Reproducing Botryosphaeria Dieback Foliar Symptoms in a Simple Model System

Area of Science:

• Plant Pathology
• Mycology
• Viticulture

Background:

• Botryosphaeria dieback is a significant grapevine trunk disease globally.
• It is caused by various Botryosphaeriaceae species, including Diplodia seriata and Neofusicoccum parvum.
• These fungi induce wood lesions, affect leaves and berries, and can lead to plant death.

Purpose of the Study:

• To establish a simple model system for reproducing foliar symptoms of Botryosphaeria dieback.
• To better characterize fungal pathogenicity of Diplodia seriata and Neofusicoccum parvum isolates.
• To investigate the mechanisms underlying symptom development in grapevines.

Main Methods:

• Green stems of 'Aragonez' grapevine cuttings were inoculated with five different fungal isolates (3 N. parvum, 2 D. seriata).
• Experiments were conducted over four years (2011-2014) to ensure reproducibility.
• Lesion development, foliar symptom incidence, and molecular responses (gene expression, phenolic accumulation) were monitored.

Main Results:

• Neofusicoccum parvum caused larger lesions compared to Diplodia seriata three months post-inoculation.
• A higher percentage of plants exhibited foliar symptoms under N. parvum treatments eight months post-inoculation.
• Plant stress responses included downregulation of superoxide dismutase (SOD) and fasciclin-like arabinogalactan protein (fascAGP), and upregulation of stilbene synthase (STS) genes, alongside phenolic accumulation.

Conclusions:

• The developed model system effectively characterized isolate pathogenicity and correlated it with Botryosphaeria dieback foliar symptoms.
• Key molecular changes, including SOD, fascAGP, and STS gene modulation, are linked to symptom development.
• This research provides insights into the pathogenesis of Botryosphaeria dieback in grapevines.