Effect of depolymerization degree of the natural biopolymer chitosan on some plant pathogenic bacteria and fungi | ||
| Journal of Pest Control and Environmental Sciences | ||
| Volume 15, Issue 1, June 2007, Pages 69-85 PDF (242.46 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jpces.2007.459649 | ||
| Author | ||
| Mohamed E. I. Badawy* | ||
| Department of Pesticide Chemistry, Faculty of Agriculture, 21545-El-Shatby, Alexandria University, Alexandria, Egypt. E-mail: m_eltaher@yahoo.com | ||
| Abstract | ||
| Three different molecular weights of chitosans were obtained from a commercial sample of chitosan by a method based on nitrous acid depolymerization. Molecular weights of chitosan samples were determined by measurements of intrinsic viscosity that were 0.5×104, 3.7×104 and 5.7×104 Dalton for the prepared compounds and 2.9×105 Dalton for the native chitosan sample. The effect of antimicrobial activities of these compounds against some economic plant pathogenic bacteria and fungi was investigated. The antibacterial assessment of the chitosan compounds was performed with Nutrient Agar dilution method against the bacteria cultures of crown gall disease (Agrobacterium tumefaciens) and soft mould disease (Erwinia carotovora) and the results are expressed as Minimum Inhibitory Concentration (MIC). In general, E. carotovora is more sensitive to these compounds than A. tumefaciens. The result also indicated that chitosan with a molecular weight of 0.5×104 Dalton exhibited a good antibacterial potency against A. tumefaciens with MIC = 2600 mg.L-1 while chitosan with a molecular weight of 3.7×104 Dalton is the most active one against E. carotovora with MIC = 950 mg.L-1. The antifungal assessment against the leaf spot and blight (Alternaria alternata), the grey mould (Botrytis fabae), the root rot disease (Fusarium oxysporum) and the black mould (Rhizopus stolonifer) was achieved using the mycelial radial growth inhibition technique and the results are expressed as Minimum Effective Concentration of 50% of mycelia growth (EC50). Generally, the result demonstrated that the antifungal activity was increased with the decreasing of the molecular weight and a chitosan low molecular weight (0.5×104 Dalton) was exhibited a high antifungal potency against B. | ||
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