Acetylene reduction by bacteria isolated from the rhizosphere of wheat

An asymbiotic bacillus possessing N₂-ase activity and capable of growth on low-N media was consistently isolated from the rhizosphere of a chromosome substitution line of spring wheat in which a pair of chromosomes 5D from the cultivar Rescue had been substituted for those of ‘Cadet’. None of the bacilli were isolated from either of the two parent cultivars, Rescue and Cadet, or from the corresponding substitution line involving a homoeologous chromosome 5B. Maximum C₂H₂ reduction to C₂H₄ by pure culture isolates was found to occur at a partial pressure of 0.2 atm C₂H₂. C₂H₂ reduction was diminished in the presence of O₂ and nearly ceased at a partial pressure of 0.08 atm O₂.The data presented suggest that altering the genetics of the wheat plant can change the root environment to favor the establishment of bacilli that exhibit N₂-ase activity in pure culture.