Suppression of Botrytis cinerea sporulation on irradiated grape leaf tissue by the antagonistic bacterium Serratia liquefaciens

A range of bacteria were screened to identify potential antagonists against Botrytis cinerea on grape tissue ( Vitis vinifera L.). From dual culture tests, 13 isolates were selected which exhibited antagonism towards B. cinerea mycelial growth. Inhibition zones ranged between 3 and 12 mm. These isolates were screened in a grape leaf bioassay. Irradiated leaf discs were inoculated with 5. cinerea (1 × 10 4 spores/ml) then challenged with bacteria applied at 1 × 10 8 colony forming units (cfu)/ml in tryptic soya broth (TSB). Sporulation of B. cinerea was significantly ( P = 0.05) reduced on leaf discs treated with Serratia liquefaciens isolates B47 and 171B by 62 and 57% respectively, 7 days after application. In a second leaf bioassay, B47 applied in TSB significantly ( P = 0.05) reduced B. cinerea sporulation by 65% after 21 days compared to a 39% suppression achieved with isolate 171B (applied in TSB) and the fungicide, iprodione. However, when applied in Ringers solution, both isolates failed to reduce B. cinerea sporulation. This research has identified two isolates of S. liquefaciens able to suppress sporulation of B. cinerea on grape tissue and has shown that bacterial application solution can strongly influence the degree of suppression achieved.