In a previous study, we demonstrated the ability of the rhizobacterium Bacillus cereus AR156 (AR156) to protect tomato against bacterial wilt caused by Ralstonia solanacearum and root-knot disease caused by Meloidogyne incognita. Here, we investigate the ability of AR156 to promote plant growth and its role in the systemic protection of tomatoes cultivated in greenhouses against bacterial speck disease caused by Pseudomonas syringae pv. tomato DC3000 (DC3000). In our experiments, the AR156 population reached 10⁵–10⁶ CFU/g rhizosphere soil, and remained at that level in the rhizosphere of tomato plants for more than 2 months. In terms of its ability to promote plant growth, AR156 increased the average biomass of the tomato by 47.7%. AR156 also elicited induced systemic resistance against DC3000, significantly reduced bacterial speck disease severity 1.6-fold, and inhibited proliferation of the pathogen by approximately 15-fold. This strain triggered the accumulation of defence-related genes (PR1 and PIN2) in tomato leaves and primed the leaves for accelerated defence-related gene expression upon challenge with DC3000. That suggested simultaneous activation of the salicylic acid and the jasmonic acid dependent signalling pathways by AR156 against DC3000. In conclusion, B. cereus AR156 was found to form robust colonies in the roots of tomato and had some beneficial effects, including biological control of bacterial speck disease via ISR and promotion of plant growth.

Greenhouse and field studies were conducted to determine tolerance of tomato to halosulfuron, imazosulfuron, and trifloxysulfuron herbicides applied through drip irrigation. In greenhouse studies, PRE- and POST-applied trifloxysulfuron caused greater tomato injury (14 and 54% injury, respectively) than PRE- and POST-applied halosulfuron (5 and 26% injury, respectively) or imazosulfuron (5 and 23% injury, respectively). All herbicide treatments in the greenhouse studies caused greater injury to tomato than the nontreated. Greater tomato injury was observed in the greenhouse from herbicides applied POST than when soil applied. Tomato injury from POST-applied halosulfuron, imazosulfuron, or trifloxysulfuron followed a linear relationship, with tomato injury increasing with increasing herbicide rate. Tomato photosynthetic rate did not differ among the herbicide treatments (32.7 to 55.0 μmol m⁻² s⁻¹) and the nontreated (38.0 to 55.0 μmol m⁻² s⁻¹). At 5 to 16 days after treatment (DAT), tomato treated with imazosulfuron POST (0.26 to 0.46 cm s⁻¹) or trifloxysulfuron POST (0.27 to 0.51 cm s⁻¹) had lower stomatal conductance compared to the stomatal conductance of the nontreated tomato (0.65 to 0.76 cm s⁻¹). Chlorophyll content did not differ among treatments at 0 to 6 DAT. At 7 to 12 DAT, tomato treated with imazosulfuron POST (34.0 to 40.1 SPAD) and trifloxysulfuron POST (35.0 to 41.6 SPAD) had lower chlorophyll content compared to the nontreated (39.1 to 48.1 SPAD). In 2008 and 2009 field studies, no tomato injury was observed. Herbicide, herbicide application method, and herbicide rate had no effect on tomato height (73 to 77 cm 14 DAT, 79 to 84 cm 21 DAT) and total fruit yield (62,722 to 80,328 kg ha⁻¹).Nomenclature: Halosulfuron; imazosulfuron; trifloxysulfuron; tomato; Solanum lycopersicum L.

Tomato plants are mainly cultivated as monocrops in Brazil by intensive using of chemical products. Aiming to contribute for the reduction of the use of pesticides and enhancing biodiversity on plantation area, we conducted field experiments with tomato plants intercropped with aromatic herbs, in Sergipe state, Brazil, to evaluate the performance of tomato plants grown in monocrop and in two intercrop designs: replacement series and additive designs. The herbs used were basil (Ocimum basilicum), rue (Ruta graveolens), fennel (Foeniculum vulgare) and peppermint (Mentha piperita). Two experiments were carried out under an organic management system and they were designed in a complete randomized blocks design with four replicates. Total height, canopy area, production, yield and land equivalent ratio (LER) were determined. Herbs used different competitive strategies in interactions. Tomato plants had lower yield in intercrop with fennel than using other intercrops. A reduction was observed on tomato yield: from 20.4 t ha-1, in monocrop, to 13.1 t ha-1 in intercrop. Fennel plants had higher height and canopy area than other intercrops used and it caused shadow on tomato plants. However, it was noted that tomato plants had lower percentage of yield loss caused by tomato fruitworm (24%) in intercrop with fennel than others. The tomato relative yield was larger in intercrop with rue (13.6 t ha-1) and lower in intercrop with fennel (6.4 t ha-1). The rue plants supported a significant increase on commercial yield of tomato fruits (about 26%). The greatest losses by tomato fruitworm damage occurred in monocrop and in intercrop with peppermint. The results show the interaction between tomato and rue plants was advantageous for tomato yields. Among herbs, basil had higher yield (96.5 t ha-1) than others. LER results reveal that all intercrops studied allowed for improving use of land.

