Role of Chitosan in Disease Suppression, Growth and Yield of Carrot

Abstract

An attempt was made for controlling of Rhizoctonia canker caused by Rhizoctonia solani and southern blight caused by Sclerotium rolfsii in pot and field experiments under inoculated condition and also to increase the growth promoting factors and yield of carrot through the application of chitosan. Before setting the experiments in the field, laboratory experiments were carried out to select virulent isolates of R. solani and S. rolfsii and effective dose of chitosan on mycelial growth inhibition of virulent isolates of test pathogens. In the pathogenicity test, R. solani isolate R-1 and S. rolfsii isolate S-1 were found to be the most virulent against carrot seedlings. In vitro application of 1.0% chitosan was found to inhibit 100% mycelial growth of both tested pathogens. The field experiment was laid out following randomized complete block design with four treatments, where no treatment was done in T₁, pathogen was inoculated in T₂ and seed treatment and soil amendment with 1.0% chitosan was done in T₃ and T₄, respectively, in pathogen inoculated condition. Application of 1.0% chitosan as seed treatment or soil amendment significantly reduced post-emergence seedling mortality, incidence of diseases and enhanced seedling growth and also yields of carrot. On the contrary, post-emergence seedling mortality, incidence of Rhizoctonia canker and southern blight of carrot were highest in treatment T₂ where soil was inoculated with pathogens. Chitosan could be used as an alternative of fungicide to suppress Rhizoctonia canker and southern blight in sustainable agriculture and improvement the yield of carrot.