VIRAL DISEASES ON CEREALS IN CENTRAL HUNGARY

Abstract

In recent years viral diseases have become more frequent on cereals in Hungary. In the breeding nursery of the Martonvásár Institute, which contains stocks with very diverse genetic backgrounds, wheat suffered major attacks by viruses in 1972, 1976, 1980, 1981, 1982, 1986, 1990, 1996 and 1998. The winter barley plots incurred great damage in 1989 and 1990, while a large proportion of the durum wheat was destroyed in 1996. In 1982 barley yellow dwarf virus caused an epidemic in Fejér County and on many farms the damage was so great that the fields had to be ploughed up. The following nine viruses, which impose a threat to cereals, have been identified in Hungary to date: 1966: barley yellow dwarf luteovirus (BYDV), 1984: barley stripe mosaic hordeivirus (BSMV), 1985: wheat streak mosaic tritimovirus (WSMV), 1986: brome mosaic bromovirus (BMV), cocksfoot mottle sobemovirus (CfMV), 1988: wheat dwarf mastrevirus (WDV), 1989: barley yellow mosaic bymovirus (BYMV), 1990: agropyron mosaic rymovirus (AgMV) and ryegrass mosaic rymovirus (RyMV). The most frequent and widespread of these are BYDV and WDV, which are thus able to cause the greatest quantitative and qualitative damage. On the basis of six years’ data (1994–2000), neither BYDV nor WDV could be isolated from 35.7% of 1163 samples exhibiting leaf yellowing and dwarfness. This indicates that other viruses pathogenic to cereals can induce similar symptoms. Among the plants showing symptoms of virus infection, 47.3% were attacked by WDV alone, in proportions ranging from 28.8% in barley to 69.7% in triticale. The degree of infection changed from year to year: WDV was isolated from 0.0% of symptom-exhibiting plants in 1999, from 48.5% in 1997 and from 94.0% in 2000. Barley yellow dwarf virus was only isolated alone from 9.5% of the samples, while it was isolated together with wheat dwarf virus from 7.5% of the samples. Considerable differences were observed between the cereal species: only 5.6% of the durum wheat samples were infected with BYDV, while this figure was 28.1% for oats. There was also a significant year effect. In 1996 triticale was not infected, while in 2000 5.0% of the plants exhibited symptoms and in 1994 45.5% of the plants were hosts to the BYD virus. Under Hungarian conditions all five known serotypes can be found, though in different proportions depending on the cereal species and the year. The most frequent is RPV (27.4%), followed by PAV (26.9%), SGV (15.6%), MAV (15.3%) and RMV (14.8%). In samples collected from oats only the PAV serotype was found. The MAV serotype has never been isolated from triticale. The dominant serotype was RPV (60.7%) in wheat samples, SGV (36.0%) in durum wheat and RMV (29.1%) in barley.