Page 281 - PC2019 Program & Proceedings

PLANT CANADA 2019

P135. Modulation of lipopeptides production by Bacillus subtilis PTB185 in response to different
plant pathogens
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2
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2
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Cossus, L. ; F. Roux-Dalvai ; I. Kelly ; T. Nguyen ; H. Antoun ; A. Droit ; R. Tweddell
2
1 Laval university
2
Université Laval
Lipopeptides are essential compounds associated with the biocontrol activity of the Bacillus spp. In order
to better understand the biological mechanisms involved in the production of lipopeptides by Bacillus
subtilis strain PTB185, the bacterium was co-cultured on agar with one of the following plant pathogens:
Botrytis cinerea, Mucor sp., Pythium ultimum, Rhizoctonia solani, Sclerotinia sclerotiorum. After 5-7
days of growth, lipopeptides (surfactin, iturin, and fengycin) produced by PTB185 were extracted and
quantified using MALDI-TOF mass spectrometry. PTB185 was further cultivated in liquid media
supplemented with cell wall powder (1 g L ) of each tested pathogen. After 3 days of growth,
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lipopeptides were quantified in the culture filtrates and bacterial suspensions were tested in vitro for their
antagonistic activity against the plant pathogens. PTB185 inhibited on agar the growth of the pathogens
that were shown to strongly enhance the production of surfactin, iturin, and fengycin. In addition, the
incorporation of pathogen cell wall powders in the liquid medium was shown to stimulate the production
of iturin and fengycin and to improve the antagonistic activity of PTB185. This study indicates that
biological interactions stimulate the production of lipopeptides by B. subtilis. The results also suggest that
B. subtilis biocontrol activity could be strengthened by the composition of the medium.

Louis Cossus (louis.cossus@gmail.com)

TOPIC 15: Growth Regulators (Posters P136-P137)

P136. Karrikins: important regulators of seed germination in wildfire-prone regions
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2
Monthony, A. ; K. Baethke ; L. Erland ; S. Murch 2
2
1 University of Guelph
2 UBC
Wildfires are having devastating and regenerative impacts on the ecosystems of the Pacific Northwest.
We hypothesized that karrikins, a distinct class of plant growth regulators (PGRs) that are released from
burning plants during wildfires, induce seed germination in two ecologically important
species Balsamorhiza sagittata and Balsamorhiza deltoidea. B. sagittata grows in the dry ecosystems of
the Okanagan and B. deltoidea grows along the rain-drenched coast.To investigate our hypothesis, we
imbibed seeds in 0, 5 or 10 μM of gibberellic acid (GA), karrikin 1, 2 or 11 (KAR1, KAR2, KAR11) alone
and in combination. KAR2was more effective than KAR1or KAR11increasing seed germination in B.
sagittata by 3.35-fold (5 μM) and 5.4-fold (10 μM). 100% of viable B. deltoidea seeds germinated in
response to 10 μM KAR2.B. sagittata seedlings grown in axenic culture in a standard controlled
environment growth room entered a dormant phase at temperatures > 15°C and were recovered by
incubation in a refrigerated chamber at 3°C for 4-6 weeks. Thidiazuron (TDZ; 0 or 10 μM) induced de
novo regeneration. B. sagittata seedlings produced between 3-12 de novo shoots in response to 10 μM
TDZ. B deltoidea seedlings produced ≈66 (10 μM TDZ) regenerants resembling somatic embryos with
globular, heart shaped, torpedo and cotyledonary structures. Following a heat-stress experiment, 5
putatively temperature resistant germplasm lines of B. sagittata were recovered. Together, these studies
demonstrate that KAR2induces seed germination and providein vitromethods for conservation and mass-
propagation of Balsamorhiza species.

Adrian Monthony (monthona@uoguelph.ca)

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