Enhanced maize productivity by inoculation with diazotrophic bacteria

The objective of this work over the last 3 years was to identify maize-endo phyte associations with increased plant productivity compared with uninocul ated controls. We have used a collection of endophytes isolated by several groups. The experiments were done under field and greenhouse conditions in the presence or absence of added fixed nitrogen (N). Significant yield enha ncements of N-fertilized maize were obtained with bacterial endophytes that we have isolated from N-efficient lines of maize (such as Klebsiella pneum oniae 342) or switchgrass (Pantoea agglomerans P101 and P102). Several othe r strains from other groups were also tested with our best yield enhancemen ts from two Brazilian strains, Gluconacetobacter diazotrophicus PA15 and He rbaspirillum seropedicae Z152. Field experiments in Wisconsin were conducte d in 1998, 1999 and 2000 and in an additional four states (Illinois, Iowa, Indiana and Nebraska) in 2000, with a minimum of two elite lines of maize a t each site, each year. No strains were capable of relieving the N-deficien cy symptoms of unfertilized maize in either the field or the greenhouse.