HCN-producing Pseudomonas protegens CHA0 affects intraradical viability of Rhizophagus irregularis in Sorghum vulgare roots.

Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria inhabit the plant rhizosphere. Both functional groups can influence plant community structures, and interactions between them can vary from being synergistic to antagonistic. HCN-producing Pseudomonas protegens CHA0 is a plant growth-promoting rhizobacterium. P. protegens CHA0 has been shown to weakly attach to AMF hyphae. Here, we analyze the effect of P. protegens CHA0 on the viability of intraradical AMF hyphae. Using pot experiments, we have grown mycorrhizal and nonmycorrhizal Sorghum vulgare var. M35 with P. protegens CHA0 or HCN mutant P. protegens CHA77, which did not produce HCN. Mycorrhizal and nonmycorrhizal Sorghum grown without CHA0 or CHA77 served as the control. While metabolically active AMF was not detected in mycorrhizal plants grown with HCN CHA0, the percentage of root colonization of metabolically active AMF in plants grown with HCN CHA77 was lower than in the control. Root phosphorus was highest in mycorrhizal plants grown with HCN CHA0, but root Fe was higher in plants grown with the bacterial strains. Our results indicate that HCN-producing P. protegens can affect the viability of intraradical AMF.