Antagonistic interactions among invertebrate predators such as intraguild predation and cannibalism have the potential to dampen top-down impacts on shared prey. Two abundant heteropteran predators, Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter co-occur in the tomato crops of the Mediterranean horticultural area where they both attack whiteflies and lepidoptera, the dominant herbivores in the crop. Experiments in the laboratory were used to assess the incidence of intraguild predation and cannibalism in these predators. The effects of these interactions on survivorship, progeny and within-plant distributions were studied, as well as the effect of the presence of M. pygmaeus on the damage caused by N. tenuis to tomato plants. When predators of different stages coexisted, only the mortality of M. pygmaeus second-third instar nymphs caused by N. tenuis adult females was observed. When predators of the same stage (second-third instar nymphs or adult females) coexisted, mortality caused by IGP and cannibalism was observed only between adult females and usually associated to the absence of additional prey. When adult females coexisted without additional prey, the progeny of both predator species were reduced, showing a relationship only with the density and not with the presence of other predator species. However, when additional prey was offered, only M. pygmaeus progeny were reduced, showing a higher capacity of N. tenuis to maintain their reproductive potential at high densities. When both predator species coexisted, N. tenuis adult females caused more damage to tomato plants, suggesting that their coexistence could affect the crop. The consequences of conspecific and heterospecific interactions of M. pygmaeus and N. tenuis are discussed for the biological control of whiteflies and other tomato pests.

Plants use different immune pathways to combat pathogens. The activation of the jasmonic acid (JA)-signaling pathway is required for resistance against necrotrophic pathogens; however, to combat biotrophic pathogens, the plants activate mainly the salicylic acid (SA)-signaling pathway. SA can antagonize JA signaling and vice versa. NPR1 (noninducible pathogenesis-related 1) is considered a master regulator of SA signaling. NPR1 interacts with TGA transcription factors, ultimately leading to the activation of SA-dependent responses. SA has been shown to promote disease development caused by the necrotrophic pathogen Botrytis cinerea through NPR1, by suppressing the expression of two JA-dependent defense genes, proteinase inhibitors I and II. We show here that the transcription factor TGA1.a contributes to disease development caused by B. cinerea in tomato by suppressing the expression of proteinase inhibitors I and II. Finally, we present evidence that the SA-signaling pathway contributes to disease development caused by another necrotrophic pathogen, Alternaria solani, in tomato. Disease development promoted by SA through NPR1 requires the TGA1.a transcription factor. These data highlight how necrotrophs manipulate the SA-signaling pathway to promote their disease in tomato.

Recently tomato leaf miner, Tuta absoluta, has become one of the most devastating pests of tomato in Egypt, and caused serious damages to tomato production in invaded areas. For this reason, the present study was undertaken to determine the efficacy of 15 insecticides representing different pesticide groups against this insect and also to study their dissipation in tomato fruits. The laboratory experimental results revealed that profenofos, cyfluthrin, lufenuron, chlorpyriphos-methyl and indoxacarb were the most toxic insecticides as compared to other chemicals. These insecticides, 1 day after application, under field conditions caused 84.1 to 73.5% reduction in infestation. With time the bio-residual activity of these compounds gradually decreased with increase in the number of infested fruits. The initial deposits of profenofos, cyfluthrin, lufenuron and chlorpyriphos-methyl ranged from 28.6 to 6.3 ppm, depending on the rate of insecticide application. The loss rate of these amounted to 91.7 to 97.57%, 15 days after treatment. In conclusion, all tested insecticides proved effective against T. absoluta and might be used to control this pest. Further, the bioresidual activity of these compounds did not exceed more than two weeks for the best cases.

Powdery mildew is one of the most important disease concerns of tomato production in different regions of the world, which is caused by different species of Erysiphales. The most important causal agents of which are Leveillula taurica and Oidium neolycopersici. In the present study tomato farms in Qazvin province were surveyed and tomato leaves with powdery mildew symptoms were collected. After morphological studies in laboratory and using reliable resources, the causal agent of tomato powdery mildew was identified as Leveillula taurica. The host range was determined by inoculation of Leveillula taurica from tomato on nine species of plants belonging to four different plant families. All cultivars of tomato, eggplant, pepper and cucumber used in this study, showed disease symptoms on their leaf surfaces. Other plant species including potato, alfalfa, sunflower, clover and sainfoin did not get infected by the pathogen. The nucleotide divergence for the rDNA internal transcribed spacers (ITS) region between tomato mildew and 21 other Leveillula taurica isolates ranged from 0.00 to 0.031 %. The sequence of ITS region of Leveillula taurica from tomato was identical to that of eight isolates from different plant species.

