Morphological and molecular characterisation of 'Echinochloa' species in the northern grain region of Australia and implications for weed management

Barnyard grasses ('Echinochloa' species) occur as major summer weeds in farming systems of the northern grain region (NGR) of Australia. Farmers report difficulty in achieving effective control of 'Echinochloa' using current management practices, with varied levels of success being reported. This study was undertaken to identify what species were present in the farming systems of the NGR, and to investigate if the varied levels of control could be attributed to morphological variations and/or the genetic diversity present within populations. It is important to identify correctly the 'Echinochloa' species present in order to achieve better control and reduce the current threat of glyphosate resistance evolution in these weeds in the NGR. This study commenced at the end of 2004 with field surveys being undertaken at three major cropping centres of the NGR; Wowan (central Queensland), Dalby (southern Queensland) and Narrabri (northern New South Wales). Two species were identified as occurring in the NGR, 'Echinochloa colona' (L.) Link and 'Echinochloa crus-galli' (L.) Beauv.. 'Echinochloa colona' was the most widespread species accounting for 93 percent of the plants sampled. Both species were morphologically diverse across the region with 'E. colona' categorised into 20 growth categories and 'E. crus-galli' into six categories. The most common growth form in 'E. colona' was semi-erect to prostrate (50%) while the majority of 'E. crus-galli' plants were erect (84%)