Effect of root-knot nematode inoculation on rhizospheric soil pH and microbial community of cucumber (Cucumis sativus L. ) plant

Root-knot nematodes (RKNs) are the most destructive field pathogens of cucumber plant. This study evaluated rhizospheric soil pH and soil microbial community response to RKN inoculation. Results of the study show that aerobic bacteria, anaerobic bacteria and total bacteria number as well as bacteria/fungi (B/F) ratio gradually decline with the increasing inoculation rate. However, fungi number gradually increases with increasing inoculation rate. Both actinomyce/fungi (A/F) ratio and actinomyce number increase at an inoculation rate of 2 000 eggs per plant, but gradually decrease with increasing inoculation rate. Under RNKs inoculation, rhizospheric soil pH is significantly positively correlated with aerobic bacteria, B/F, anaerobic bacteria number, total bacteria number, actinomyce number and A/F ratio. However, rhizospheric soil pH is significantly negatively correlated with fungi number. RKNs infection apparently increases fungal population density in rhizospheric soils, implying degradation of soil quality due to RKNs infection.