Tomato early blight in central Poland was caused by Alternaria solani (A. porri f. sp., solani) and A. alernata (A. tenuis). A. alternata was isolated more often than A. solani. All isolates of A. solani in controlled conditions killed tomato seedlings, while pathogenic isolates of A. alternata caused only slight seedling blight. In greenhouse tests A. solani proved to be strongly pathogenic for leaves and stems of tomato but A. alternata was weakly pathogenic. The latter species attacked only injured fruits while, A. solanicould penetrate through undamaged peel of fruits. Both of these species caused the same type of symptoms; the differences consisted only in intensification of disease symptoms. During 1974 and 1975 field tomatoes were moderately attacked by early blight. Thebest development of this disease occurred by the turn of August and September. Determinate variety 'New Yorker' was distinguished by more severe infection of stem parts of tomato whereas the fruits of a stock variety 'Apollo' were more strongly attacked.

Tomato bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (CMM) is a highly destructive disease that has caused major economic losses in tomato production worldwide. In seeking disease management alternatives, the inhibitory activity of alkaloids extracted from the Red Imported Fire Ant was studied in the laboratory and the greenhouse. Piperidine and piperideine alkaloids each significantly inhibited CMM growth on nutrient agar plates. The inhibitory activity of piperidine alkaloids was stable at 4°C and 22°C for 12 weeks and at 54°C for 4 weeks. The growth of CMM was negatively correlated with the concentration of piperidine alkaloids in nutrient broth. In the greenhouse, piperidine alkaloids also significantly reduced the symptom development on two tomato cultivars, Better Boy and DRK7018F1. This is the first demonstration that piperidine and piperideine alkaloids from the Red Imported Fire Ant are highly inhibitory against a plant-pathogenic bacterium, viz. CMM. Piperidine alkaloids could provide satisfactory management of CMM bacterial canker on tomato seedlings in the greenhouse. Our findings may lead to the development of a new group of bactericides.

The tomato leafminer Tuta absoluta is a serious worldwide threat to tomato production and its control in open-field tomato has relied heavily on synthetic insecticides, which however are not allowed in organic tomato cultivation. Furthermore, insecticide resistance to synthetic insecticides is already a major concern in populations of the tomato leafminer. Azadirachtin is one of the main biorational pesticides in use today, particularly in organic farming, and has potential as an alternative to conventional insecticides for such use. However, the effects of neem-based products of high azadirachtin content on the tomato leafminer have been little studied and very little is known of their sublethal behavioral effects on this pest species. Here we assessed the insecticidal effect of a commercial neem-based formulation (as a source of azadirachtin) against two populations of the tomato leafminer and its behavioral effects on egg-laying preferences, walking by larvae and leaf-mining. Azadirachtin caused heavy mortality in insect larvae allowing only 2.5–3.5% survival at the Brazilian recommended field-concentration (i.e., 27 mg a.i./L) with negligible difference between the populations tested. Azadirachtin also caused egg-laying avoidance (under free-choice conditions, but not in no-choice conditions) and affected walking by larvae, but not leaf-mining. These results indicate the potential of azadirachtin not only as an insecticide potentially important for organic farming, but also as an egg-laying deterrent minimizing T. absoluta infestation although it may also favor escape by larvae to exposure since it sparks behavioral avoidance.

Dielectric properties of tomatoes crucially affect their heating behaviors in an electromagnetic field and are essential for developing microwave pasteurization and sterilization processes for different tomato products. The open-ended coaxial probe technique was used to determine the dielectric properties of tomatoes over a frequency range of 300–3000MHz for temperatures between 22 and 120°C. Three tomato tissues, the pericarp tissue (including the skin), the locular tissue (including the seeds) and the placental tissue were studied separately. The effects of NaCl (0.2g/100g) and CaCl2 (0.055g/100g) on the dielectric properties of tomatoes were also investigated. The dielectric loss factors were significantly different among the three tomato tissues. However, no significant differences were found in their corresponding dielectric constants. The loss factors of the three tomato tissues decreased with increasing frequency and increased with salts added. Increasing temperature increased the loss factors of the three tomato tissues at 915MHz, but initially decreased then increased their corresponding values at 2450MHz. The differences in the loss factors of the three tomato tissues were mainly caused by the difference in ionic conductivity.

