Chitosan Reduces Bacterial Spot Severity and Acts in Phenylpropanoid Metabolism in Tomato Plants
ABSTRACT Chitosan has recently shown potential for the control of plant diseases and can act as an elicitor in the induction of defence mechanisms. This study was made to assess the effect of chitosan on bacterial spot control caused by Xanthomonas gardneri in tomato plants. The chitosans used were commercial (Ccom), low molecular weight (Clmw) and medium molecular weight (Cmmw). Chitosans provided disease protection of up to 56%, with best results from Clmw at 3 mg/ml, applied 3 days prior to bacterial inoculation. The spectrophotometric profile of tomato plants that were treated with Clmw showed an increase of absorbance between wavelengths 280 and 300 mm, indicating that the polysaccharide may have induced the plants into synthesizing different compounds as a response to X. gardneri. The analysis of total phenolic compounds and flavonoids supported the results obtained in spectrophotometric scanning, showing a significant increase of those metabolites 3 days after inoculation. Therefore, chitosan has the capability of controlling bacterial spot in tomato plants, which is thought to be attributable to the induction of defence mechanisms in the plant.
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ABSTRACT: Claims have been made recently that glyphosate-resistant (GR) crops sometimes have mineral deficiencies and increased plant disease. This review evaluates the literature that is germane to these claims. Our conclusions are: (1) although there is conflicting literature on the effects of glyphosate on mineral nutrition on GR crops, most of the literature indicates that mineral nutrition in GR crops is not affected by either the GR trait or by application of glyphosate; (2) most of the available data support the view that neither the GR transgenes nor glyphosate use in GR crops increases crop disease; and (3) yield data on GR crops do not support the hypotheses that there are substantive mineral nutrition or disease problems that are specific to GR crops.Journal of Agricultural and Food Chemistry 09/2012; 60(42). DOI:10.1021/jf302436u
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ABSTRACT: The effectiveness of composted sewage sludge incorporated into Pinus bark-based substrate with or without biofertilizer, fish hydrolyzate, chitosan and Trichoderma asperellum was evaluated for the control of Fusarium wilt in chrysanthemum. The substrate was obtained from pots containing chrysanthemum plants killed by the pathogen. Half of the substrate was sterilized prior to the incorporation of sewage sludge (0, 10%, 20% and 30% v/v). These substrates were or were not supplemented with the following: biofertilizer, fish hydrolyzate and Trichoderma. The mixtures were transferred to pots, and the chrysanthemum was transplanted. For all treatments, half of the plants were sprayed weekly with chitosan. Assessment of severity was performed on the 8th, 12th, 15th and 20th week after transplanting. In the 12th week, microbiological and chemical analysis of the substrate was performed. The incorporation of composted sewage sludge into the Pinus bark-based substrate significantly reduced Fusarium wilt, which was progressively decreased as the concentration of sewage sludge increased. The addition of biofertilizer, fish hydrolyzate, chitosan and Trichoderma had no effect on the disease. The microbial community was greater in non-disinfested substrates. The results indicate that suppressiveness is related to the interaction of chemical and microbiological factors.Tropical Plant Pathology 10/2013; 38(5):414-422. DOI:10.1590/S1982-56762013005000026
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ABSTRACT: Resistance inducers have been used in annual crops as an alternative for disease control. Wood perennial fruit trees, such as those of the citrus species, are candidates for treatment with resistance inducers, such as salicylic acid (SA) and chitosan (CHI). However, the involved mechanisms in resistance induced by elicitors in citrus are currently few known. In the present manuscript, we report information regarding the transcriptional changes observed in sweet orange in response to exogenous applications of SA and CHI using RNA-seq technology. More genes were induced by SA treatment than by CHI treatment. In total, 1,425 differentially expressed genes (DEGs) were identified following treatment with SA, including the important genes WRKY50, PR2, and PR9, which are known to participate in the salicylic acid signaling pathway, and genes involved in ethylene/Jasmonic acid biosynthesis (ACS12, AP2 domain-containing transcription factor, and OPR3). In addition, SA treatment promoted the induction of a subset of genes involved in several metabolic processes, such as redox states and secondary metabolism, which are associated with biotic stress. For CHI treatment, there were 640 DEGs, many of them involved in secondary metabolism. For both SA and CHI treatments, the auxin pathway genes were repressed, but SA treatment promoted induction in the ethylene and jasmonate acid pathway genes, in addition to repressing the abscisic acid pathway genes. Chitosan treatment altered some hormone metabolism pathways. The DEGs were validated by quantitative Real-Time PCR (qRT-PCR), and the results were consistent with the RNA-seq data, with a high correlation between the two analyses. We expanded the available information regarding induced defense by elicitors in a species of Citrus that is susceptible to various diseases and identified the molecular mechanisms by which this defense might be mediated.BMC Genomics 04/2015; 16(1):288. DOI:10.1186/s12864-015-1440-5