During June and July of 2004, several diseased plants in winter wheat (Triticum aestivum L.) were reported by agricultural advisers in the southern and southwestern coastal area of Finland. The plants showed extreme dwarfing, various yellowing symptoms, and reduced or no heading. The damage varied considerably. Yield loss estimates in direct-drilled winter wheat fields were approximately 20 to 40% and in worst cases as much as 100%. A few leafhoppers (Psammotettix alienus Dahlb.) were collected from the field with sweep nets and yellow traps. Roots and symptomatic leaves of winter wheat and the leafhoppers were first tested using a commercial polyclonal antibody (DSMZ, Braunschweig, Germany) specific for Wheat dwarf virus (WDV). For the leaf and root samples, routine double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) procedures were used. Five leafhoppers per sample were homogenized with the extraction buffer provided. The homogenate was centrifuged and the extract was evaluated using DAS-ELISA (2). The highest absorbance values were obtained from leafhoppers suspected to be viruliferous. The mean values varied from 1.002 to 1.990 after incubation in the substrate for 2 h. The absorbance values of several leaf samples exceeded the virus-positive threshold but were lower than those of the viruliferous leafhoppers. The virus was not detected in roots. Low absorbance values of virus-positive plants were confirmed using polymerase chain reaction (PCR) with primers specific for WDV (1). Total DNA extracts (DNeasy Plant Mini Kit; Qiagen, Hilden, Germany) from symptomatic leaves were tested using puRe Taq Ready-To-Go PCR beads (Amersham Biosciences, Buckinghamshire, UK). The PCR amplicon was the expected size (1,201 bp). The high absorbance value of the leafhoppers showed that the leafhoppers were carriers of the virus. These results confirmed that the causal agent of dwarfing and yellowing symptoms in winter wheat was WDV (genus Mastrevirus, family Geminiviridae).
References: (1) A. Kvarnheden et al. Arch Virol 147:205, 2002. (2) J. Vacke and R. Cibulka. Plant Prot. Sci. 35:41, 2000.
