Potassium influenced phenylalanine ammonia-lyase, peroxidases and polyphenol oxidases in Fusarium graminearum infected maize (Zea mays L.)
Potassium (K) fertilizer is important for the reduction of many plant diseases, e.g., stalk rot of maize (Zea mays L.). However, the mechanism by which potassium promotes resistance to pathogens is not completely understood. Fusarium graminearum, which is the main pathogen causing stalk rot in maize, was selected to study the effect of potassium on phenylalanine ammonia-lyase (PAL; EC 184.108.40.206), peroxidase (POD; EC 220.127.116.11) and polyphenol oxidase (PPO; EC 18.104.22.168), at both the physiological and molecular level. Gene expression was quantified by real-time reverse transcription PCR (Q-RT-PCR) technology. The incidence of maize stalk rot was significantly reduced by K application. After inoculation with F. graminearum, the potassium concentration increased in susceptible organs. Potassium induced the expression of and sustained elevated activities of PAL, POD, and PPO when maize was inoculated with the pathogen. The expression of the corresponding genes was also stimulated by potassium. This study demonstrated that potassium addition enhanced maize resistance to stalk rot by activating the expression and activity of defense-related enzymes involved in phenol metabolism.