AvrPto and AvrPtoB are type III effector proteins expressed by Pseudomonas syringae pv. tomato strain DC3000, a pathogen of both tomato and Arabidopsis spp. Each effector physically interacts with the tomato Pto kinase and elicits a hypersensitive response when expressed in tomato leaves containing Pto. An avrPto deletion mutant of DC3000 previously was shown to retain avirulence activity on Pto-expressing tomato plants. We developed an avrPtoB deletion mutant of DC3000 and found that it also retains Pto-specific avirulence on tomato. These observations suggested that avrPto and avrPtoB both contribute to avirulence. To test this hypothesis, we developed an ΔavrPtoΔavrPtoB double mutant in DC3000. This double mutant was able to cause disease on a Pto-expressing tomato line. Thus, avrPto and avrPtoB are the only avirulence genes in DC3000 that elicit Pto-mediated defense responses in tomato. When inoculated onto susceptible tomato leaves and compared with wild-type DC3000, the mutants DC3000ΔavrPto and DC3000ΔavrPtoB each caused slightly less severe disease symptoms, although their growth rate was unaffected. However, DC3000ΔavrPtoΔavrPtoB caused even less severe disease symptoms than the single mutants and grew more slowly than them on susceptible leaves. Our results indicate that AvrPto and AvrPtoB have phenotypically redundant avirulence activity on Pto-expressing tomato and additive virulence activities on susceptible tomato plants.

A soft rot of fruits caused by Mucor racemosus occurred on cherry tomato collected in Agricultural Products Wholesale Market in Jinju, Korea. The disease infection usually occurred wounded areas after cracking of fruits. At first, the lesions started with water soaked and rapidly softened and diseased lesion gradually expanded. Colonies were white to brownish to gray in color. Sporangia were 32~54 ㎛ in size and globose in shape. Sporangiophores were 8~14 ㎛ in width. Sporangiophores were 5~12 × 4~8 ㎛ in size, ellipsoidal to subglobose in shape.

The present study revealed that the use of Pseudomonas aeruginosa and the fungicide Benlate greatly suppressed Fusarium damping off and root rot of Tomato caused by Fusarium solani,Benlat showed high level of antagonism against F. solani and that caused significant reduce in mycelium growth 100% and spores germination 49.53% in laboratory . It was also showed that Benlate has no toxic effect to Ps. aeruginosa while it caused effective suppression to F.,solani where the percentage of mycelium growth inhibition was 100% at 150 mg/L active ingredient of Benlate ,The interaction between Ps. aeruginosa and Benlate caused high suppression to Tomato seedling infection with F.solani in addition to significant increase in plants growth features.

Late blight, caused by the fungal pathogen Phytophthora infestans, is a disease that quickly spreads in tomato fields under suitable weather conditions and can threaten the sustainability of tomato farming in California, USA. This paper explores the applicability of remotely sensed images to detect disease spectral anomalies for precision disease management. We used the indices approach and generated a 5-index image that we used to identify the disease in tomato fields based on information from field-collected spectra and linear combinations of the spectral indices. Field results indicated that we were able to identify five clusters in the image space with small overlaps of a few clusters. Using the identified 5-cluster scheme to classify the tomato field images, we were able to successfully separate the diseased tomatoes from the healthy ones before economic damage was caused. Hence, the method based on a 5-index image may significantly enhance the capability of multispectral remote sensing for disease discrimination at the field level.

Numerous whitefly-transmitted viral diseases of tomato have emerged in countries around the Nile and Mediterranean Basins the last 20 years. These diseases are caused by monopartite geminiviruses (family Geminiviridae) belonging to the genus Begomovirus that probably resulted from numerous recombination events. The molecular biodiversity of these viruses was investigated to better appreciate the role and importance of recombination and to better clarify the phylogenetic relationships and classification of these viruses. The analysis partitioned the tomato-infecting begomoviruses from this region into two major clades, Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus. Phylogenetic and pairwise analyses together with an evaluation for gene conversion were performed from which taxonomic classification and virus biodiversity conclusions were drawn. Six recombination hotspots and three homogeneous zones within the genome were identified among the tomato-infecting isolates and species examined here, suggesting that the recombination events identified were not random occurrences.

