Myxobacteria as a potential biocontrol agent effective against pathogenic fungi of economically important forest trees

The broad biocontrol properties of myxobacteria (mainly members of the genera Corallococcus and Myxococcus) isolated from forest soils against main fungal pathogens of pine seedlings were estimated. Among the myxobacterial strains studied (in vivo tests), the strongest antagonism towards fungi was noticed for the strains of the species Myxococcus virescens Thaxter and Corallococcus exiguus Reichenbach. They inhibited the fungal growth within the range 38–63%. The strongest inhibitory reaction towards Cylindrocarpon destructans (Zinssm.) Scholten was observed. A predominating part of myxobacteria (22 from among 30) inhibited the growth of Rhizoctonia solani Kühn. Myxobacteria suppressed any pathogenic action of Rhizoctonia solani (strain 411) towards Scots pine seedlings (in vitro tests). They produced extracellular (but not intracellular) acidic and neutral proteinases. None of the myxobacterial strain under examination produced chitinases. The 57% of the myxobacterial strains studied produced siderophores. The numbers of myxobacterial strains, obtained from under forest trees were in the following order: Betula pendula Roth. > Pinus sylvestris L. > Alnus glutinosa Gaertn. = Quercus robur L. The results gained in present work have proved potential use of myxobacteria as biocontrol agents against Rhizoctonia solani, common fungal pathogen of pine seedlings.