Powdery mildew disease caused by Leveillula taurica is a serious fungal threat to greenhouse tomato and pepper production. In contrast to most powdery mildew species which are epiphytic, L. taurica is an endophytic fungus colonizing the mesophyll tissues of the leaf. In barley, Arabidopsis, tomato and pea, the correct functioning of specific homologues of the plant Mlo gene family has been found to be required for pathogenesis of epiphytic powdery mildew fungi. The aim of this study was to investigate the involvement of the Mlo genes in susceptibility to the endophytic fungus L. taurica. In tomato (Solanum lycopersicum), a loss-of-function mutation in the SlMlo1 gene results in resistance to powdery mildew disease caused by Oidium neolycopersici. When the tomato Slmlo1 mutant was inoculated with L. taurica in this study, it proved to be less susceptible compared to the control, S. lycopersicum cv. Moneymaker. Further, overexpression of SlMlo1 in the tomato Slmlo1 mutant enhanced susceptibility to L. taurica. In pepper, the CaMlo2 gene was isolated by applying a homology-based cloning approach. Compared to the previously identified CaMlo1 gene, the CaMlo2 gene is more similar to SlMlo1 as shown by phylogenetic analysis, and the expression of CaMlo2 is up-regulated at an earlier time point upon L. taurica infection. However, results of virus-induced gene silencing suggest that both CaMlo1 and CaMlo2 may be involved in the susceptibility of pepper to L. taurica. The fact that overexpression of CaMlo2 restored the susceptibility of the tomato Slmlo1 mutant to O. neolycopersici and increased its susceptibility to L. taurica confirmed the role of CaMlo2 acting as a susceptibility factor to different powdery mildews, though the role of CaMlo1 as a co-factor for susceptibility cannot be excluded.

Clonostachys rosea (C.rosea) is known to induce resistance against a number of plant diseases; it is an antagonistic microorganism to Botrytis cinerea (B.cinerea). The effects of C.rosea on the control of gray mold disease caused by B.cinerea in tomato leaves were examined in this study. To examine the reactions of C.rosea in inducing resistance in tomato plants, three treatments, including B.cinerea treatment (treatment B), C.rosea treatment (treatment C), C.rosea and B.cinerea treatment (treatment C+B) and water (control), to be applied on tomato leaves were set up. The results indicated that the C.rosea treatment stimulated the activity of the superoxide dismutase (SOD), the nitric oxide (NO) and hydrogen peroxide (H2O2), while the treatment (C+B) reduced the incidence and severity of gray mold. These results indicate that C.rosea treatment has the potential to control gray mold of tomato plants and it can induce the activities of SOD, NO and H2O2 in tomato leaves infected with B.cinerea. | Liana Dalcantara Ongouya Mouekouba, Zhen-Zhu Zhang, Erinle Kehinde Olajide, Ai-Jie Wang, and Ao-Xue Wang

Bacterial wilt caused by Ralstonia solanacearum is a serious threat for agricultural production in China. Eight soil bacterial isolates with activity against R. solanacearum TM15 (biovar 3) were tested in this study for their in vitro activity towards ten genetically diverse R. solanacearum isolates from China. The results indicated that each antagonist showed remarkable differences in its ability to in vitro antagonize the ten different R. solanacearum strains. Strain XY21 (based on 16S rRNA gene sequencing affiliated to Serratia) was selected for further studies based on its in vitro antagonistic activity and its excellent rhizocompetence on tomato plants. Under greenhouse conditions XY21 mediated biocontrol of tomato wilt caused by seven different R. solanacearum strains ranged from 19 to 70 %. The establishment of XY21 and its effects on the bacterial community in the tomato rhizosphere were monitored by denaturing gradient gel electrophoresis of 16S rRNA gene fragments PCR-amplified from total community DNA. A positive correlation of the in vitro antagonistic activities of XY21 and the actual biocontrol efficacies towards seven genetically different R. solanacearum strains was found and further confirmed by the efficacy of XY21 in controlling bacterial wilt under field conditions.

