Resistance response of Zantedeschia aethiopica and a colored Zantedeschia hybrid to a soft rot pathogen

Soft rot caused by Pectobacterium carotovora subsp. carotovora (PCC) is a serious disease in section Aestivae of the colored Zantedeschia. Zantedeschia aethiopica from section Zantedeschia has more resistance to PCC. To explore the resistance mechanisms in Zantedeschia spp., changes in resistance signal molecules (salicylic acid (SA), jasmonic acid (JA)) and antioxidant enzymes (polyphenol oxidase (PPO), peroxidase (POD)) were investigated in different resistant Zantedeschia species following elicitation with PCC. Resistant Z. aethiopica and susceptible Zantedeschia × elliottiana were chosen as experimental materials. The leaves of Zantedeschia plants were inoculated with a PCC suspension of 10⁶ CFU mL^-1 after artificial wounding. The content of SA and JA in leaves was detected by high-performance liquid chromatography (HPLC). The activities of PPO and POD were measured via colorimetric methods. The results showed that accumulation of SA in resistant Z. aethiopica increased significantly after infection by PCC, and the content was 2.64-6.35 times higher than in a susceptible colorful Zantedeschia hybrid; JA could not be detected in infected leaf samples, even though it could be detected after adding standard JA. Activities of PPO and POD increased in both the resistant Z. aethiopica and the susceptible colorful Zantedeschia hybrid, but activities in Z. aethiopica increased more quickly and obviously. The above results suggested that Zantedeschia depends on the defense mechanism of systemic acquired resistance to limit the soft rot pathogen, and the resistant Zantedeschia produced more phenols and quinones compounds to kill or inhibit PCC.