It's a mystery: Why is there disease present in cereal roots in the absence of pathogen DNA in the soil?
Hüberli, D., Collins, S., Connor, M., MacLeod, W., Correll, R. and McKay, A. (2014) It's a mystery: Why is there disease present in cereal roots in the absence of pathogen DNA in the soil? In: 8th Australasian Soilbourne Diseases Symposium, 10 - 13 November, Hobart, Tasmania.
Cereal paddocks with high incidence of symptoms typical of Rhizoctonia solani infection, but from whose soil no Rhizoctonia solani DNA was detected in three years, were identified in W A. An intensive soil and plant survey was conducted at two such sites (problem paddocks), and one site with high levels of Rhizoctonia root symptoms and high soil DNA. During the 2014 growing season, each of the three paddocks were assessed at monthly intervals to identify changes in pest and disease incidence and severity, for both Rhizoctonia and root lesion nematode (RLN, Pratylenchus neglectus). Between June and October, a series of transect assessments was conducted for soil and plants on and off the cropping row. A 25 cm core was also taken at each transect and the sample divided into five 5 cm sections to determine if the presence of Rhizoctonia and RLN changed with soil depth. Stubble, where present, was also collected. In June, Rhizoctonia DNA was detected at very low levels in only 1 out of 20 transects in the two problem paddocks, while the confirmed paddock had DNA detections in 18 out of 20 transects. Nematodes were detected in low levels at 4 out of 20 transects at one problem paddock, and 19 out of 20 in the other. The confirmed paddock had mostly high levels of nematodes at all 20 locations. On and off row sampling was not significantly different for Rhizoctonia, but was for nematodes. Stubble addition did not change the detection of either Rhizoctonia or nematodes.
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