Abstract
White rust caused by Puccinia horiana is a destructive disease of chrysanthemum plants. To better understand the resistance mechanisms of composite species to this disease, the leaf cuticular traits, antioxidant and defensive enzymes activities of immune (Chrysanthemum makinoi var. wakasaense) and highly susceptible (Ajania shiwogiku var. kinokuniense) species were compared. Trichome density of two species was markedly different, negatively associated with plant resistance to P. horiana. Total wax load in C. makinoi var. wakasaense was two times more than that in A. shiwogiku var. kinokuniense. The wax composition in immune one was abundant in esters and primary alcohols. Superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7), polyphenoloxidase (PPO, EC 1.14.18.1 or EC 1.10.3.2) and phenylalanine ammonia lyase (PAL, EC 4.3.1.5) activities were investigated. In C. makinoi var. wakasaense, the activity of SOD and POD increased rapidly after inoculation, which might be non-host induced reactive oxygen species (ROS) activated antioxidant enzymes, however SOD and POD remained a low and steady level in the highly susceptible one after inoculation. Quick increase in PPO activities after inoculation was observed in both species, however it remained higher in C. makinoi var. wakasaense at the late period of inoculation. PAL in C. makinoi var. wakasaense was induced after pathogen inoculation, but not in A. shiwogiku var. kinokuniense, suggesting that these two enzymes might contribute to the resistance to P. horiana.
