BIOCONTROL OF SCLEROTINIA WILT OF SUNFLOWER BY PSEUDOMONAS-FLUORESCENS AND PSEUDOMONAS-PUTIDA STRAINS

An increase in early injury to the roots and collar of sunflower plant s caused by Sclerotinia sclerotiorum has been observed in France for s everal years. In vitro tests (inhibition of fungi and cyanide producti on by bacterial strains) and in situ tests (in nonsterile humus, in a growth chamber) were performed to screen the most efficient Pseudomona s fluorescens and Pseudomonas putida strains effective against this fo rm of injury caused by S. sclerotiorum. Although there was no correlat ion between in vitro and in situ tests, a positive correlation between in situ tests and field experiments was obtained. At least 1 x 10(6) bacteria per seed were required for significant protection in in situ tests and field trials demonstrated that significant protection of sun flower was obtained by seed bacterization with selections of P. fluore scens and P. putida.