Tomato, worldwide, is infected by several viral diseases which cause stunting, leaf curl, yellowing, mosaic, mottling, necrosis and shoe-string symptoms on plants, leaves or fruits. Among them, bud necrosis disease caused by an orthotospovirus is emerging as a major constraint to the cultivation of tomato for resource-poor farmers. In the Indo-Gangetic eastern plains, bud necrosis disease incidence on tomato ranged from 0 to 45% under field conditions during 2015 and 2016, along with other diseases such as leaf curl and mosaic caused by begomoviruses (0–35%) and tobamoviruses (0–18%) respectively. Thirty four viral infected samples collected from 11 different villages were screened for different viruses using serological and PCR-based methods. The result revealed that most samples were positive for RNA (peanut bud necrosis virus, tomato mosaic virus) and DNA (tomato leaf curl New Delhi virus, tomato leaf curl Gujarat virus, tomato leaf curl Palampur virus, tomato leaf curl Bangalore virus, tomato leaf curl Karnataka virus) viruses along with their satellites (DNA-α and DNA-β) respectively. Further, the incidence of bud necrosis correlates to the weather parameters, which demonstrate that a long dry spell leads to higher incidence of viral disease, whereas lower incidence was observed during the rainy period considering a reduced vector population.

During the last several years, certain bacterial and viral diseases caused high losses in tomato and pepper production in Croatia. Causal agents of these diseases were Pseudomonas syringae pv. tomato, Clavibacter michiganensis ssp. michiganensis, Tomato spotted wilt virus (TSWV) and Cucumber mosaic virus (CMV). These pathogens are briefly described, with an emphasis on their way of spreading and control measures.

Tomato (Solanum lycopersicum L.), one of the most widely grown vegetables worldwide, is susceptible to damping-off and root rot caused by Pythium aphanidermatum (Edson) Fitzpatrick. In in vitro assays, five Trichoderma isolates, viz., Trichoderma harzianum (Th), T. asperellum (Ta), T. virens (Tvs1), T. virens (Tvs2) and T. virens (Tvs3) were compared for their ability to suppress P. aphanidermatum. The mycelial growth of the pathogen was inhibited in vitro after placing each Trichoderma species and isolates on the opposite sides of the same Petri dish. Trichoderma isolates were able not only to arrest the spread of the pathogen but also invade the surface of its colony and sporulate over the colony. Additionally, conidia of Trichoderma isolates were able to inhibit the germination of zoospores of P. aphanidermatum in vitro. Control of tomato damping-off and root rot diseases by soil treatment with the inoculum preparations of Trichoderma isolates employed either alone or in combination was attempted. In greenhouse experiment, the combined inoculation of five Trichoderma isolates suppressed damping-off induced by P. aphanidermatum and increased the survival of tomato plants by 74.5%. In field experiment, the possibility of reducing plant death resulting from root rot disease caused by P. aphanidermatum using Trichoderma isolates, employed either alone or in combination, was investigated. The combined inoculation of five Trichoderma isolates was the most effective treatment, decreasing root rot by 57.2% and increasing the survival of tomato plants by 87.5%. The tested Trichoderma isolates stimulated systemic defence responses in tomato plants grown in the field by activating defence enzymes including peroxidase, polyphenoloxidase and chitinase. Additionally, the chlorophyll contents in the leaves of treated tomato plants were markedly increased. Moreover, the combined inoculation of the five isolates yielded the highest records of growth parameters and fruit yield compared with individual inoculation. Therefore, it was concluded that the mixture containing Trichoderma species and isolates may be used to control damping-off and root rot of tomato caused by Pythium aphanidermatum.

