[Effect of phosphate on the biosynthesis of tentoxin by Alternaria alternata (Fr.) Keissler]

Alternaria alternata (Fr.) Keissler produces a phytotoxic substance tentoxin. The influence of inorganic phosphate on the formation of this secondary metabolite was analyzed. Distinct phases of growth and metabolite formation can be defined. The first phase shows exponential growth, high QO2, protein and nucleic acid values and a rapid uptake of inorganic phosphate from the medium. The second phase shows linear growth and active tentoxin formation takes place. The highest yields of tentoxin are obtained, when inorganic phosphate in the medium was limited. The phosphate level also influences the ATP-pool of the mycelium. The role of ATP as an effector in phosphate mediated control of tentoxin synthesis was discussed.