Effects of elevated temperature and α-aminooxyacetate on the accumulation of avenalumins in oat leaves infected with Puccinia coronata f. sp. avenae

Abstract

The rapid accumulation of avenalumins in incompatible crown rust-infected Shokan 1 oat leaves which occurred at 20 °C was greatly inhibited when infected plants were grown at 25 to 35 °C. At 30 °C, avenalumin accumulation was almost totally inhibited and much greater hyphal growth occurred than at 20 °C. When infected plants were grown at 20 °C for 36 h and then transferred to 30 °C, most of the previously-accumulated avenalumins disappeared rapidly within 48 h and hyphal growth continued. However, no subsequent hyphal growth resulted when the plants were transferred to 30 °C at 72 h after inoculation. Treatment of plants with α-aminooxyacetate, a potent competitive inhibitor of phenylalanine ammonia-lyase, greatly inhibited the rapid accumulation of avenalumins in normally incompatible interactions. This was correlated with an increase in susceptibility of the host plants. Significant inhibition of avenalumin accumulation was observed 48 h after inoculation when inoculation was followed by application of the inhibitor at 10 μ m, but much less inhibition of hypersensitive host cell collapse occurred in the treated leaves. These facts suggest that rapid and large accumulation of the avenalumins is crucial for resistance expression in oat leaves against an incompatible crown rust race.