Inhibitory effect of lactoferrin against gray mould on tomato plants caused by Botrytis cinerea and possible mechanisms of action

Lactoferrin (LF), an 80 kDa iron binding glycoprotein, was effective in the control of gray mould caused by Botrytis cinerea on tomato. LF strongly inhibited spore germination and germ tube elongation of B. cinerea in vitro, especially at 100 mg/L. When viewed by fluorescence microscopy following staining with propidium iodide, the membrane integrity of B. cinerea conidia treated with LF (50 mg/L) decreased to 68% at 2 h. The leakage of carbohydrate and protein from mycelia increased as the dose of LF increased compared with the untreated controls. Furthermore, methane dicarboxylic aldehyde (MDA) content in B. cinerea spores exposed to LF increased markedly. The activities of superoxide dismutase and catalase in spores treated with LF were also 1.3, twice as high as those in the control at 6 h, whereas ATP content was 1.5 times lower. In planta assays demonstrated that LF exhibited significant curative effect (76.3%, 100 mg/L) against gray mould, compared with the preventive effect (52.6%, 100 mg/L). The mechanisms by which LF decreased gray mould decay of tomato plant may be directly related to the severe damage to the conidia plasma membrane and loss of cytoplasmic materials from the hyphae. These findings suggest that LF has potential as an antifungal agent to reduce the severity of gray mould of tomato plants.