Isolation and characterization of streptomycetes and pseudomonad strains with antagonistic activity against the plant parasitic nematode Pratylenchus penetrans and fungi associated with replant disease

Abstract Pratylenchus penetrans is one of the most important plant-parasitic nematodes causing losses in economically significant crops such as apple, cherry, corn, grapes, oat, onion, peach, potato, soybean, strawberry, and wheat. The objective of this study was to isolate and characterize plant growth promoting rhizobacterial (PGPR) strains from sweet cherry rhizospheres with biocontrol potential against P. penetrans, and to evaluate the antagonistic activity of the selected strains on a model plant (onion), in a growth chamber experiment. Five strains: three actinomycetes (Streptomyces fulvissimus A12, S. venezuelae A30, and S. annulatus A34) and two pseudomonads (Pseudomonas sp. P3 and P. donghuensis P17) with nematicidal activity were isolated. The selected PGPR strains decreased P. penetrans populations on onion roots and enhanced onion root length and dry weight. Among possible mechanisms of action, the strains displayed the capacity to produce nematicidal lytic enzymes such as chitinases and proteases, and form biofilms, which is an advantage in colonizing the plant rhizosphere. Some of them also showed antifungal activity against the phytopathogenic fungi Fusarium oxysporum C1-1, Ilyonectria macrodidyma C1-1, and Ilyonectria spp. C2-1 isolated from roots of cherry trees affected by replant disease . The multifunctionality of the strains, and the fact that they were isolated from the cherry rhizosphere, makes them good candidates to be used as biocontrol agents in sweet cherry orchards affected by P. penetrans.