Page 233 - PC2019 Program & Proceedings

PLANT CANADA 2019

P39. Testing amendments and cover crops for improving soil health in vineyards
2
1
1
Christie, R. ; R. Honor ; L. Vasseur ; Guinel, F. 1
1 Wilfrid Laurier University
2 Brock University
With intensive agriculture, soils become impoverished because of nutrient depletion, structural changes,
and reduction in microbial diversity. Vineyards are especially prone to soil degradation due to the heavy
management required for effective yields. Using an operational vineyard in the Niagara Region, we tested
whether amendments in combination with cover crops would be efficient at restoring soil health. Plots
were exposed to one of the following treatments: an agromineral known as SRC, a synthetic fertilizer
(N/P/K, 20/20/20), or water only (control) with either ryegrass or a mix of forbs and legumes. Soil
properties, microbial abundance and respiration were measured. After two years, pH and microbial
abundance decreased in all treatments. Date of soil collection impacted the base saturation of cations,
especially that of Ca and K, which tended to decrease over the two-year period. The abundance of
nitrogen-fixers was influenced by soil sampling date and cover crop, and that of phosphate-solubilizers
was dependent on the soil sampling date + cover crop interaction. The microbial respiration varied
significantly between cover crop and soil collection date, with ryegrass soil amended with SRC having
the highest value at the end of the experiment. Although it is difficult to draw firm conclusions because of
the complexity of the interactions, the results obtained so far suggest that cover crops play an important
role in promoting vineyard soil health.

Frédérique Guinel (fguinel@wlu.ca)

P40. Strike against Pseudomonas syringae: rye cover crop promotes a shift in squash phyllosphere
bacterial abundance and plant gene expression
2
*1
2
2
Maglione, R. ; M. Ciotola ; M. Cadieux ; V. Toussaint ; M. Laforest ; S. Kembel
3
2
1 UQAM
2
Agriculture and Agrifood Canada
3 Université du Québec à Montréal (UQAM)
Pseudomonas syringae, is considered one of the most important bacterial plant pathogens. Soil
conservation practices, such as cover crops, are amongst tools that can contribute to reducing disease
pressure caused by bacteria. We have recently demonstrated that leaf surface (phyllosphere) bacterial
community structure changed when squash is grown with a rye cover crop treatment, followed by a
decrease of P.syringae symptoms. In this work, our goal was to describe the differential bacterial
abundance of the squash phyllosphere. We pursue the hypothesis that some abundant phyllosphere
bacteria could explain the decrease in P.syringae population. Thus, we grew squash, within a two-year
field, in four agricultural practices: bare soil, cover crops, chemically terminated cover crops and plastic
cover. We sampled squash leaves at 3 different dates. From samples wash, total DNA was extracted and
its 16S rDNA was sequenced and a bacterial bank was built with cultivable strains. With differential
expression analysis (DeSeq2, LeFSe) we pinpoint abundant phyllosphere bacteria, issued from the cover
crop treatment, belonging to Sphingomonas and Methylobacterium among others. Some of those bacteria
were found in the bacterial bank and our current work involved in competition validation assays on petri
dish against P.syringae population. We also measured gene expression from squash leaves. Plant
expression profiles display strong correlation with treatments. The exploration of marker genes related to
plant resistance is in progress.

Remi Maglione (remi.maglione@gmail.com)

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