فراس علي أحمد الركابي

Pectobacterium carotovorum is one of the most serious pectolytic bacterial pathogens causing significant pre- and postharvest soft rot diseases on a variety of agroeconomic fruits and vegetables worldwide. Application of chemical pesticides for controlling the postharvest diseases is still insufficient and unacceptable by consumers. The effect of sodium benzoate (C6H5COONa) (SBN) was evaluated against the growth of P. carotovorum utilizing the highly pathogenic strain BR03, confirmed molecularly using dnaA primers. The inhibition zone was the greatest when P. carotovorum was treated with 600 mM SBN both at pH 7.5 and 7.0. Flow cytometry (distinguishing live and dead bacterial cells) and the development of bacterial colonies on Petri plates confirmed the bactericidal action of SBN. In addition, these results validated that bacterial cells were killed when treated with 600 mM SBN. The biofilm formation was completely inhibited and destroyed following exposure to 600 mM SBN after a 24-h incubation period and the absorbance readings were reduced as the concentration of SBN increased. Disease severity on inoculated tomato fruits decreased in comparison with the control fruit at either 4 or 25 °C. SBN is safe for human health and commonly used in industries as a food preservative. SBN can be an effective alternative method for controlling soft rot diseases on tomato fruits.

Background: The green peach aphid, Myzus persicae Sulzer, and the bean aphid, Aphis fabae Scopoli (both Hemiptera: Aphididae), are serious pests of greenhouse vegetable crops in Iraq and other regions of the globe. In this study, two morphological identical isolates (AA80 and AA82) of the entomopathogenic fungus Clonostachys rosea Schroers (Hypocreales: Bionectriaceae) from Iraq were isolated and characterized with phylogenetic analysis based on the internal transcribed spacer (ITS) region. The efficacy of C. rosea against M. persicae and A. fabae was previously unknown. Results: In the laboratory bioassays, mortality of adult M. persicae and A. fabae caused by both C. rosea isolates varied according to conidial concentrations, with complete mortality occurring at 1 × 109 conidia ml− 1 10 day post treatment. For M. persicae, LC50 values of AA80 and AA80 isolates were 3.6 × 106 and 3.8 × 106 conidia ml− 1. For A. fabae, LC50 values of AA80 and AA80 isolates were 4.5 × 106 and 4.35 × 106 conidia ml− 1. Infection by both fungal isolates at LC50 values reduced total fecundity of the treated aphids by 20% when compared to the untreated aphids. Conclusions: The results from laboratory bioassays showed that C. rosea has potential as a biological control agent of M. persicae and A. fabae which is crucial for ecofriendly biopesticide development. However, further field and greenhouse studies are required for mass production. Keywords: Myzus persicae, Aphis fabae, Phylogenetic analysis, Virulence, Biological control

Potassium tetraborate tetrahydrate, B4K2O7$4H2O (PTB), was as- sessed as a preharvest spray in the greenhouse for reducing gray mold of tomato fruit caused by Botrytis cinerea. Efficacy of PTB was compared with a natural proprietary product formulated by Agrichem, which was previously shown to inhibit mycelial growth of B. cinerea in vitro and was used as a positive control for green- house studies. Mycelial growth and spore germination of B. cinerea were completely inhibited in vitro by PTB at 25 mM. Phytotoxicity was not observed on treated tomato plants with PTB at 25 mM. Preharvest sprays were applied at three ripening stages: turning, pink, and light red. After fruit reached the final ripening stage, all fruits were harvested and stored for 10 days at either 4 or 25C. Disease severity was reduced compared with controls after storage at either temperature when PTB was applied at the turning stage. Preharvest applications of PTB improved the marketable quality of postharvest tomato fruit and significantly reduced the incidence of gray mold in comparison with inoculated control plants, which received no preharvest fungicidal treatment.

