Archivio Journal of Plant Pathology

Abstract:

A foliar spray of a-aminoisobutyric acid (AIB) reduced the number, size and sporulation of powdery mildew colonies on wheat seedlings. Application of AIB one day before or after inoculation reduced severity of powdery mildew to a similar extent. Protection effectiveness depended on the concentration applied and time intervals between treatment and inoculation. Only concentrations higher than 50 mmol l-1 effectively protected seedlings. Microscopy investigations revealed no inhibition of conidial germination and penetration of the epidermal cells, but the development of haustoria was strongly affected. 14C-AIB was taken up rapidly by the primary leaf, translocated into the whole plant and accumulated in the newly developed shoot tissue. Quantitative data indicated that 39% of 14C-AIB applied remained on the surface of the treated primary leaf and 45% was retained by the plant tissue one day after treatment. The effectiveness of AIB in wheat against powdery mildew was associated with its concentration in the tissue. Thin layer chromatographic separation of the radioactive plant extracts revealed slow metabolism of AIB. A direct fungistatic effect on the fungus and alterations of plant metabolism caused by AIB are suggested as probable mechanisms of disease control.