| Chitosan is a natural and nontoxic polysaccharide with a long-chain backbone comprised of N-acetyl glucosamine. It has been utilized in soil amendment and seed treatment, as well as foliar treatment to control Fusarium oxysporum, Fusarium acuminatum, Cylindrocladium floridanum, and Aspergillus flavus. Potato tubers are abundant in carbohydrates, protein, cellulose, fat, a variety of vitamins, inorganic salt, and possess high nutritional value. However, potato is susceptible to be infected by pathogen, thereby leading to low yield. Herein, the effects of chitin, chitosan and water soluble chitosan on potato rhizosphere soil, potato quality and potato dry rot were studied, and the antibacterial activity against bacteria and fungi of chitosan and pyridine chitosan’s were also investigated. The experimental results are as follows:(1) The potatoes were Planted in the soil containing 0.5 to 8.0 g/kg of chitin or chitosan, the microbial number and physical chemical index of rhizosphere soil in different growth stages of potato were determined. The results showed that: ① The number of beneficial microorganisms such as bacteria, actinomyc, nitrogen-fixation bacteria significantly increased while the number of fungi reduced at the concentrations of chitin or chitosan ranging from 0.5 to 8 g/kg. ② The content of alkali solution nitrogen, available phosphorus, quick effect potassium and organic matter effectively improved. With the treatment of 2.0 g/kg chitosan and chitin, the number of nitrogen-fixation bacteria, actinomycet, emulsifying bacteria was 3.98 and 2.45,5.49 and 1.82,1.62 and 2.51 times compared to that of the control group during the tillering stage, respectively. ③ In the seedling stage, the contents of solution nitrogen, available phosphorus, quick effect potassium, organic matter were 1.37 and 1.33,1.27 and 1.46,1.08 and 1.02,1.70 and 1.41 times compared to that of the control group respectively.(2) The assays of chitin and its derivatives against dry rot of potato tubers and plants were conducted, and the resistance related substances were determined. The results showed that: ① Chitosan and water-soluble chitosan can effectively inhibit dry rot of potato plants and stem with 84.6% and 89.7% potato tubers lesion diameter, respectively. ② It is demonstrated that chitosan and its derivatives can promote potato plants and tubers to produce enzymes and substances associated with disease resistance. On the third day after treatment, the activity of polyphenol oxidase (PPO) and phenylalnine ammonialyase (PAL) of 4.0 g/mL chitosan and water soluble chitosan experiment group were 1.40 and 1.30 times,1.49 and 1.61 times of the control group, while the total phenolic content were 1.14 and 1.20 times of the control group. The PPO activity of 4.0 g/kg chitosan and chitin treated were 15.6% and 25.6% higher than that of the control group, respectively.(3) When using 4.0 g/kg of chitin or chitosan as organic fertilizer to grow potatoes, the contents of dry matter, reduce sugar, starchp soluble protein in potato were 47.8% and 62.4%,8.3% and 16.7%,51.6% and 69.2%,24.8% and 44.2% higher than those of the control group, respectively.(4) To further explore the utilization of chitosan, pyridine chitosan was synthesized, characterized via molecular modification. Its antibacterial activity against Fulvia fulva, Botrytis cinerea and the effect of pyridine chitosan on the mycelium were studied. The results indicates that:① The MBC of chitosan and pyridine chitosan on against B. cinerea were 8.00 and 4.00 mg/mL, the MBC of chitosan and pyridine chitosan on against F.fulva were 2.00 and 1.00 mg/mL. From these data, it can be concluded that the antibacterial effect of pyridine chitosan is better than chitosan. ② Scanning electron microscopy exhibited that abnormally spherical or club-shaped cluster was observed on the end of the deformed and twisted hyphae. ③ It is noted that pyridine chitosan possessing efficient inhibition against bacteria and fungi is non-toxic through the cute toxicity tests in mice. |
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