Suppression of Strawberry Black Root Rot Disease in the Field by Chitosan Applied as Root Dipping and Foliar Spray

Abstract

Eight concentrations, i.e., 0.0, 0.5,1,2,3,4,5 and 6 g/L of chitosan were tested to study their effect on linear growth of strawberry black root rot fungi (F. solani, R. solani and M.phaseolina) in the laboratory. Results revealed that all tested concentrations of chitosan except that 0.5 and 1 g/L significantly reduced the linear growth of all tested fungi. Complete reduction was obtained with chitosan at 6 g/L for all tested fungi. The highest reduction was obtained with chitosan at 5g/L which reduced the linear growth by 91.1, 90.3 and 88.9 % for F. solani, R. solani and M.phaseolina respectively. In field experiments, application of chitosan at concentrations of 5 & 6 g/L and at 0.5 &1g/L as root dipping and foliar spray respectively were evaluated alone or in combination to study their effect on black root rot disease, some vegetative characters, yield and enzyme activities of strawberry plants. Results revealed that all tested concentrations of chitosan applied as root dipping or foliar spray significantly reduced the black root rot disease of strawberry plants. The most effective treatments are combined treatments between root dipping and foliar spray which reduced disease incidence and severity more than 76.8 and 75.9 % respectively. Followed by root dipping treatment which reduced disease incidence and severity more than 64.3 and 61.1 % respectively. While, foliar spray was less effective. The highest increase of fresh and dry weight was obtained with combined treatments between root dipping and foliar spray which increased the fresh and dry weight more than 85.7 and 89.5 % respectively. While, single treatments showed moderate effect. Moreover, all tested concentrations of chitosan applied as root dipping or foliar
spray significantly increased the strawberry yield. The most effective treatments are combined treatments between root dipping and foliar spray which increased the yield 92.0 %. Followed by root dipping treatment which increased the yield more than 58.0 %. While, foliar spray was less effective. Furthermore, combined treatments between root dipping and foliar spray caused increased the peroxidase and chitinase activities more than 172.0 and 181.3 % respectively. While, single treatments showed moderate effect.