BIOCONTROL OF FUSARIUM-WILT OF RADISH IN COMMERCIAL GREENHOUSE TRIALS BY SEED TREATMENT WITH PSEUDOMONAS-FLUORESCENS WCS374

In 1989, research was initiated on biological control of Fusarium wilt of radish by the plant growth-promoting rhizobacterium strain, Pseudomonas fluorescens WCS374, in a commercial greenhouse. During 4 consecutive years, radish seeds with one of three treatments were drilled into naturally infested greenhouse soil for a number of successive crops of radish. The three seed treatments were control, film-coating control, and film-coating with bacteria. At harvest time of each successive crop of radish, the disease incidence, yield, and root colonization by the applied strain were monitored in 16 fixed plots (0.5 m(2)) per treatment. In six out of 11 crops of radish, P. fluorescens WCS374 significantly (P less than or equal to 0.05) suppressed Fusarium wilt disease, compared with the film-coating control. The relative reduction of disease by the bacterial treatment compared with the film-coating control treatment ranged from 18.6 to 68.3%, with an average of 42.6%, whereas the relative increase of yield ranged from 19.5 to 100.1%, with an average of 44.7%.