Page 17 - CSHS 2022 Book of Abstracts - 2022-08-22 web version

CSHS 2022 Conference

Abstracts – Poster Presentations

(CP.1) Quantification of Ilyonectria mors-panacis in ginseng garden soil using droplet digital and
quantitative PCR
Komathy Prapagar , Sean Westerveld , Amy Shi , Mary Ruth McDonald , Melanie Kalischuk
2
1*
1
3
1
1. Department of Plant Agriculture, University of Guelph, Guelph, ON; 2. Ontario Ministry of Agriculture, Food and Rural
Affairs, Simcoe, ON; 3. Ontario Ginseng Growers Association, Simcoe, ON
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American Ginseng (Panax quinquefolius L.) is an economically valuable medicinal crop grown in North America but
cultivation is impacted by replant disease involving Ilyonectria mors-panacis (IMP). A primer set was developed to a
genomic region of IMP and tested for sensitivity and specificity in quantitative PCR (qPCR). The qPCR assay was
sensitive and detected 0.59 pg of total DNA extracted from a pure IMP culture. The assay was specific for IMP and
did not cross-react with other common soil-borne microbes including Fusarium, Verticillium, Pythium and
Phytophthora. To test the performance of the assay under ginseng production field conditions, the qPCR assay was
used to quantify IMP in a fumigation trial arranged in a randomized complete block design. Visual observations of
replant disease correlated with the IMP DNA copy number estimated using the qPCR assay. The chloropicrin
fumigated areas had 2.1 x 104 +/- 2.33 IMP DNA copy number and were significantly lower than 140 x 104 +/-55.91
IMP DNA copy number for the untreated control. To examine the IMP detection assay further, the primers were
tested in droplet digital PCR (ddPCR). Both qPCR and ddPCR detection provided similar results in the quantification
of IMP with respect to the different fumigation treatments with a Pearson correlation coefficient of r= 0.94. To
quantify IMP in soil samples, ddPCR was more sensitive than qPCR but due to the high cost associated with
equipment for ddPCR, the qPCR detection method may be the most preferred method for routine quantification of
IMP in soil samples.

(CP.2) Optimizing boron delivery in subirrigated pot chrysanthemums
Katherine R. Teeter-Wood*, Edward J. Flaherty, Alyna J. Donetz, Gordon Hoover, Barry J. Shelp
Department of Plant Agriculture, University of Guelph, Guelph, ON
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Greenhouse floriculture operations must produce high-yielding quality flowers in a manner that poses little
environmental risk. Unfortunately, excess boron (B) levels have been detected in southern Ontario waterways near
greenhouse operations. Closed subirrigation systems can minimize this contamination by recycling nutrients.
Current fertilizer recommendations are based on overhead watering, rather than subirrigation. Therefore, we
hypothesized that B delivery to modern cultivars of subirrigated chrysanthemum can be optimized, compared to
industry standards, while generating plants of similar yield and quality. My objective was to reduce the supply of B
during vegetative growth, followed by the removal of the nutrient suite at bud break, without negatively affecting
plant and flower quality. Two experiments were conducted in a naturally-lit greenhouse using a randomized
complete block split-plot design with four blocks. Nutrient treatment was considered as the main plot and cultivar
as the sub-plot. The first experiment supplied 5.00-1.25 μmol L-1 B (100-25% of current industry standards) and
the second experiment supplied 1.25-0.31 μmol L-1 B (25-6.25%) during vegetative growth, and water only during
reproductive growth. No difference in plant or flower fresh/dry mass yields, flower development, or visible
symptoms of nutrient deficiency were found with 5.00-1.25 μmol L-1 B; this was accompanied by sufficient tissue-B
levels in recently matured leaves at bud emergence. However, deformed reproductive structures and inadequate
tissue-B levels were found with 0.63-0.31 μmol L-1 B, indicating that B was in short supply. This research will
contribute to the development of a sustainable low-input nutrient delivery strategy for floricultural operations.

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