Development of Screening Technique

Goal – Develop a rapid and reliable screening technique for resistant grape germplasm.

Activities – Compared screening methods for resistance to Eutypa dieback among nine genetically-diverse cultivars.

3.1

Results & Outputs
Merlot and Primitivo were most resistant to Eutypa dieback, based on both methods (hardwood cuttings and detached canes). However, the detached-cane method – a rapid alternative that takes only 5 weeks – differentiated cultivars similarly to the hardwood-cutting method, which is the standard in most labs.

The susceptible control, table-grape cultivar Thompson seedless, was ‘beat’ by an even more susceptible table grape cultivar, Husseine. Fortunately, this is not a commercial table grape, but it can serve as a new susceptible control in our studies.

Significant Outcomes & Impacts
The detached-cane method will serve as a phenotyping assay for use with materials from VitisGen and other grape breeding projects. In this way, our SCRI project builds on other SCRI projects that have already completed major genotyping efforts.

Develop a detection tool for the early stage of infection

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.

1.3b

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
by HRCT.
For more movies, please click the link below:
http://www.youtube.com/channel/UC7YEU_hMmKB9IEsoAUkbljg/feed

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.
1.4
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.

Develop a detection tool for spores of wood-canker 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.

1.1

 

Results & Outputs – Demonstrated that both young and mature vineyards are at similar risk of infection by spores of the same trunk pathogens.

1.2

 

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.