engleski

A bet is open: Who would win a fight between phytophatogenic fungi and plant – growth – promoting - bacteria?

The increasing occurrence of extreme events has made climate change one of the most challenging problems in today's world with the great economic consequences for the fragile agricultural sector. The agricultural sector, and thus crop productivity, quality, and price stability, are threatened by warming temperatures, floods, intense heat, drought, wildfires, and storms. As a result, researchers and policy makers are focusing on developing novel approaches to adapt to a rapidly changing climate. In the project entitled "Potential of the rhizosphere microbiome in the adaptation of agriculture to climate change (PERSPIRE)", funded by the EU Regional Development Fund, we focused our research on the effects of flooding events (water retention after heavy rains) as a result of climate change on the development of plants and the response of their rhizospheric microbiome, to whose “health” plants are tightly dependent. The experiment was conducted in the controlled conditions (16 hours day/8 hours night ; 25 ˚C per day/20 ˚C per night ; 60-70% relative humidity), using cabbage (Brassica oleracea var. capitata f. alba) as a model plant. In the experiment plants were exposed to either one or two long-term floods (7 days duration of each flood) at different stages of development. At different time points (day 0, after flooding, and after the recovery period), all of the soil was removed from the pots, thoroughly mixed, and subsamples were collected for culture-based isolation and characterization of PGPB (plant growth-promoting bacteria). PGPB were isolated by inoculation on non-selective nutrient agar and incubation at 37o C (5 days). Approximately 20 morphologically distinct bacterial colonies were selected from each of the sampling points, purified and analyzed for various PGP characteristics using culturable methods on different selective media. 48 bacterial isolates (Bacillus, Pseudomonas, Stenotrophomonas, Peribacillus, Enterobacter etc.) exhibiting most PGP properties, were further selected for testing antagonistic/synergistic activity against mycelia of three selected phytopathogenic fungi (Fusarium oxysporum, Fusarium verticilloides and Sclerotinia sclerotiorum). Sequencing of 16S rRNA and ITS2 marker genes was used to determine identity of both bacteria and fungi used in the experiment. The bacterial suspension (adjusted to a concentration of 1.5 McFarland) was inoculated onto paper discs placed on the rim of the Petri dish containing potato dextrose agar. Bacterial cultures were grown for 72 hours, then a mycelial agar plug was added to the center of the agar plate and the plates were incubated at 25 °C for 5 days. Growth of both bacteria and mycelia was recorded each day. Different bacterial isolates showed variable percent inhibition of fungal mycelia. However, a total of six bacterial isolates isolated, exclusively from flooded samples showed strong antagonistic activity against mycelia. We believe these bacteria, adapted to flooding conditions, could be potential bioinoculums that could be used in the biocontrol of pathogenic fungi in crops affected by flooding as a consequence of climate change.

climate change ; floods ; PGPB ; phytophatogens ; fungi

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