FATTY-ACID AND WAX BIOSYNTHESIS IN SUSCEPTIBLE AND TRIALLATE-RESISTANT AVENA-FATUA L

The recent characterization of triallate-resistant lines of wild oat ( Avena fatua L.) deficient in triallate sulfoxidation provides an exper imental system to investigate and differentiate the effects of trialla te and triallate sulfoxide on wax and lipid biosynthesis. Greenhouse a pplications of triallate dramatically reduced epicuticular wax deposit ion in susceptible (S) but not resistant (R) wild oats. Triallate trea tment had no effect on in-vivo concentrations of C-12 to C-26 fatty ac ids and fatty alcohols in R plants, while elongated fatty acid fractio ns (C > 18) were significantly reduced in S plants. In contrast, treat ment with triallate sulfoxide reduced in-vivo concentrations of elonga ted fatty acids equally in R and S, supporting the hypothesis that tri allate sulfoxide is more inhibitory than triallate towards fatty acid elongases. Although de-novo synthesis of short-chain fatty acids was n ot affected by triallate or triallate sulfoxide in R or S plants, synt hesis of elongated fatty acid fractions was dramatically reduced in S plants by triallate. Fatty acid biosynthesis in R and S plants was equ ally sensitive to triallate sulfoxide. The results support the idea th at in-vivo triallate sulfoxidation is necessary for herbicidal activit y, and confirm that reduced rates of triallate sulfoxidation confer re sistance in R wild oats.