Abstract:

Laboratory experiment and pot experiment were conducted to investigate effects of cinnamic acid treatments on seed germination，seedling growth，mycelia growth of Fusarium oxysporum f. fabae，occurrence of faba bean Fusarium wilt，rhizosphere microbial activity，diversity and community of faba bean. The results showed that seed germination and seedling growth were inhibited by cinnamic acid treatments，the higher the concentration，the stronger the inhibitory impacts. The most remarkable inhibitory impacts were observed on leaf number and root weight by cinnamic acid treatments. Mycelia growths of Fusarium oxysporum f. fabae were significantly promoted by cinnamic acid at low concentration and inhibited at high concentration. Disease index of faba bean fusarium wilt，amount of Fusarium oxysporum significantly increased and microbial activity（AWCD value），Shannon diversity index and substrate richness decreased with 100 and 200 mg · L^-1 cinnamic acid treatments. Principal component analysis demonstrated that cinnamic acid treatment changed the rhizospheric microbial community composition obviously，and the carbohydrates，carboxylic acids，and amino acids are sensitive carbon sources for differentiating the changes of microbial community induced by cinnamic acid. Cinnamic acid reduced rhizosphere microbial diversity，promoted the pathogen infection of faba bean and increased the infection of Fusarium wilt of faba bean. Cinnamic acid is an autotoxin in the continuous cropping obstacle of faba bean.

Key words: faba bean, cinnamic acid, Fusarium wilt, rhizosphere microbial functional diversity