The role of the preceding crop and weed control in the transmission of Rhizoctonia cerealis and R.solani to winter cereals

Winter cereals (wheat, triticale, rye, barley) grown in experimental fields were assessed for sharp eyespot. Preceding crops (spring cereals and fallow) and weed control (herbicides application, no control) were taken into account. The health status evaluation was carried out at the stem elongation phase and at the milk maturity stage. The macroscopic estimation was accompanied by the analysis of fungal species identified on stem bases and roots, which showed various disease symptoms. The analysis of fungal species from the genus Rhizoctonia were especially noted. Mycological analysis of roots was carried out at the seedling growth and stem elongation phase, and stem bases at the seedling growth and milk maturity stage. Infection caused by Rhizoctonia spp. was confirmed by polymeraze chain reaction (PCR) assay. The highest infection was noted on wheat followed by triticale, rye and barley. Occurrence of sharp eyespot depended more on weed control than on what the preceding crop had been. At the milk maturity stage, lower severity of sharp eyespot of triticale, rye and barley was noted on plots not treated with herbicides, and on wheat with herbicide application. The research showed a significant effect of the preceding crop only on the health status of wheat. At the milk maturity stage, the highest infection was noted after spring triticale and the lowest after oats. Stems of cereals with sharp eyespot symptoms and healthy stems were settled mainly by Rhizoctonia cerealis (wheat - 25.6%, triticale - 12.0%, rye - 22.2%, barley - 11.3%), rarely by R. solani (respectively 6.0, 4.0, 2.9 and 1.8%). Rhizoctonia solani was isolated more often from roots with true eyespot and Fusarium foot rot symptoms. It may suggest that R. cerealis was the main causal agent of sharp eyespot on all tested cereals. The preceding crop did not affect the composition of Rhizoctonia species