Determination of antagonistic potential of endophytic bacteria isolated from lettuce against lettuce white mould disease caused by Sclerotinia sclerotiorum

In this study, biocontrol efficiency of endophytic bacterial isolates obtained from the leaf lettuce (Lactuca sativa L.) healthy plants was investigated against white mould disease agent Sclerotinia sclerotiorum in vitro and in vivo conditions. Antagonistic efficiency of endophytic bacterial isolates was determined to inhibit mycelial growth and sclerotial germination, suppress disease incidence caused by S. sclerotiorum. A total of 48 endophytic bacterial isolates were isolated from different tissues of lettuce healthy plants. Mycelial growth and germination of sclerotia of S. sclerotiorum in vitro inhibited 18 bacterial isolates. Bacillus subtilis and B. amyloliquefaciens isolates were found to be the most efficient ones, which significantly inhibited the mycelial growth by 68.1–83.1%, germination of sclerotia by 82.7–89.6% and suppressed disease incidence by 55.7–75% caused by S. sclerotiorum. In addition, the fungal mycelium close to the inhibition zone in dual culture was denser and darker in colour. B. subtilis and B. amyloliquefaciens isolates caused significant morphological alterations in hyphae such as hyphal shrivelling and perforation close to the inhibition zone in dual culture. Significant suppression in the mycelial growth, sclerotial germination and disease incidence caused by endophytic bacterial isolates indicate that isolates of B. subtilis and B. amyloliquefaciens could be considered as possible biocontrol agents against soil-borne fungal diseases.