Fungal communities associated with field grown oilseed rape (Brassica napusL.) – their possible role in early crop establishment

Problems with patchiness due to delay in emergence or poor crop establishment are not uncommon in oilseed rape cultivation. Our aim was to study the fungal communities associated with field grown oilseed rape and to explore their role in emergence and early crop establishment. This study was carried out by characterising the fungal communities in roots and rhizosphere soils of both spring and winter oilseed rape. The fungal communities were analysed using both culture-dependent and culture-independent approaches. Sampling was carried out in field plots with clear differences in crop establishment. Phylogenetic comparison of the fungal communities in different environments revealed significant differences between roots and rhizosphere soils. In winter rape, the fungal communities in the poor-emergence plots differed significantly from that found in normal-emergence plots, while in spring rape this difference was less prominent. However, in a combined statistical analysis of data from both winter and spring rape, the fungal communities in poor- and normal-emergence plots differed significantly. In follow-up studies, putatively pathogenic fungi were isolated from poor-emergence plots. Their effects on emergence and seedling growth were evaluated in the two crop types in greenhouse experiments. Rhizoctonia solani was found only in roots from poor-emergence plots, and was also demonstrated to be highly pathogenic on oilseed rape independent of cultivars when tested in greenhouse trials. The results from the fungal community analysis and from the greenhouse experiments are discussed in relation to their role in crop establishment related problems in oilseed rape.