Bacillus subtilis LBF02 as Biocontrol Agent Against Leaf Spot Diseases Caused by Cercospora lactucae-sativae in Lettuce

Abstract

More than 51 isolates of bacteria were obtained from leaves, crushed leaves and rhizosphere of lettuce plants. The bacteria isolates were purified and assayed against Cercospora lactucae-sativae on PDA plate by dual culture technique. Four isolates showed zone of inhibition against the pathogens. The antagonistic bacteria isolate LBF02 showed the highest percentage of growth inhibits against C. lactucae-sativae leaf spots with 80.82% inhibition, compared with the control. Based on morphological and biochemical tests, isolate LBF02 was identified as belonging to the Bacillus subtilis group. The LBF02 isolate was chosen for the formulation development. The formulation contained 40 ml of cell suspension, 89 g of rice flour, 1 ml of vegetable oil and 10 g of sucrose. The biocontrol of leaf spot diseases was tested by using a formulation applied in greenhouse experiments. The result showed that spraying 1 hour before or after the pathogen inoculation on lettuce plants was more effective in suppressing leaf spot disease than simply pathogen inoculation alone. Moreover, the antagonistic bacteria in formulation have the ability to survive for more than 6 months under storage at room temperature and survive for up to 15 days on lettuce leaves.

Trichoderma asperellum (NST-009): A potential native antagonistic fungus to control Cercospora leaf spot and promote the growth of 'Green Oak' lettuce (Lactuca sativa L.) cultivated in the commercial NFT hydroponic system

“…and vitamins A, C, and K (Camejo et al 2020). However, the leaf spot disease caused by Cercospora lactucae-sativae is one of the most significant problems in the production of 'Green Oak' leaf lettuce, which affects both the quantity and quality of the product (Srimai & Akarapisarn 2014;Khamun et al 2017). The disease occurs on the lower older leaves and spreads to the younger ones.…”