In cereals, soil‐borne viruses transmitted by the plasmodiophorid Polymyxa graminis (e.g., Barley mild mosaic virus, Barley yellow mosaic virus or Soil‐borne cereal mosaic virus), have increased in importance due to the increase of the acreage infested and because yield losses cannot be prevented by chemical measures. Due to global warming, it is also expected that insect transmitted viruses vectored by aphids (e.g., Barley yellow dwarf virus, Cereal yellow dwarf virus), leafhoppers (Wheat dwarf virus) or mites (e.g., Wheat streak mosaic virus), will become much more important even in cooler regions. The environmentally most sound and also most cost effective approach to prevent high yield losses caused by these viruses is breeding for resistance. Therefore, in contrast to other reviews on cereal viruses, this study briefly reviews present knowledge on cereal‐infecting viruses and emphasizes especially the sources of resistance or tolerance to these viruses and their use in molecular breeding schemes.

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The distribution of various Beet necrotic yellow vein virus (BNYVV) genotypes was studied using beet samples received from Germany and neighbouring countries. Almost exclusively B type BNYVV was detected in Germany, whereas in neighbouring countries BNYVV A types with different compositions of the amino acid tetrad in positions 67-70 of the RNA-3-encoded P25 are widely distributed. Neither A types nor the P type have been able to become established in Germany in the past decades, although there must have been many opportunities for their introduction from neighbouring countries. In one field, however, an RNA-5-containing BNYVV genotype closely resembling the Chinese isolate Har4 was found.

Selection of main cool‐season turfgrasses (perennial ryegrass and red fescue) for resistance to red thread disease caused by Laetisaria fuciformis has not progressed during the last 30 years because of low reproducibility of experiments carried out under natural infection. In this study, evaluation of a set of the turfgrass cultivars, including non‐host fodder grasses as control, was performed in a climatic chamber, a cold house and in the field using three types of artificial inoculum, and correlations between trials were analysed. In general, cultivars of Festuca rubra were more susceptible to the disease but differentiated better than cultivars of Lolium perenne. Significant interactions between cultivars of L. perenne and F. rubra and isolates of L. fuciformis were found. The fungus was also able to colonize leaves of sow thistle and wheat seedlings. In field conditions and in the glass cold‐house Dactylis glomerata was found to be relatively resistant to red thread disease. A possible selection programme is proposed.

The plasmodiophorid Polymyxa graminis transmits plant viruses to cereal crops such as wheat, rye, barley and triticale. Soil samples from different locations and cereal host plants were analyzed for the presence of P. graminis ribotypes I and II, and tested for the occurrence of soil-borne viruses. P. graminis sequences mainly from fields in Germany used for virus resistance trials, but also from a site each in Poland and Denmark were obtained and deposited in the European Nucleotide Archive. The interactions between the components of the pathogen complex -vector ribotype and virus -and the host are discussed.