EFFECTS OF TRIALLATE AND DIFENZOQUAT ON FATTY-ACID COMPOSITION IN YOUNG SHOOTS OF SUSCEPTIBLE AND RESISTANT AVENA-FATUA POPULATIONS

The composition of fatty acid moieties was similar in young shoot tiss ues of selected wild oat (Avena fatua L.) populations which were chara cterized to be either susceptible or resistant to the herbicide triall ate. Gas chromatographic analysis of fatty acid methyl eaters showed t hat these tissues contained fatty acids of chain length C14 to C24, bu t the major components were C18 (C18:2, C18:3 +C18:1) and C16 chain le ngths. All the other fatty acid chains were present as very minor comp onents. Application of triallate at a concentration equivalent to the recommended field rate in either a soil- or it filter paper-based syst em for seedling growth caused a significant (P < 0.05) reduction in th e level of all major fatty acids in the susceptible populations, but d id not affect their levels in the resistant populations. In the suscep tible populations, triallate also caused a significant increase in the level of C15 fatty acid. Application of difenzoquat (10 ppm), a herbi cide to which triallate-resistant populations have shown cross-resista nce, to young seedlings did not cause any significant change in the fa tty acid composition of either susceptible or resistant populations. T his would suggest that in these wild oat seedlings, fatty acid biosynt hesis is not sensitive to difenzoquat; therefore, it may not be involv ed in cross-resistance to this herbicide. (C) 1997 Academic Press.