Chitosan has been reported to have antimicrobial property to some pathogen species as well as an elicitor of resistance in plants , particularly Systemic Acquired Resistance (SAR). A bioassay of chitosan against Xanthomonas oryzae pv. oryzae (Xoo) was conducted to determine its antimicrobial property against bacterial blight pathogen and the optimum concentration that is most inhibitory to the pathogen. Chitosan was also tested as foliar spray to rice plants to evaluate its potential to induce SAR against bacterial blight disease. Chitosan treatments (300 ppm, 400 ppm, and 500 ppm) possessed antimicrobial property against Xoo in vitro, producing zones of inhibition which were generally significantly bigger than those of the control (streptomycin, acetic acid, and sterile distilled water) at 2, 4, and 6 days after inoculation. Chitosan-sprayed plants showed significantly shorter bacterial blight lesions which were comparable to the plants sprayed with streptomycin, and Boost, a commercial plant defense activator and a known inducer of SAR. Chitosan is found effective in reducing bacterial blight lesions in rice plants due to its antimicrobial property and also most likely due to the induction of SAR.
Bacterial wilt is an important constraint to tomato production. The search for an effective and safe method of managing bacterial wilt is imperative. Chitosan, adeactylated chitin was reported to possess direct antimicrobial property against certain pathogens and is a plant resistance booster. This study was conducted to: evaluate the effectiveness of varying chitosan concentrations and sources against bacterial wilt in vitro and in vivo and compare different application methods in bacterial wilt control. Varying chitosan concentrations (100, 200, 300, 400 and 500 ppm) immersed/dissolved in water, 1% acetic acid, and streptomycin were evaluated against R. solanacearum in laboratory and pot experiments. Three chitosan sources were also evaluated against the pathogen. Different methods of application were compared. Regardless of source, chitosan in water has no direct antimicrobial activity against R.solanacearum but when dissolved 1% acetic acid, it was able to inhibit the bacteria. Inhibition of chitosan/acetic acid was best at 300 ppm and significantly higher than 1% acetic acid alone indicating that its antimicrobial property was enhanced by the acid. Two hundred ppm chitosan/acetic acid-treated plants delayed the onset of disease and produced the lowest percentage infection, lowest disease severity rating, and highest percentage survival in inoculated tomato. The action of 200 ppm chitosan/acetic acid treatment was due to a dual effect, i.e., antimicrobial and as an elicitor of resistance. All application methods were effective in controlling bacterial wilt but one time root dipping to 200 ppm chitosan/acetic acid before transplanting was enough to protect the plants against the disease.
Natural products for disease control and quality enhancement of fruit after harvest are increasingly used as alternative to chemical pesticides which are hazardous to human health and the environment. This study was conducted to extract chitosan from crab processing waste and compare its effect with commercial chitosan (Sigma) on stem-end rot disease and on the quality of carabao mango fruit. FT-IR spectra exhibited characteristic absorption bands of the amides, the amines and the carbonyl occurring as prominent and sharp peaks in both laboratory-produced and the commercial chitosan. In vitro assay of D. natalenses against chitosan showed comparable inhibitory effect on fungal growth and development with that of Dithane (‘mancozeb’). When the extracted and commercial chitosan were dissolved in 2% acetic acid and applied at 0-500 ppm, it was found that chitosan regardless of source and concentration can reduce weight loss in mango during storage. Dipping the fruits at different chitosan concentrations significantly reduced the infection rate of stem-end rot disease. The infection rate in fruits treated with 100 ppm laboratory-produced chitosan was comparable with that of 500 ppm Sigma chitosan. The results of this study suggest that the laboratory-produced chitosan at 100 ppm is comparable with that of Sigma chitosan as they significantly slowed down the infection rate of stem end rot disease caused by D. natalensis. Chitosan’s antimicrobial action and beneficial effects on fruit quality could have far reaching application in the fresh fruit industry.
Edible mushrooms, whether fresh or processed, are widely consumed worldwide. In order to determine their nutritional and/or functional values, this study was conducted to evaluate the free radical scavenging activity of Volvariella (Volvariella volvacea), wood ear (Auricularia auricula-judae), and shiitake (Lentinula edodes) mushrooms. Trolox equivalent per 100g sample (TE/100g) was determined to describe the activity using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Results showed that wood ear exhibited the highest free radical scavenging activity (387.11±30.26 TE/100g) among the three species. Shiitake mushroom exhibited 368.13 ±27.03 TE/100g activity. Volvariella contained the lowest activity with 318.72 ±36.87 TE/100g. Based on the solvent system, ethanolic extracts showed the highest free radical scavenging activity (386.45±23.30 TE/100g) while hexane extract showed the least free radical scavenging activity (326.34 ±27.75 TE/100g). Water extract exhibited 361.17 ±49.11TE/100g activity. The results of this study showed that mushroom extracts could serve as natural antioxidants due to their significant antioxidative property
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