Pectobacterium species cause serious bacterial soft rot diseases worldwide on economically important fruit and vegetable crops including tomato and potato. Accurate and simple methods are essential for rapid pathogen identification and timely management of the diseases. Recombinase polymerase amplification (RPA) combined with a lateral flow device (LFD) was developed for specific detection of Pectobacterium sp. directly from infected plant materials with no need for DNA isolation. The specificity of RPA-LFD was tested with 26 Pectobacterium sp. strains and 12 non-Pectobacterium species and no false positive or false negative outcomes were observed. RPA primers and probe for host control were also developed to detect the host genome for enhanced reliability and accuracy of the developed assay. The detection limit of 10 fg was obtained with both sensitivity and spiked sensitivity assays. No inhibitory effects were observed on the RPA assay when targets (pathogen and host) were directly detected from infected potato and tomato sap. The developed RPA assay has numerous applications from routine diagnostics at point-of-care, biosecurity, surveillance and disease management to epidemiological studies. In addition, this tool can also be used to discover reservoir hosts for Pectobacterium species.

Soft rot caused by Pectobacterium carotovorum is one of most common bacterial diseases occurring in fruits and vegetables worldwide, yet consumer-acceptable options for post-harvest disease management are still insufficient. We evaluated the effect of potassium tetraborate tetrahydrate (B4K2O7.4H2O) (PTB) on the growth of P. carotovorum using strain BA17 as a representative of high virulence. Complete inhibition of bacterial growth was achieved by treatment with PTB at 100 mM both at pH 9.2 and after adjustment to pH 7.0. Bactericidal activity was quantified and validated by counting fluorescently labeled live and dead bacterial cells using flow cytometry, and reconfirmed using qPCR with high-affinity photoreactive DNA binding dye propidium monoazide (PMA). The results of flow cytometry, qPCR, and culturing confirmed that bacterial cells were killed following exposure to PTB at 100 mM. Bacterial cell membranes were damaged following a 5-min treatment and extrusion of cytoplasmic material from bacterial cells was observed using electronic transmission microscopy. Soft rot incidence on inoculated tomato fruit was significantly reduced by dipping infected fruits in PTB at 100 mM for 5 min and no lesions developed following a 10-min treatment. PTB does not pose a hazard to human health and is an effective alternative to other bactericides and antibiotics for controlling soft rot disease of tomato caused by P. carotovorum.

Grey mold is the one of most important postharvest disease of tomato fruit worldwide. Treatments with edible, natural products are needed to reduce losses and contribute to food sustainability. Based on the hypothesis that inhibition of Botrytis spore germination will significantly reduce postharvest losses, botanicals were tested for their  effects on conidia. Ten Botrytis isolates from rotting tomato fruit collected at seventeen different sites in Hawaii were identified morphologically and confirmed by DNA sequence analysis. Effects of plant extracts on spore germination  were assessed at several dilutions. Leaves of candidate biocontrol plants were frozen at -20°C and plant fluids  were sterilized by passing through a 0.22 µm millipore. The effect of plant extracts on germination of Botrytis spores (106/ml) in sterile malt extract broth was evaluated in multi-well microplates using preparations ranging from 10  to 40%. Changes in absorbance measured at 6, 12, and 24 hours after inoculation were analyzed with Gen5 software. Capsicum chinense cultivars Datil and C. annuum Carnival completely inhibited fungal germination at all evaluation times. Extracts from Capsicum species were superior to all other extracts tested. Treatments with 40%  extracts increased the generation of intercellular reactive oxygen species in the fungal conidia. Plasma membrane  damage was shown with fluorescence microscopy when extract-treated conidia were stained with propidium iodide.  Loss of integrity in the spore plasma membrane appears to account for the inhibition of Botrytis spore germination. Extracts from the two pepper cultivars, Datil and Carnival, showed promise as pre-harvest sprays in the greenhouse  and as edible coatings on tomato fruit postharvest to reduce grey mold.

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