Evaluation of the strawberry epiphyte bacillus velezensis Hiii11 as a biological control agent of fungal pathogens in Arabidopsis thaliana.

HIRSCH MAILÉN; BURGES PABLO; MIGUELIZ LARA; VILLARREAL NATALIA; MARINA MARÍA

Chapadmalal

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiología General.; 2023

Sociedad Argentina de Microbiología General (SAMIGE).

The strawberry (Fragaria x ananassa Duch.) is susceptible to attack by fungal pathogenssuch as Botrytis cinerea and Rhizopus stolonifer. The biological control (BC) of plantdiseases has become relevant as an alternative to fungicides or other chemical substances.The BC consists of using living microorganisms capable of reducing or eliminatingphytopathogens or the disease caused by them, providing a benefit to the host plant. TheBacillus genus comprises several strains recognized as biological control agents (BCA). Weisolated the epiphyte HIII11 from strawberry leaves and identified it as Bacillus velezensis.Previously, we observed that B. velezensis HIII11 can inhibit B. cinerea in vitro growth. Inthe present work, we evaluated the in vitro inhibition of R. stolonifer through confrontationbetween HIII11 and the fungus and by the action of volatile compounds. In addition, westudied whether B. velezensis HIII11 exerts biocontrol of both pathogens in A. thaliana.Plants were inoculated with the epiphyte, and the control was mock-inoculated with MgCl210 mM. Then, four to five leaves per plant were inoculated with two drops of sporesuspension. We measured the infection area at 48 and 72 h post-inoculation (hpi). We alsodetermined the content of anthocyanins and phenolic compounds in plants previouslyinoculated with HIII11, and on control plants. The in vitro assays showed the inhibition of R.stolonifer by HIII11. The inhibition percentage was 40.6% when both microorganisms wereco-cultivated, and 10.2% when the inhibition by volatile compounds was evaluated. In thein vivo assays, we observed a significant fungal inhibition at 72 hpi for both pathogens.Interestingly, leaves were in healthier condition in plants previously inoculated with HIII11.In addition, by Tripan-Blue staining, we observed a lower amount of fungal mycelium in theinfected areas of inoculated leaves than the control ones (with pathogen but withoutbacteria). Finally, a significant increase in anthocyanins content in inoculated plants wasshown, although no differences were evident in the phenolic compounds content. Theidentification of BCA is complex and requires the evaluation of different aspects thatcomprise the BCA-plant-pathogen interaction. Along with previous data, these resultsprovide information about the role of B. velezensis HIII11 in A. thaliana as a BCA ofpathogens responsible for significant economic losses in strawberry cultivation andencourage us to continue studying the effects of HIII11 in strawberry plants and fruits.