2019 Colombo PeerJ
Evaluation of in vitro methods to select effective streptomycetes against toxigenic fusaria
Colombo EM, Pizzatti C, Kunova A, Gardana C, Saracchi M, Cortesi P, Pasquali M.
Fusarium spp. affect yield quantity and quality of wheat and barley and contaminate the harvested grains with mycotoxins. The efforts aimed at helping growers to reach an integrated pest management lead scientific research to evaluate novel biocontrol agents against plant pathogens, also as a consequence of the restrictions in the use of chemicals for crop protection due to the latest European laws.
Therefore, within a PhD project focused on the evaluation of novel biocontrol bacteria belonging to the Streptomyces genus, several factors have been assessed in order to understand their effect on a common screening procedure adopted in laboratory to identify microorganisms able to reduce disease severity in planta.
Culture medium (N=6) and Fusarium strain diversity (N=5) have been tested in dual culture (a common procedure adopted to select microorganisms able to inhibit fungal development) to evaluate their effect on screening procedure. In addition, the level of antagonism has been correlated with the observed inhibition of disease symptoms in wheat seedlings. The tested parameters strongly influenced the level of antagonism exhibited in dual culture. Interestingly, a wheat based medium could mimic the level of biocontrol exerted in planta against root rot. None of the in vitro assays could appropriately predict the activity of the streptomycetes against foot rot. The activity in planta cannot be effectively predicted by dual culture plate studies, therefore improved methods are needed to better mimic the activity of biocontrol strains in natural conditions. This work contributes to setting up laboratory standards for preliminary screening assays of Streptomyces BCAs against fungal pathogens.