| Summary: | This work highlights the ability of various cyanobacterial
extracts from Anabaena spp., Tolypothrix spp., Nostoc or
Trichormus, among others genera, to control the incidence of
damping-off caused by Pythium ultimum in cucumber seedlings.
Protocols applied aimed at the preliminary characterization of the
cyanobacterial collection were very useful for predicting their
phytotoxic, phytostimulating and biopesticidal capacity. First, the
phytostimulatory or phytotoxic potential of a collection of 31
sonicated cyanobacterial extracts was analyzed by calculating
the germination index in watercress seeds and the increase or
loss of seedling weight. Likewise, the collection was
characterized according to its ability to inhibit the growth of P.
ultimum by dual culture bioassays and detached-leaf test.
Finally, after selecting the most effective extracts, a preventive
damping-off bioassay was performed based on cucumber seed
biopriming. The strain SAB-M465 showed to be the most efficient
strain against the in vitro growth of P. ultimum, while SAB-B912
was more discreet in this regard, but proved to be the most
effective as a germination stimulator. Seed biopriming strategy
with sonicated extracts of cyanobacteria revealed a remarkable
promoter effect in the early stages of plant development,
although only SAB-M465 was positioned as an effective control
agent against damping-off caused by P. ultimum in cucumber
seedbeds.
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