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Cucumber root and stem rot disease caused by Fusarium oxysporum f. sp. radicis-cucumerinum (Forc) is one of the most important diseases of cucumber in Iran. In this regard, this study aimed to investigate the antifungal activity of some chemical salts against Forc in in vitro and greenhouse conditions. The experiment layout in the in vitro condition was based on a factorial experiment using a completely randomized design including three replications. Treatments included potassium sorbate (PS), mono-potassium phosphite, ammonium bicarbonate, salicylic acid (SA), di-potassium hydrogen phosphate (DPHP), and fungicide carbendazim (CAR) (Bavistin WP 60%) at 0, 0.5, 2, 4, and 5 g/l. In a greenhouse condition, the experiment was conducted using a randomized complete block design with three replications. The laboratory and greenhouse experiments showed that the treatments had a significant effect on fungal growth inhibition and disease severity. In in vitro condition, the highest control of the fungus was attributed to PS and fungicide CAR. Conversely, DPHP had the least control (8.74%) on the growth of Forc at 0.5 g/l. In a greenhouse condition, CAR prevented disease symptoms for one month. However, PS and SA controlled mycelial growth with an efficiency of 61.19 and 39.2%, respectively. Accordingly, it seems that PS and SA are fungitoxic against Forc and can control root and stem rot disease in the greenhouse by root and foliar application.

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Septoria tritici blotch (STB) caused by Zymoseptoria tritici is one of the most important wheat diseases in the world and causes significant annual damage to wheat crops around the globe. The use of resistant cultivars is the most effective method for the management of this disease. Recently, the use of acquired systemic induced resistance has been proposed to manage wheat leaf blotch. In this study, the effect of salicylic acid (SA) on the relative changes of PAL and PR2 gene expression was investigated using qPCR technique. The expressions of catalase, peroxidase, and ascorbate peroxidase enzymes were also assessed in a sensitive wheat cultivar. Controlled and contaminated plants were sampled and compared at 0, 12, 24, 48, 96, and 240 hours after inoculation. The results showed that treatment with salicylic acid significantly reduced the level of disease compared to control plants. Comparison of gene expression patterns also showed that the expression of both PAL and PR2 genes in control and SA pre-treated plants increased after fungal inoculation; however, their expression was significantly higher (2.6 and 1.3 folds respectively for PAL and PR2) in plants treated with salicylic acid than the control. Moreover, treatment with salicylic acid significantly affected the activity of all three enzymes. It can be concluded that the high response of PAL and PR2 genes to salicylic acid pre-treatment, as well as increased activity of peroxidase along with the reduced activity of catalase and ascorbate peroxidase enzymes indicate the effective role of SA in inducing wheat resistance against STB.

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The cabbage aphid, Brevicoryne brassicae (Hemiptera: Aphididae), is an important pest of rapeseed. In this study, the effects of a silicon-based fertilizer, silicate potassium (SP), and salicylic acid (SA) on inducing resistance in rapeseed to the aphid were studied under field conditions. The rapeseed plants were directly sprayed with SP and SA at two application rates, and the population density of alive and parasitized aphids by Diaeretiella rapae (Hymenoptera: Braconidae) was recorded every three days. The results showed that the aphid population densities in SP and SA treatments were significantly lower than in control (2.21 and 3.53 folds, respectively). The lowest population density was observed in the SP treatment (1200 g/ ha). Moreover, the parasitized aphid densities in the treatments were significantly increased, and the highest parasitism was recorded in the SP treatment (1200 g/ha). The rapeseed yield in the SP-treated plants was significantly more than control, and the highest yield increase was observed in SP treatment (1200 g/ha). According to the results, SP at 1200 g/ha is recommended for cultural control of B. brassicae in the rapeseed fields.

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Different defense pathways in plants evolved in reaction to pathogens. The main aim of this study was to investigate the mechanism of action of glyphosate in resistance induction to bacterial phytopathogens. To do so, glyphosate at an optimal concentration of 1.8 mg / l was used on transgenic potato, to induce resistance to two strains of pathogenic bacteria (21A of Pectobacterium atrosepticum and ENA49 of Dickeya dadantii). It was been shown that plant defense responses to pathogens can be stimulated by treatment plants at an optimal concentration of glyphosate. Transgenic potato leaves infected with potato pathogenic bacteria, and then treated with glyphosate showed a high level of expression of pathogenesis-related genes (PR-2, PR-3, PR-5), especially PR-2 gene and defense response genes (HSR-203j, HIN1), especially HSR-203j gene. The expression of PR-2 gene in leaves infected with these two bacteria were 1.5 and 2.9 times, for PR-3 gene 1.7 and 1.7 times, for PR-5 gene to 1.3 and 1.5 times and expression of HSR-203J gene to 2.5 and 2.4 times and - HIN1 gene to 1.7 and 1.7 times, with Dickeya dadantii and Pectobacterium atrosepticum infection, respectively. The expression of these genes in control samples didn’t significantly change. The results showed that there was a significant difference between the expression of genes in the experimental and control samples (plants treated by glyphosate compared to untreated plants). The results showed that the treatment of plants by glyphosate can induce a systemic acquired resistance to phytopathogens by inducing proteins and defense response genes.

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The main postharvest problems of persimmon in Iran are severe softening and disease incidence on the fruits during storage. Therefore, delay in softening and/or control of diseases result in the storage life extension of persimmon fruit. The strategy of induced disease resistance in plants by biotic and abiotic treatments is an attractive method for controlling diseases. Salicylic acid (SA) is a well known natural inducer of disease resistance in plants. In this study persimmon fruits cv. Karaj were treated at harvest with SA at 0 (as control), 1 and 2 mM and the quality parameters of the fruit were measured during 3 months of storage at monthly intervals. The most noticeable effect of postharvest SA application on stored persimmon fruit was the reduction of disease incidence at 2 mM concentration, while 1 mM SA failed to control diseases. Results showed that SA did not affect TSS, titratable acidity, soluble tannin content, and fruit firmness. Also, SA could not suppress ethylene production compared to the control. SA treatment at 2 mM concentration reduced postharvest disease incidence of persimmon fruit by inducible defense mechanism, being suitable for increasing postharvest life of the fruit.