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 tissues of selected wild oat (Avena fatua L.) populations which were characterized to be either susceptible or resistant to the herbicide triallate. Gas chromatographic analysis of fatty acid methyl esters showed that these tissues contained fatty acids of chain length C14 to C24, but the major components were C18 (C18:2, C18:3 + C18:1) and C16 chain lengths. All the other fatty acid chains were present as very minor components. Application of triallate at a concentration equivalent to the recommended field rate in either a soil- or a filter paper-based system for seedling growth caused a significant (P 0.05) reduction in the level of all major fatty acids in the susceptible populations, but did not affect their levels in the resistant populations. In the susceptible populations, triallate also caused a significant increase in the level of C15 fatty acid. Application of difenzoquat (10 ppm), a herbicide to which triallate-resistant populations have shown cross-resistance, to young seedlings did not cause any significant change in the fatty acid composition of either susceptible or resistant populations. This would suggest that in these wild oat seedlings, fatty acid biosynthesis is not sensitive to difenzoquat; therefore, it may not be involved in cross-resistance to this herbicide