Antioxidant Defense Strategies Against Diaporthe eres Infection in Hongyang Kiwifruit

Area of Science:

• Plant Pathology
• Biochemistry
• Postharvest Biology

Background:

• Diaporthe eres causes significant postharvest damage to kiwifruit (Actinidia chinensis).
• The antioxidant defense mechanisms of kiwifruit against this pathogen are not fully understood.

Purpose of the Study:

• To investigate the antioxidant defense strategies employed by kiwifruit during Diaporthe eres infection.
• To elucidate the dynamics of key antioxidant enzymes and their roles in disease progression.

Main Methods:

• Monitoring of pathogen development and tissue damage over time (0-4 days post-inoculation).
• Enzyme activity assays for superoxide dismutase (SOD) and peroxidase (POD).
• Bioinformatic analysis of peroxidase (POD) isoforms and gene expression.
• Quantification of malondialdehyde (MDA) as an indicator of membrane damage.

Main Results:

• A 3-day latent period preceded visible tissue breakdown and water-soaked lesions at 4 days post-inoculation.
• Superoxide dismutase (SOD) activity showed a biphasic pattern with peaks at 1 and 4 days post-inoculation, coordinated by mitochondrial gene CEY00_Acc02790.
• Peroxidase (POD) activity increased at 4 days post-inoculation; distinct POD isoforms were identified, with extracellular variants promoting cell wall reinforcement and intracellular variants mitigating reactive oxygen species (ROS) damage.
• Malondialdehyde (MDA) levels increased by 3 days post-inoculation, indicating membrane damage.

Conclusions:

• The study reveals a complex antioxidant response in the kiwifruit-Diaporthe pathosystem.
• The bimodal SOD activation and specialized POD functions are critical in the plant's defense.
• These findings offer targets for developing kiwifruit cultivars resistant to postharvest pathogens and for precision intervention strategies.