Chemically Modified Chitosans as Antimicrobial Agents against Some Plant Pathogenic Bacteria and Fungi

Rabea E.I., Steurbaut W. (2010): Chemically modified chitosans as antimicrobial agents against some plant pathogenic bacteria and fungi. Plant Protect. Sci., 46: 149–158. The antimicrobial activity of eight chemically modified chitosans against plant pathogenic bacteria of crown gall disease agrobacterium tumefaciens and soft mould disease Erwinia carotovora and fungi of early blight disease alternaria alternata, root rot disease Fusarium oxysporum, and damping off disease Pythium debaryanum was investigated. The minimum inhibitory concentration (MIC) of these compounds against the tested bacteria showed that N-(o,o-dichlorobenzyl)chitosan exhibited a high activity against a. tumefaciens and E. carotovora (MIC = 500 and 480 mg/l, respectively). In addition, the antifungal behaviour was investigated in vitro on mycelial growth and spore germination. N-(p-fluorobenzyl)chitosan was the most active against the mycelial growth of a. alternata with an EC50 of 703.4 mg/l, while the N-(o-chloro,o-fluorobenzyl)chitosan exhibited a high activity against F. oxysporum and P. debaryanum (EC50 = 641.2 and 155.7 mg/l, respectively). Against the fungal spore germination, all modified chitosans showed a higher inhibition of spore germination than unmodified chitosan. The compound of N-(o,o-di fluorobenzyl)chitosan exhibited a high inhibition percentage against a. alternata. However, N-(o-chlorobenzyl)chitosan and N-(p-chlorobenzyl)chitosan were significantly highly active against the spore germination of F. oxysporum.