Soft rot symptoms were observed on potato plants in several potato cultivars in the western part of Algeria. A total of four strains of Erwinia are devided as follow: i) three strains of bacteria isolated from diseased tissues and soil, identified as Erwinia carotovora subsp carotovorum using conventional bacteriological and biochemical methods; and ii) one strain as Erwinia sp, not pathogens. In vitro tests, on tuber slices were set up to determine slices weight lost, which allows to find differences in cultivar susceptibility and isolate aggressiveness. Among the five cultivars, Laura was the most susceptible than the others tested cultivars. Moreover, it was found that MAI isolate was the most virulent than the other bacterial isolates. The results of this study should allow an optimization of the potato storage, after considering the susceptibility of a given cultivar to soft rot development and the aggressiveness.
Plant extracts and essential oils are promising new sources of non-toxic alternatives to chemicals substances. They are used for their antimicrobial properties against plant diseases of fungal origin, against bacterial, and those of virus origin. This study was carried out to study the antifungal activity of Artemisia herba-alba, Foeniculum vulgare and Citrus sinensis essential oils against Fusarium oxysporum f. sp. albedinis. Essential oil was extracted by steam distillation. Antifungal activity of essential oil was investigated by macro-broth method of dilution by a minimal inhibitory concentration (MIC) assay against this pathogen. The yield of essential oil obtained by steam distillation of Foeniculum vulgare samples was 2.31% greater than that obtained from Citrus sinensis sample which was 1.8%, followed by Artemisia herba alba samples 1.22%. Regarding antifungal activity, the results revealed a better inhibitory activity of Artemisia herba alba against the tested strainsat the lowest LC50 values (0.1 µl/ml). On the other hand, Foeniculum vulgare, Artemisia herba alba and Citrus sinensis essential oils show similar MICs of mycelial growth against this pathogen. The value of the MIC and CMF is greater than 50 µl/ml for the three essential oils.
A greenhouse experiment was conducted to investigate the effect of different levels of NaCl salt on tomato upon B. cinerea infection the causal agent of gray mold disease. The disease assessment was recorded after inoculation by using the scale based on percentage leaf area affected, and the growth of the plants was recorded for each treatment. Three weeks after inoculation by conidial suspension, the estimated disease severity on plants of tomato was 35.18% compared to the control. The highest incidence disease increase of gray mold (39.21%) was obtained with using 300 mM of NaCl after inoculation with B. cinerea compared with the other concentrations and as well as distilled water. Under severe salt stress (150 and 300mM) increased susceptibility of gray mold disease severity were observed in plants inoculated with B. cinerea, while under mild salt stress (50mM of NaCl) this effect was reversed. The treatment of plant by B.cinerea has reduced the growth of the aerial part of tomato plants (39.06%) after three weeks inoculation compared to the control. Three levels of NaCl (50, 100 and 150mM) increased respectively the plant height from 12.73 to 29.84%, 0.28 to 27.16% for the fresh eight and 5.75 to 33.35% for dry weight compared to the plants inoculated and irrigated by distilled water. NaCl addition at 300mM on plants inoculated with B. cinerea decreased the height, fresh weight and dry weight at 0.99, 4.45 and 11.01% respectively.