Efficacy of different control methods was evaluated for disease management of tomato bacterial wilt caused by Ralstonia solanacearum. All six chemical pesticides applied to the bacterial suspension showed in vitro bactericidal activities against R. solanacearum. Minimal inhibitory concentrations (MICs) of copper hydroxide (CH), copper hydroxide-oxadixyl mixture (CH+O), and copper oxychloride-dithianon mixture (CO+D) were all 200 ㎍/ml; MIC of copper oxychloride-kasugamycin (CO+K) mixture was 100 ㎍/ml; MICs of both streptomycin-validamycin (S+V) and oxine copper-polyoxine B mixture (OC+PB) were 10 ㎍/ml. Among these chemical pesticides, treatment of the detached tomato leaves with the 5 pesticides (1 mg/ml), except for OC+PB delayed early wilting symptom development caused by the bacterial inoculation (10∨6 and 10∨7 cfu/ml). Four pesticides, CH, CH+O, CO+K and S+V, showed disease protection in pot analyses. Six plant essential oils, such as cinnamon oil, citral, clove oil, eugenol, geraniol and limonene, differentially showed their antibacterial activities in vitro against R. solanacearum demonstrated by paper disc assay. Among those, cinnamon oil and clove oil exert the most effective activity for protection from the wilt disease caused by the bacterial infection (10∨6 cfu/ml). Treatment with cinnamon oil and clove oil also suppressed bacterial disease by a higher inoculum concentration (10∨7 cfu/ml). Clove oil could be used for prevention of bacterial wilt disease of tomato plants without any phytotoxicity. Thus, we suggest that copper compounds, antibiotics and essential oils have potency as a controlling agent of tomato bacterial wilt.

With the rising popularity of organic farming, due to adverse effect of chemicals, the seaweed fertilizer industry is growing rapidly worldwide. Seaweeds act as natural plant growth stimulator and enable the plants to withstand drought, disease or frost. Root diseases of tomato and sunflower caused by root rotting fungi, Fusarium spp., Rhizoctonia solani and Macrophomina phaseolina, and root knot nematode, Meloidogyne spp., are the major constraints in tomato and sunflower production. In our studies, ethanol and water extracts of several seaweeds showed significant nematicidal activity against Meloidogyne javanica. In this study, effi cacy of three seaweeds Spatoglossum variabile, Melanothamnus afaqhusainii and Halimeda tuna was compared with a fungicide Topsin-M and a nematicide carbofuran both in screen house and under field condition. Seaweed and pesticides showed more or similar suppressive effect on root pathogens of tomato and sunflower by reducing fungal root infection and nematode’s galls on roots and nematode’s penetration in roots. However, mixed application of S. variabile with carbofuran caused maximum reduction in nematode’s penetration in roots and produced greater fresh shoot weight, root length and maximum yield of tomato under field condition. Seaweeds offer a non-chemical means of disease control, which would also protect our environment from the use of hazardous chemicals.

Viroid-caused pathogenesis is a specific process dependent on viroid and host genotype(s), and may involve viroid-specific small RNAs (vsRNAs). We describe a new PSTVd variant C3, evolved through sequence adaptation to the host chamomile (Matricaria chamomilla) after biolistic inoculation with PSTVd-KF440-2, which causes extraordinary strong (‘lethal’) symptoms. The deletion of a single adenine A in the oligoA stretch of the pathogenicity (P) domain appears characteristic of PSTVd-C3. The pathogenicity and the vsRNA pool of PSTVd-C3 were compared to those of lethal variant PSTVd-AS1, from which PSTVd-C3 differs by five mutations located in the P domain. Both lethal viroid variants showed higher stability and lower variation in analyzed vsRNA pools than the mild PSTVd-QFA. PSTVd-C3 and -AS1 caused similar symptoms on chamomile, tomato, and Nicotiana benthamiana, and exhibited similar but species-specific distributions of selected vsRNAs as quantified using TaqMan probes. Both lethal PSTVd variants block biosynthesis of lignin in roots of cultured chamomile and tomato. Four ‘expression markers’ (TCP3, CIPK, VSF-1, and VPE) were selected from a tomato EST library to quantify their expression upon viroid infection; these markers were strongly downregulated in tomato leaf blades infected by PSTVd-C3- and -AS1 but not by PSTVd-QFA.