Our goal is to develop a new method to detect trunk diseases by sampling asymptomatic leaves. We revealed a unique set of grape genes expressed in asymptomatic leaves in the early phase of infection, using Botryosphaeria dieback pathogen Neofusicoccum parvum as a model to study host responses to a trunk pathogen. Tests are in progress to confirm specificity of these grape genes to Neofusicoccum infection, in inoculations with other trunk pathogens, common foliar pathogens, and to rule out possible interactions with drought stress.
Link to presentation:Early Detection
Goal– To determine if water stress exacerbates infection and test specificity of host-based markers to infection
Activities – Identification of host-based markers specific to infection and water stress
Two watering regimes tested:
- Well-watered control
- Severe water stress (16-17 bars leaf water potential)
Three inoculation regimes tested:
- NINW: non-inoculated non-wounded
- NIW: non-inoculated wounded
- IW: inoculated wounded
Results & Outputs – To understand how abiotic stress can influence disease progression and to validate molecular marker specificity to Neofusicoccumparvum.
Goal 2 – Accurate identification of trunk fungi
Activities – Allow for proper disease management and control practices
Results & Outputs – Developed a comprehensive DNA sequence database of trunk inhabiting fungi
Significant Outcomes & Impacts – Accurate species identification will lead to proper disease management practices.
Goal – Develop a detection tool for the early stage of infection, to quickly identify infected nursery stock, and as a study tool for field-testing new pruning-wound protectants.
Activities – Defined the timing and characteristics of the early stage of infection by the Botryosphaeria dieback pathogen Neofusicoccum parvum, based on spread of the infection and anatomic changes in the trunk, and differential gene expression in the leaves.
Use of High Resolution Computed Tomography
HRCT of grapevine at 2weeks after infection
HRCT of uninfected grapevine
Our focus in 2013-2014 was on Neofusicoccum parvum, which attacks grape, almond,
and pistachio. As the canker developed, anatomical responses in the woody stems of
potted grapes were examined by light microscopy and High Resolution Computed
Tomography (HRCT). Comparisons of inoculated – wounded plants (IW) vs. non-
inoculated – wounded plants (NIW) showed the main differences at 2 MPI. IW plants
were characterized by xylem vessels filled with gels, in stems of intact plants examined
For more movies, please click the link below:
Results & Outputs – Identified a set of eight grapevine genes (aka ‘molecular signature’) expressed in leaves during the early stage of infection from 0.5 to 1.5 months post-inoculation (MPI). For e.g., genes VIT_00s1455g00010 (dark bars) and VIT_01s0026g02710 (white bars) are highly expressed in inoculated plants, compared to the non-inoculated control plants.
Significant Outcomes & Impacts – Demonstrated ‘Proof of concept’, that the early stage of infection in the stem is detectable in asymptomatic leaves. This was first in a series of experiments, the next of which will confirm specificity of the molecular signature for possible interactive effects with drought stress and other trunk pathogens.
Goal 1 – Develop a detection tool for spores of wood-canker pathogens (aka trunk pathogens), combined with new molecular markers for rapid identification.
Activities – Evaluated spore traps in young, apparently-healthy vineyards vs. mature, diseased vineyards.
Results & Outputs – Demonstrated that both young and mature vineyards are at similar risk of infection by spores of the same trunk pathogens.
Significant Outcomes & Impacts – Growers routinely forego preventative practices in young vineyards because trunk diseases are not a serious problem until year 8. Our results make it clear – disease prevention should be adopted in young vineyards.