In search of an effective biological control agent against the tomato pathogen Fusarium oxysporum f. sp. lycopersici, rhizospheric soil samples were collected from eight agro-ecological zones of Bangladesh. Among the bacteria isolated from soil, 24 isolates were randomly selected and evaluated for their antagonistic activity against F. oxysporum f. sp. lycopersici. The two promising antagonistic isolates were identified as Brevundimonas olei and Bacillus methylotrophicus based on morphological, biochemical and molecular characteristics. These two isolates were evaluated for their biocontrol activity and growth promotion of two tomato cultivars (cv. Pusa Rubi and Ratan) for two consecutive years. Treatment of Pusa Rubi and Ratan seeds with B. olei prior to inoculation of pathogen caused 44.99% and 41.91% disease inhibition respectively compared to the untreated but pathogen-inoculated control plants. However, treatment of Pusa Rubi and Ratan seeds with B. methylotrophicus caused 24.99% and 39.20% disease inhibition respectively. Furthermore, both the isolates enhanced the growth of tomato plants. The study revealed that these indigenous bacterial isolates can be used as an effective biocontrol agent against Fusarium wilt of tomato.

The Chittering strain of potato spindle tuber viroid (PSTVd) infects solanaceous crops and wild plants in the subtropical Gascoyne Horticultural District of Western Australia. Classical PSTVd indicator hosts tomato cultivar Rutgers (R) and potato cultivar Russet Burbank (RB) and currently widely grown tomato cultivars Petula (P) and Swanson (S) and potato cultivars Nadine (N) and Atlantic (A) were inoculated with this strain to study its pathogenicity, quantify fruit or tuber yield losses, and establish whether tomato strains might threaten potato production. In potato foliage, infection caused spindly stems, an upright growth habit, leaves with ruffled margins and reduced size, and upward rolling and twisting of terminal leaflets (RB, A, and N); axillary shoot proliferation (A); severe plant stunting (N and RB); and necrotic spotting of petioles and stems (RB). Tubers from infected plants were tiny (N) or small and “spindle shaped” with (A) or without (RB) cracking. Potato foliage dry weight biomass was decreased by 30 to 44% in A and RB and 37% in N, whereas tuber yield was diminished by 50 to 89% in A, 69 to 71% in RB, and 90% in N. In tomato foliage, infection caused epinasty and rugosity in apical leaves, leaf chlorosis, and plant stunting (S, P, and N); cupped leaves (S and P); and reduced leaf size, flower abortion, and necrosis of midribs, petioles, and stems (R). Mean tomato fruit size was greatly decreased in all three cultivars. Tomato foliage dry weight biomass was diminished by 40 to 53% (P), 42% (S), and 37 to 51% (R). Tomato fruit yield was decreased by 60 to 76% (P), 52% (S), and 64 to 89% (R), respectively. Thus, the tomato strain studied was highly pathogenic to classical indicator and representative current tomato and potato cultivars, causing major losses in fruit and tuber yields. Tomato PSTVd strains, therefore, pose a threat to tomato and potato industries worldwide.

Alternaria solani is the causal agent of early blight disease in tomatoes (Solanum lycopersicum) and every year is responsible for significant economic losses suffered worldwide by the producers of this crop. Since salicylic acid and Bacillus subtilis are resistance-inducing agents in plants, they were evaluated in order to know their effect on the infection caused by early blight in the tomato crop. Plants of 75 days old were transplanted in furrows 8 m wide by 43.2 m long, the exogenous application of treatments were made, growth variables (plant height and stem diameter), yield (total fruits) and damage in tomato plants were evaluated. The results show significant statistical differences between treatments compared with the control (P≤0.000). B. subtilis applied to the root and salicylic acid applied to the foliage, reduced the severity of A. solani in tomato plants, and caused a significant increment in the crop growth and yield. The use of resistance inducers can represent an alternative of sustainable production and efficient control against pathogens, aimed at reducing the use of agrochemicals and production costs. | Alternaria solani is the causal agent of early blight disease in tomatoes (Solanum lycopersicum) and every year is responsible for significant economic losses suffered worldwide by the producers of this crop. Since salicylic acid and Bacillus subtilis are resistance-inducing agents in plants, they were evaluated in order to know their effect on the infection caused by early blight in the tomato crop. Plants of 75 days old were transplanted in furrows 8 m wide by 43.2 m long, the exogenous application of treatments were made, growth variables (plant height and stem diameter), yield (total fruits) and damage in tomato plants were evaluated. The results show significant statistical differences between treatments compared with the control (P≤0.000). B. subtilis applied to the root and salicylic acid applied to the foliage, reduced the severity of A. solani in tomato plants, and caused a significant increment in the crop growth and yield. The use of resistance inducers can represent an alternative of sustainable production and efficient control against pathogens, aimed at reducing the use of agrochemicals and production costs.

