Tomato (Lycopersicon esculentum) is one of the widely grown vegetables worldwide. Fusarium oxysporum f. sp. lycopersici (FOL) is the significant contributory pathogen of tomato vascular wilt. The initial symptoms of the disease appear in the lower leaves gradually, trail by wilting of the plants. It has been reported that FOL penetrates the tomato plant, colonizing and leaving the vascular tissue dark brown, and this discoloration extends to the apex, leading to the plants wilting, collapsing and dying. Therefore, it has been widely accepted that wilting caused by this fungus is the result of a combination of various physiological activities, including the accumulation of fungal mycelia in and around xylem, mycotoxin production, inactivation of host defense, and the production of tyloses; however, wilting symptoms are variable. Therefore, the selection of molecular markers may be a more effective means of screening tomato races. Several studies on the detection of FOL have been carried out and have suggested the potency of the technique for diagnosing FOL. This review focuses on biology and variability of FOL, understanding and presenting a holistic picture of the vascular wilt disease of tomato in relation to disease model, biology, virulence. We conclude that genomic and proteomic approachesare greater tools for identification of informative candidates involved in pathogenicity, which can be considered as one of the approaches in managing the disease.

In the present study, 43 isolates of Phosphate solubilizing rhizobacteria (PSRB) were isolated from 37 rhizospheric soil samples of tomato collected from tomato growing regions of Karnataka. Among the 43 isolates, 33 were found to be positive for solubilizing both inorganic and organic forms of phosphorous. The isolates were analyzed for their ability to colonize roots of tomato and to increase the seed quality parameters under laboratory conditions. On the basis of above criteria, 16 isolates were selected for further studies. Organic acids from PSRB isolates were analyzed and phytase zymogram for two isolates viz., PSRB21 and 31 was prepared. Under greenhouse conditions, all selected isolates showed increased shoot length, root length, fresh weight, dry weight and phosphorous content of tomato seedlings to various extent with respect to control. Analysis of pH and available phosphorous in rhizosphere soil samples of 30 dayold-seedlings revealed that the available phosphorous content was high in rhizospheric soil samples of plants raised from seeds bacterized with PSRB isolates over control. Even though all selected PSRB's were able to increase the plant growth, only few of them showed protection against fusarium wilt and none of them against early blight.

The present study aimed at the molecular characterization of pathogenic and non pathogenic F. oxysporum f. sp. lycopersici strains isolated from tomato. The causal agent isolated from symptomatic plants and soil samples was identified based on morphological and molecular analyses. Pathogenicity testing of 69 strains on five susceptible tomato varieties showed 45% of the strains were highly virulent and 30% were moderately virulent. Molecular analysis based on the fingerprints obtained through ISSR indicated the presence of wide genetic diversity among the strains. Phylogenetic analysis based on ITS sequences showed the presence of at least four evolutionary lineages of the pathogen. The clustering of F. oxysporum with non pathogenic isolates and with the members of other formae speciales indicated polyphyletic origin of F. oxysporum f. sp. lycopersici. Further analysis revealed intraspecies variability and nucleotide insertions or deletions in the ITS region among the strains in the study and the observed variations were found to be clade specific. The high genetic diversity in the pathogen population demands for development of effective resistance breeding programs in tomato. Among the pathogenic strains tested, toxigenic strains harbored the Fum1 gene clearly indicating that the strains infecting tomato crops have the potential to produce Fumonisin.

Plants respond to bacterial pathogen attack by activating various defence responses, which are associated with the accumulation of several factors like defencerelated enzymes and inhibitors which serve to prevent pathogen infection. The present study focused on the role of the defence-related enzymes phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) in imparting resistance to tomato against bacterial wilt pathogen Ralstonia solanacearum. The temporal pattern of induction of these enzymes showed maximum activity at 12 h and 15 h for PAL and PPO, respectively, after the pathogen inoculation (hpi) in resistant cultivars. Twenty different tomato cultivars were analyzed for PAL, PPO and total phenol content following pathogen inoculation. The enzyme activities and total phenol content increased significantly (P < 0.05) in resistant cultivars upon pathogen inoculation. The increase in enzyme activities and total phenol content were not significant in susceptible and highly susceptible cultivars. The role of PAL and PPO in imparting resistance to tomato against bacterial wilt disease is discussed.

Field surveys undertaken in major tomato growing districts of the Karnataka state, located in southern part of India, revealed a high incidence of bacterial wilt caused by Ralstonia solanacearum and it is one of the most destructive bacterial diseases of economically important crops. Across all the tomato cultivars under evaluation, the disease incidence in plants ranged from 9% to 39% whereas the incidence in seeds ranged from 4% to 18%. The effects of tomato seed treatments with Pseudomonas fluorescens in the control of bacterial wilt under greenhouse conditions revealed that the treatments protected plants against soil-borne infections of the bacterial wilt organism. Seed treatment with antagonistic P. fluorescens strain significantly improved the quality of seed germination and seedling vigour. The disease incidence was significantly reduced in plants raised from P. fluorescens treated seeds followed by challenge inoculation with R. solanacearum. Periodic field surveys for the incidence of bacterial wilt of tomato could be recommended to monitor the populations of the bacterial wilt pathogen. Workable measures are presented that could lead to the reduction of the prevalence of this serious disease in affected fields of the small farm-holders.

The present method provided rapid and reliable detection of fumonisin-producing Fusarium spp. The mPCR assay could be an alternative strategy to current conventional mycotoxin analytical techniques and a reliable tool for high-throughput monitoring of major mycotoxin-producing fungi during the processing steps of food and feed commodities.

Cinnamomum verum plant extract mediated propellant chemistry route was used for the green synthesis of zinc oxide nanoparticles. Prepared samples were confirmed for their nano regime using advanced characterization techniques such as powder X-ray diffraction and microscopic techniques such as scanning electron microscopy and transmission electron microscopy. The energy band gap of the green synthesized zinc oxide (ZnO)-nanoparticles (NPs) were found between 3.25–3.28 eV. Fourier transmission infrared spectroscopy shows the presence of Zn-O bond within the wave number of 500 cm−1. SEM images show the specific agglomeration of particles which was also confirmed by TEM studies. The green synthesized ZnO-NPs inhibited the growth of Escherichia coli and Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 125 µg mL−1 and 62.5 µg mL−1, respectively. The results indicate the prepared ZnO-NPs can be used as a potential antimicrobial agent against harmful pathogens.

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