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Regional distribution of soilborne diseases in cereal crops in Australia

Gupta Vadakattu: CSIRO

<div>Soilborne root diseases are major constraints for Australian cereal production, with >$400 million annual costs. Cereals cropped continuously are at high risk from soilborne diseases. A multi-disciplinary national project was initiated in 2014 to understand the extent of yield gap in rainfed cereal crops, and identify factors driving yield limitations across Eastern, Southern and Western grain production regions. During 2015 to 2017 crop seasons, wheat and barley root samples were collected at GS31 stage from paired fields (50 plants from five GPS locations on a 100M transect from up to 120 farms p.a.). Roots were scored for the presence and severity of diseases and overall seminal and crown root health (0-5 scale). Eight soilborne root diseases were recorded, and only a few fields (<20%) had plants without disease symptoms. Multiple diseases in a single field and agro-ecological region based distribution of specific diseases were commonly observed. Significant levels of soilborne pathogens (PredictaB<sup>®</sup> DNA test) were found in the pre-crop soil samples. Root rot diseases caused by <em>Rhizoctonia solani</em> AG8, <em>Fusarium</em> <em>pseudograminearum</em>, <em>Pythium</em> spp. and root lesion nematode were the most common. Take-all and <em>Bipolaris</em> root rot were also observed in multiple regions. Brown root rot (<em>Phoma scleroitedes</em>) less commonly recorded. These observations coupled with water-limited yield estimations indicate that root diseases may cause significant portions of the yield gaps in wheat and barley crops. In-crop root assessments are compared with pre-crop pathogen DNA inoculum data to identify links with soil and environmental factors affecting disease impacts.</div>