To investigate the key role of endophytic fungi in maintaining host adaptability and overall health, endophytic fungi were isolated from healthy root, stem and leaf tissues of Impatiens hawkeri, and the dominant strain FG8 with growth-promoting and antagonistic functions was screened. Strain FG8 was identified as Thelonectria veuillotiana by morphological and molecular biological methods. It exhibited an antifungal rate of 58.57% against Stagonosporopsis cucurbitacearum, the pathogen causing leaf spot disease of I. hawkeri. The broad-spectrum antifungal activity was verified by the plate confrontation method, and FG8 showed inhibitory effects on six common pathogenic fungi, with the highest inhibition rate of 64.5% against Apiospora intestini. Furthermore, strain FG8 displayed remarkable growth-promoting and antagonistic characteristics: it produced indole-3-acetic acid at 12.74 μg/mL, and possessed the abilities of phosphate solubilization, potassium mobilization, nitrogen fixation and siderophore synthesis. Its antagonistic activity was mediated by β-glucanase, amylase, cellulase and pectinase. Meanwhile, FG8 significantly induced the activities of four defensive enzymes in I. hawkeri, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and polyphenol oxidase (PPO). Seed growth-promotion experiments demonstrated that the root length, plant height, fresh weight and dry weight of seedlings in the FG8-treated group were significantly higher than those in the control group. These results indicate that strain FG8 has both growth-promoting and biological control functions, which can provide a potential resource for the biological control of I. hawkeri leaf spot and the development of fungal fertilizers. Its field application effect and mechanism of action need to be further explored.
Li et al. (Wed,) studied this question.