combinations of two strains of plant growth-promoting rhizobacteria (PGPR) formulated with the carrier chitosan for the ability to induce growth promotion of tomato plants and resistance to infection by Cucumber mosaic virus (CMV). Each PGPR combination included GB03 (Bacillus subtilis) and one of the following PGPR strains: SE34 (B. pumilus), IN937a (B. amyloliquefaciens), IN937b (B. subtilis), INR7 (B. pumilus), or T4 (B. pumilus). The PGPR combinations formulated with chitosan are referred to as biopreparations. Tomato plants treated with each of the biopreparations appeared phenotypically and developmentally similar to nonbacterized control plants that were 10 days older (referred to as the older control). When plants were challenged with CMV, all plants in the biopreparation treatments and the older control treatment had significantly greater height, fresh weight, and flower and fruit numbers than that of plants in the CMV-inoculated same age control treatment. CMV disease severity ratings were significantly lower for biopreparation-treated and older control tomato plants than for that of same age control plants at 14 and 28 days postinoculation (dpi). CMV accumulation in young noninoculated leaves was significantly less for all biopreparation-treated plants and those in the older control than for the same age control plants at 14 dpi and for four of the five biopreparation treatments at 28 dpi. In those tomato plants shown to be infected, the amount of CMV in noninoculated leaves was significantly lower for three of the biopreparation treatments and the older control treatment at 14 dpi and biopreparation G/INR7 treatment at 28 dpi when compared with the control treatment. These data show that treatment of tomato plants with biopreparations results in significant enhancement of growth and protection against infection by CMV.

Enhancing resistance of tomato and hot pepper to Pythium diseases by seed treatment with fluorescent pseudomonads

Twenty isolates of fluorescent pseudomonads were evaluated for their ability to control damping-off in tomato (Lycopersicon esculentum) and hot pepper (Capsicum annuum). These isolates were characterized as Pseudomonas fluorescens and Pseudomonas putida. Two isolates, PFATR and KKM 1 belonged to P. putida and the remaining 18 isolates belonged to P. fluorescens. Among these isolates, P. fluorescens isolate Pf1 showed the maximum inhibition of mycelial growth of Pythium aphanidermatum and increased plant growth promotion in tomato and hot pepper. P. fluorescens isolate Pf1 was effective in reducing the damping-off incidence in tomato and hot pepper in greenhouse and field conditions. Isolate Pf1 was further tested for its ability to induce production of defense-related enzymes and chemicals in plants. Earlier and increased activities of phenylalanine ammonia lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) were observed in P. fluorescens Pf1 pretreated tomato and hot pepper plants challenged with Pythium aphanidermatum. Moreover, higher accumulation of phenolics was noticed in plants pretreated with P. fluorescens isolate Pf1 challenged with Pythium aphanidermatum. Thus, the present study shows that in addition to direct antagonism and plant growth-promotion, induction of defense-related enzymes involved in the phenyl propanoid pathway collectively contributed to enhance resistance against invasion of Pythium in tomato and hot pepper.

Growth and Yield of Tomatoes in Hairy Vetch-Incorporated and -Mulched Field.

For the establishment of a tomato cropping system with hairy vetch (Vicia villosa Roth), effectiveness of incorporation and mulch (no-till) of hairy vetch and nitrogen fertilizer effect on tomato (Lycopersicon esculentum Mill.) growth and yield were examined, compared with tomatoes conventionally grown in a tilled field without hairy vetch (conventionally-tilled field), in 1997 and 1999. The NO3- concentration in the petiole sap was highest 42 days after transplanting. Though it decreased to below 1, 000ppm in tomatoes grown in conventionally-tilled field 56 days after transplanting, it remained more than 2, 000ppm in tomatoes grown in the hairy vetch-incorporated field (HV-incorporated field) and hairy vetch-mulched field (HV-mulched field). The growth index (GI) was higher in the HV-incorporated and HV-mulched fields than in the conventionally-tilled field. No difference in GI was observed among the rates of nitrogen fertilizer applied to HV-incorporated and HV-mulched fields and GI in these fields reached the recommended levels for obtaining average tomato yield at the beginning of the harvest even with no nitrogen fertilizer. The NO3- concentration in the petiole sap and GI in HV-mulched field was larger than those in HV-incorporated field in early period of tomato growth. Higher total tomato yields were shown in HV-incorporated and HV-mulched fields than conventionally-tilled field in both years, especially, HV-mulched field added 0-60kg/ha nitrogen fertilizer showed similar yield obtained in conventionally-tilled field with 120kg/ha nitrogen fertilizer. Yield-increase was recognized in early and middle harvest. Though tomato yield increased as nitrogen fertilizer added in conventionally-tilled field, there were no differences in yield among rates of nitrogen fertilizers applied in HV-incorporated and HV-mulched fields. Hairy vetch used for incorporation and dead mulch contributed to the increase in NO3- concentration in the petiole sap, and promoted tomato growth and yield, especially in HV-mulched field, compared with the conventionally-tilled field. There is a possibility to reduce the nitrogen fertilizer in the tomato cropping system with hairy vetch-incorporation and hairy vetch-mulch.

Growth promotion of tomato and radish plants by solar UV radiation reaching the Earth's surface

The effect of natural solar UV radiation on the growth of tomato and radish plants was studied using polyvinylchloride films with different UV transmissions. The growth (fresh and dry weights) of tomato plants exposed to UVA (400-320 nm) radiation (UVC-320 film, transmission above 320 nm) was greater than that of plants exposed to no UV radiation (UVC-400 film, transmission above 400 nm) or to mainly near-UV radiation (400-300 nm; including UVA (400-320 nm) and the longer wavelength region within the UVB (320-280 nm); UVC-290 film, transmission above 290 nm). Furthermore, the growth promotion of tomato and radish plants on exposure to UVA has associated with an increase in chlorophyll content and photosynthetic activity. Dark respiration of tomato and radish plants was also promoted by radiation (near-UV and UVA region) through UVC-290 and UVC-320 films. Radiation with UVA delayed the senescence of tomato leaves.

Abundance, Growth and Feeding of Natterjack Toads (Bufo calamita) In a 4-Year-Old Artificial Habitat

A field experiment was conducted to investigate the effects of irrigation with treated wastewater on the nutrient distribution in cucumber and tomato plants and their fruit quality. Irrigation with treated wastewater promoted tomato growth significantly, but had definite inhibition effect on cucumber growth. After the irrigation with treated wastewater, the nitrogen in plants had the characteristics of upward translocation, potassium was easily to be accumulated in cucumber leaf but not accumulated in tomato root, and sodium was mostly accumulated in root but less enriched in leaf, not giving damage to the plants. No significant effects were observed on the distribution of calcium, magnesium, and chlorine in plants. Under the irrigation with treated wastewater, the overall quality of cucumber and tomato fruits was less affected. The nitrate concentration in cucumber and tomato fruits was increased by 5.3% and 32.9%, respectively, but still lower than the state food safety standard of China.