Agave palmeri is a large succulent native to the Sonoran and Chihuahuan Deserts of North America. Some of the bacterial endophytes present in Agave palmeri seeds have been identified as fluorescent Pseudomonas spp. While there is already great interest in using Pseudomonas as biocontrol agents and biofertilizers to replace traditional pesticides and fertilizers, Pseudomonas endophytes from desert plants have not yet been investigated for their biocontrol and biofertilization capabilities. The objective of this study is to assess the root growth promotion and biocontrol capabilities of agave endophytic Pseudomonas spp. when inoculated into crop plants such as carrot, coriander, and rice.
Results/Conclusions
Every isolated strain of Pseudomonas spp. inhibited the hyphal growth of Fusarium oxysporum and Cercospora spp. on agar, though the extent of inhibition varied depending on the strain. Several strains colonized fungal mycelia and the strains with the highest antifungal capabilities caused hyphal degradation in a manner reminiscent of cell lysis. Surface-sterilized crop seedlings inoculated with Pseudomonas spp. show faster growth, enhanced root growth, greater root branching, increased root exudate production, and increased soil aggregate formation around the root compared to non-inoculated controls. When grown in soil inoculated with F. oxysporum, Pseudomonas-inoculated seedlings showed less signs of disease in addition to enhanced root growth and root exudate production. This effect also occurs in seeds inoculated with a simulated Pseudomonas microbiome composed of four different strains.
These preliminary results indicate that endophytic fluorescent Pseudomonas from Agave palmeri have the potential to be used as both a biostimulant and a bioprotectant in a non-host-specific manner in crop plants.