Low-energy ion beam bio-technology has been applied in the biological field and has gained remarkable success in crop and microbe breeding. However, to understand how low-energy ion beams interact with biological materials remains a challenge for researchers who work for the development of ion-beam bio-technology. In this work, tomato pericarp was used as the target sample to study the effect of ion beams on the permeability of biological objects. A series of experiments were conducted via irradiating tomato pericarp samples with low-energy (10 keV ∼ 25 keV) ion beams followed by measuring the pericarp’s permeability using transmissive α particles. The transmissive spectra of α particles and the measurement of the tip number in CR39 gave a quantitative evaluation of the sputtering effect caused by low-energy ions. Meanwhile, natural red dye was used to examine the permeability of irradiated tomato pericarp samples. It was found that the sputtering effect is not only proportional to the ion energy and dose, but dependent on the ion type as well. The damage caused by Ar ions due to sputtering was much more severe than that caused by N ions sputtering with the same dose. Therefore, this study not only demonstrates the permeability difference of biological membranes before and after ion irradiation, but also provides the information on how to optimize the experimental conditions for application of the low-energy ion beam in biology.

Low-energy ion beam bio-technology has been applied in the biological field and has gained remarkable success in crop and microbe breeding. However, to understand how low-energy ion beams interact with biological materials remains a challenge for researchers who work for the development of ion-beam bio-technology. In this work, tomato pericarp was used as the target sample to study the effect of ion beams on the permeability of biological objects. A series of experiments were conducted via irradiating tomato pericarp samples with low-energy (10 keV ∼ 25 keV) ion beams followed by measuring the pericarps permeability using transmissive α particles. The transmissive spectra of α particles and the measurement of the tip number in CR39 gave a quantitative evaluation of the sputtering effect caused by low-energy ions. Meanwhile, natural red dye was used to examine the permeability of irradiated tomato pericarp samples. It was found that the sputtering effect is not only proportional to the ion energy and dose, but dependent on the ion type as well. The damage caused by Ar ions due to sputtering was much more severe than that caused by N ions sputtering with the same dose. Therefore, this study not only demonstrates the permeability difference of biological membranes before and after ion irradiation, but also provides the information on how to optimize the experimental conditions for application of the low-energy ion beam in biology.

A field experiment was conducted to investigate the effect of seed presoaking of shikimic acid (30, 60 and 120ppm) on growth parameters, fruit productivity and quality, transpiration rate, photosynthetic pigments and some mineral nutrition contents of tomato plants. Shikimic acid at all concentrations significantly increased fresh and dry weights, fruit number, average fresh and dry fruit yield, vitamin C, lycopene, carotenoid contents, total acidity and fruit total soluble sugars of tomato plants when compared to control plants. Seed pretreatment with shikimic acid at various doses induces a significant increase in total leaf conductivity, transpiration rate and photosynthetic pigments (Chl. a, chl. b and carotenoids) of tomato plants. Furthermore, shikimic acid at various doses applied significantly increased the concentration of nitrogen, phosphorus and potassium in tomato leaves as compared to control non-treated tomato plants. Among all doses of shikimic acid treatment, it was found that 60ppm treatment caused a marked increase in growth, fruit productivity and quality and most studied parameters of tomato plants when compared to other treatments. On the other hand, no significant differences were observed in total photosynthetic pigments, concentrations of nitrogen and potassium in leaves of tomato plants treated with 30ppm of shikimic acid and control plants. According to these results, it could be suggested that shikimic acid used for seed soaking could be used for increasing growth, fruit productivity and quality of tomato plants growing under field conditions.