EFFECTS OF SEED TREATMENT WITH SAN-789-F, A HOMOPROPARGYLAMINE FUNGICIDE, ON GERMINATION AND CONTENTS OF SQUALENE AND STEROLS OF WHEAT SEEDLINGS

Wheat seedlings (Triticum aestivum L. cv. Arina) contained mainly sito sterol and campesterol as the principal sterol compounds (71 and 21% o f the total amount of free sterols, respectively), whereas stigmastero l (3%) and other unidentified sterols (together 5%) were much less abu ndant. Squalene, an important intermediate of sterol biosynthesis, was only found in traces. Seed treatment with SAN 789 F thyl-3-hexynyl)-N -ethyl-1-naphthalenemethanamine), a homopropargylamine fungicide, indu ced two primary effects on sterol biosynthesis: First, squalene accumu lated temporarily in large amounts within 48 hr after treatment, indic ating an inhibition of squalene epoxidase; second, the content of free sterols slightly decreased within 14 days after treatment, probably a s a consequence of squalene epoxidase inhibition. An additional effect of the seed treatment was an inhibition of growth occurring immediate ly after germination, whereas later, seedlings started to regrow. In c ontrast to a seed treatment with a wettable powder formulation (10 WP) , seeds treated with an encapsulated ''slow-release'' formulation (CS 250) accumulated much less squalene. In addition, the growth of seedli ngs was only slightly inhibited by treatment with the CS 250 formulati on. A reduced growth inhibition was also achieved when seedlings were treated between 3 and 7 days after germination. These results suggest that accumulation of squalene rather than a deficiency of free sterols is responsible for the inhibition of germination induced by the treat ment with SAN 789 F. The inhibitory effects of the fungicide on growth and on squalene epoxidase were drastically reduced, when the homoprop argylamine delivery to the seed was delayed by either a late applicati on or the use of an encapsulated formulation. (C) 1995 Academic Press, Inc.