Isolation and identification of ginger Fusarium wilt pathogen and the effect of spore suspension concentration on the extent of disease

A pathogenetic fungus strain was isolated from the diseased ginger in Pingdu,Shandong Province,which was identified as Fusarium oxysporum f. sp. zingiberi by morphological identification,rDNA-ITS sequence analysis and inoculation experiment. Spores of the strain were inoculated into healthy soils in pot at different concentration levels to study the effect of different inoculation spore suspension of pathogen on ginger Fusarium wilt. Results showed a close relationship between the concentration of inocula in soil and the disease incidence rate of ginger Fusarium wilt. The minimal concentration that induced the ginger Fusarium wilt was 103per gram soil,and the disease incidence increased with the increase of inocula concentration in soil. Until the inocula concentration attained a certain level(105),the disease incidence would no longer increase. The spore suspension concentration inoculated was found to have a significant influence on the abundance of pathogen in rhizosphere and bulk soil of the ginger plants. The abundance of pathogen in rhizosphere soil was 1. 19 to 1. 86 times higher than those in bulk soil in different treatments. It was concluded that whether the ginger Fusarium wilt occurred or not was related to the abundance of pathogen in both rhizosphere and bulk soil,while the disease incidence was mainly determined by the number of the pathogen in plant rhizosphere soil.