Ionizing radiation is ubiquitous in the environment and can cause mutagenesis in living organisms. In this study, we examined the effects of neutron irradiation on tomato plants. Neutron irradiation decreased tomato germination rates, but most irradiated tomato plants did not show any significant phenotype. However, tomato mutants infected by Tomato yellow leaf curl virus (TYLCV) displayed resistance against TYLCV compared to the wild type (WT), which showed disease symptoms. RNA‐Seq data demonstrated that the expression profiles of eight tomato mutants were significantly different from that of the WT. The transcriptomes obtained from presoaked seeds were highly altered compared to those of dry seeds. Increased irradiation time resulted in severe changes in the tomato transcriptome; however, different neutron irradiation intensities affected the expressions of different sets of genes. A high number of single‐nucleotide polymorphisms in tomato transcriptomes suggest that neutron irradiation strongly impacts plant transcriptomes. The transition/transversion values among mutants were almost constant and were lower than that of the non‐irradiated sample (WT), suggesting that neutron irradiation caused an effect. Taken together, this is the first report showing the effects of neutron irradiation on tomato plants by transcriptome analyses.

Sustainable production of tomato (Solanum lycopersicum L.) under high tunnels is threatened by bacterial wilt (caused by Ralstonia solanacearum) and root-knot nematode (Meloidogyne spp.). Knowledge was generated about the concomitant occurrence of these diseases from January to September 2016, and knowledge and experience of farmers about practices to control them were investigated. The study involved a survey during which 32 farmer groups in 6 subcounties of Kiambu County, Kenya, were interviewed. About 78.1% of high tunnels were in use for 1–2 years and 62.5% of farmers taking part in the study could identify symptoms caused by both causal organisms, which resulted in crop loss of 50%–100%. Seventy-one percent of respondents had positive feelings about high tunnel tomato production. About 82.6% had the soil in which they produced tomato in the tunnels analyzed for nutrition and presence of pathologens, but the majority (71.7%) never followed recommendations on how to amend their soils nutritionally and against the major soil-borne diseases. These findings indicate that more research and information are required so that farmers can optimize high tunnel production of tomato under tropical conditions.

Abstract Rhizobacteria have been reported as bioagents of bacterial diseases and plant growth promoters. The present in vitro study and greenhouse experiment aimed to evaluate the efficiency of Bacillus subtilis, B. amyloliquefaciens, Pseudomonas fluorescens, and P. aeruginosa for the control of bacterial wilt caused by Clavibacter michiganensis subsp. michiganensis and promoting the growth of tomato plants. Effect of formulated and cell suspensions on disease reduction and the pathogen colonization frequency in plants were assessed. The tested bacterial species were able to inhibit the growth of the causal pathogen in vitro. Under greenhouse conditions, the highest reduction in disease severity was detected in tomato plants treated with formulated B. amyloliquefaciens (74.4%), followed by P. aeruginosa (66.7%), while the lowest reduction occurred in tomato seedlings treated with cell suspensions of P. fluorescens (40%) and B. subtilis (53.3%). The four bacterial species produced siderophores, hydrogen cyanide and indole acetic acid in different concentrations. The study confirmed that the use of the four bacterial species as suspensions or formulations could be applied as future eco-friendly alternatives to the synthetic fungicides for controlling the bacterial wilt of tomato caused by C. michiganensis subsp. michiganensis.