Impact of late season heat stress on the phenology and reproductive biology of Avena sterilis ssp. ludoviciana

Abstract

Avena sterilis ssp. ludoviciana (wild oat) is considered to be the most difficult-to-control winter weed in the no-tillage-based conservation cropping systems of Australia's northern grains region (NGR). The increasing frequency of hot periods during the late winter/early spring season might be responsible for early shedding and less dormant seeds. This greater rain of less dormant seed may be better suited to the non-burial conditions of no-tillage and will be ready to reinfest during a subsequent autumn-sown crop. To examine this possible mechanism of persistence, an experiment was conducted using wild oat biotypes collected from northern and southern areas of the NGR. At the time of wild oat panicle initiation a portion of the plants were transferred from an ambient temperature greenhouse (23/14°C day/night) to a high temperature glasshouse (29/23°C). The process of moving plants was repeated on three further occasions, each ten days apart. Plants exposed early to heat stress matured 17 days earlier and produced less filled (28% less), smaller (34% smaller) spikelets with less dormant seeds (34% less) compared with control plants. The biotypes coming from the northern NGR maturated five to eight days earlier than the biotypes from the southern NGR. It is hypothesised that the increasing frequency of late season hot periods, coupled with no-tillage-based conservation cropping systems that do not bury seeds deep in the soil profile, is facilitating the persistence of species like A. sterilis ssp. ludoviciana in the NGR.