Viruserkrankungen in Möhren - gegenwärtige Probleme und verfügbare Nachweismethoden

Summary

An apparently new virus disease of carrots (Daucus carota) has gained increasing importance in Germany. The complex of symptoms consisting of leaf reddening, plant stunting, hairy and rat tailed roots is thought to be caused by viral infections. Particularly the main carrot growing areas in Lower Saxony are adversely affected. In field surveys in 2003 about 30 % symptomatic plants were observed with average weight losses of about 30 %. In severe cases symptom-related yield reduction was estimated to be 17 % on-farm, which corresponded to a monetary loss of up to 600 €/ha. In 2004 up to 6 % of the plants displayed virus like symptoms. Varietal differences in susceptibility were observed. In general, late maturing varieties for processing showed more symptoms than early maturing fresh market varietes. However, this was not consistent in all cases.
At present eight different carrot viruses have been isolated and partially characterized. Antisera to Carrot yellow leaf virus (CYLV, Closterovirus), Carrot thin leaf virus (CTLV, Potyvirus), Carrot red leaf virus (CtRLV, Luteovirus), and the Anthriscus strain of Parsnip yellow fleck virus (PYFV, Sequivirus) are now commercially available for serological analysis of carrot samples. Our provisional experimental data indicate that CtRLV is highly variable and the causal agents typically associated with the carrot motley dwarf (CMD) disease complex may differ in Germany from those reported in the literature. Further analyses of single and multiple infections with their corresponding symptoms under controlled conditions will be necessary to identify the relevant environmental conditions leading to economic losses.