Biocontrol of Sclerotinia wilt of sunflower by Pseudomonas fluorescens and Pseudomonas putida strains

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Abstract
An increase in early injury to the roots and collar of sunflower plants caused by Sclerotinia sclerotiorum has been observed in France for several years. In vitro tests (inhibition of fungi and cyanide production by bacterial strains) and in situ tests (in nonsterile humus, in a growth chamber) were performed to screen the most efficient Pseudomonas fluorescens and Pseudomonas putida strains effective against this form of injury caused by S. sclerotiorum. Although there was no correlation between in vitro and in situ tests, a positive correlation between in situ tests and field experiments was obtained. At least 1 × 106 bacteria per seed were required for significant protection in in situ tests and field trials demonstrated that significant protection of sunflower was obtained by seed bacterization with selections of P. fluorescens and P. putida.Key words: biological control, Pseudomonas fluorescens, Pseudomonas putida, Sclerotinia sclerotiorum, sunflower, bacterization.