<p>In this study, which takes place in the northeast of Algeria at the region of Guelma between January 2016 and June 2017, we were able to follow the spatio-temporal evolution of the main hemipteran pests in an orchard of citrus (orange variety). This monitoring showed the presence of 12 hemipteran species, their appearance in the orchard is closely linked to the sap flow. The most abundant species was <em>Aleurothrixus floccosus</em>. The number of the other species that found was very small or absent in most of the time. We also noted that <em>Aonidiella aurantii</em> and <em>Chrysomphalus dictyospermi</em> had a preference to develop in the center of the tree while the other species found, which are: <em>Dialeurodes citri, Aphis gossypii</em>, <em>Aphis spiraecola</em>, <em>Lepidosaphes beckii, Parlatoria ziziphi, Saissetia olea, Coccus hesperidum</em>, <em>Coccus pseudomagnoliarum</em> and <em>Icerya purchasi</em>, were found in the sunniest parts of the tree.<br /><strong> </strong></p>
Background The development of ecofriendly tools against plant diseases is an important issue in crop protection. Screening and selection process of bacterial strains antagonists of 2 pathogenic bacterial species that limit very important crops, Erwinia amylovora, the causal agent of the fire blight disease, and Pectobacterium carotovorum, the causal agent of bacterial potato soft rot, were reported. Bacterial colonies were isolated from different ecological niches, where both pathogens were found: rhizosphere of potato tubers and fruits and leaves of pear trees from the northwest region of Algeria. Direct and indirect confrontation tests against strains of E. amylovora and P. carotovorum were performed. Results Results showed a significant antagonistic activity against both phytopathogenic species, using direct confrontation method and supernatants of cultures (p<0.005). In vitro assays showed growth inhibitions of both phytopathogenic species. Furthermore, results revealed that the strains of S. plymuthica had a better inhibitory effect than the strains of P. fluorescens against both pathogens. In vivo results on immature pear fruits showed a significant decrease in the progression of the fire blight symptoms, with a variation in the infection index from one antagonistic strain to another between 31.3 and 50%, and slice of potato showed total inhibition of the pathogen (P. carotovorum) by the antagonistic strains of Serratia plymuthica (p<0.005). Conclusion This study highlighted that the effective bacteria did not show any infection signs towards plant tissue, and considered as a potential strategy to limit the fire blight and soft rot diseases.
Thyme (Thymus sp.), a medicinal plant of the family Lamiaceae, is used in traditional medicine, contains a wide array of medicinally active components, in their great majority of a rather complex mixture of thymol, ρ-Cymene, γ-Terpinene, β-Caryophyllen, etc. This study aimed to evaluate the efficacy of Thymus vulgaris extract against Fusarium oxysporum f. sp.radicis-lycopersici strain under saline conditions, assuming soil with high salt content of the arid regions. Essential oil was extracted by hydrodistillation technique using a Clevenger apparatus. The essential oil compounds were identified by GC-MS analysis. Antifungal activity of essential oil against Fusarium oxysporum f. sp. radicis-lycopersici was investigated by agar dilution method. The main constituents of thyme essential oil were thymol (76.96 %), ρ-cymene (9.89 %) and γ-Terpinene (1.92 %). Essential oil from Thymus resented high in vitro activity, in controlling conidial germination and mycelial growth. However, the oil was significantly not active against the spore production under a salinity medium. The results showed that mycelial growth was stimulated in concentrations with 0.6 -1.5 %. In contrast, it was significantly reduced at a higher concentration (2 %). The application of NaCl caused a significant increase in the conidia production at various concentrations tested. NaCl has a minor inhibitory effect on conidial germination only when the concentration was 2 %. The results of this study indicate that salinity decreases the efficacy of essential oil against the pathogen.
The present research was taken out to assess the physiological, biochemical, and photosynthetic responses of the chickpea (Cicer arietinum L) to the combination of clay-bentonite and saline water in greenhouse conditions, at four concentrations of NaCl (0, 50, 100 and 200 mM). A substantial decrease in all the studied parameters (germination rate, root and stem length, fresh weight or dry weight, relative water content and chlorophyll content) was observed when salinity was increased. However, the application of various NaCl concentrations improved the total soluble protein and soluble sugar content in plants cultivated in the substrate without bentonite. The imposition of 50 mM NaCl with bentonite increased total soluble protein content. In contrast, the 100 and 200 mM treatment led to decreased total soluble protein content. The use of the bentonite did not produce any changes into depreciating of the effect of NaCl stress. On the other hand, salinity-bentonite exacerbated a reduction in physiological and biochemical processes of chickpea. Indeed, the K+/Na+ ratio decreased in all organs of plants with increasing NaCl doses. This ratio is slightly in favor of K+ only in substrate without bentonite. Our findings indicated that salinity-bentonite exacerbated a reduction in physiological and biochemical processes.
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