Fusarium oxysporum f. sp. lycopersici produces extracellular enzymes known as tomatinase, which degrade the tomato phytoanticipin α-tomatine to less toxic metabolites. Tomatinase gene (FoToml) has been found also in certain strains of F. oxysporum belonging to formae speciales nonpathogenic on tomato plants. In the current study, four FoToml-positive strains (#2, #3, #11, and #17) of F. oxysporum belonging to formae speciales different from f. sp. lycopersici and f. sp. radicis-lycopersici were examined for their ability to infect tomato plants. All of the four strains colonized not only the roots and basal stems but also upper stems of tomato plants. One of the four strains, #3 (f. sp. batatas), was transformed with the β-glucuronidase (GUS) reporter gene. A GUS-marked #3 (#3-GUS) colonized vascular vessels of all tomato cultivars tested differing in the extents of colonization in the stems among the cultivars. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that each FoToml of the four FoToml-positive strains was expressed in the roots and stems of tomato plants, suggesting that FoToml is important for the four strains to survive in tomato plants. To see systemic induction of defense genes in tomato plants inoculated with either #2, #3, #11, or #17, accumulations of transcripts of β-1,3-glucanase and chitinase genes were analyzed. Tomato plants inoculated with #2 or #3 showed enhanced expression of acidic chitinase gene (Chi3). Prior inoculation of tomato plants with either #2 or #3 suppressed the vascular wilt of tomato caused by subsequent challenge with F. oxysporum f. sp. lycopersici.

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (Smith) and bacterial spot caused by Xanthomonas campestris pv. vesicatoria (Doidge) Dye have become important diseases of tomato in Egypt. The present work was planned to evaluate the reaction of different tomato cultivars and the role of seeds to transmit both pathogens. Cultivars of Dora, Flora-Dade, KTM141, Money Maker, Niagra, Super strain B hybrid and GS12 were moderately resistant to both diseases, but Castle rock, Peto 86 and Super strain B cultivars were susceptible. However, Castle rock, Peto 86, Super strain B and Niagra cultivars were highly susceptible for bacterial canker than spot disease. Using the Liquid assay method, C. michiganensis subsp. michiganensis bacterium could be detected in seeds of cultivars Dora, KTM141, Niagra and Super strain B hybrid, but X. campestris pv. vesicatoria was detected on seeds of cultivars GS12, Peto 86 and Super Marmand. However, both bacterial pathogens were not detected in seeds of all cultivars, except GS12, when direct planting method on selective media was used. In an in vivo assay, bacterial canker has developed more than bacterial spot disease on tomato seedlings produced from non-treated seeds. Bacterial canker has developed on all tested cultivars at different frequencies. Transmission of both pathogens occurred at high frequency by seeds of cultivars Niagra and Dora, however bacterial spot was not borne on samples of other tomato cultivars

A severe outbreak of crown and root rot of tomato was observed in greenhouses in Malta in eight locations during the period November 2004 – February 2005. Besides root and crown symptoms, several plants showed cankers at the basal part of the stem. Fusarium oxysporum was constantly isolated from these plants. One isolate from each location was tested for pathogenicity on tomato seedlings. All these isolates caused severe necrotic lesions of the crown and roots, and stem cankers. It was concluded that F. oxysporum f. sp. radicis-lycopersici (FORL) was the cause of the outbreak. Incidence ranged from 10 to 50%. Cold weather conditions occurring in Malta during the late fall and winter of 2004–2005 probably favoured the disease. The use of tomato cultivars or hybrids resistant to FORL is suggested for winter tomato crops in south Mediterranean areas.

Tomato yellow leaf curl (TYLC) is one of the most devastating pathogens affecting tomato (Lycopersicon esculentum) worldwide. The disease is caused by a complex of begomovirus species, two of which, Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV), are responsible for epidemics in Southern Spain. TYLCV also has been reported to cause severe damage to common bean (Phaseolus vulgaris) crops. Pepper (Capsicum annuum) plants collected from commercial crops were found to be infected by isolates of two TYLCV strains: TYLCV-Mld[ES01/99], an isolate of the mild strain similar to other TYLCVs isolated from tomato crops in Spain, and TYLCV-[Alm], an isolate of the more virulent TYLCV type strain, not previously reported in the Iberian Peninsula. In this work, pepper, Nicotiana benthamiana, common bean, and tomato were tested for susceptibility to TYLCV-Mld[ES01/99] and TYLCV-[Alm] by Agrobacterium tumefaciens infiltration, biolistic bombardment, or Bemisia tabaci inoculation. Results indicate that both strains are able to infect plants of these species, including pepper. This is the first time that infection of pepper plants with TYLCV clones has been shown. Implications of pepper infection for the epidemiology of TYLCV are discussed.