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Doctoral thesis, 2022

Epidemiology of wheat dwarf virus

Yazdkhasti, Elham


In Sweden and many other parts of Europe, wheat dwarf is one of the most important diseases induced by a plant-infecting virus. Wheat dwarf disease is caused by wheat dwarf virus (WDV), transmitted by the leafhopper Psammotettix alienus.  Our study provides the evidence that WDV, barley yellow dwarf viruses (BYDVs) and cereal yellow dwarf virus (CYDV) infect ryegrass growing in or around winter wheat fields. Phylogenetic analysis showed that a ryegrass isolate of WDV was a typical WDV-E isolate closely related to isolates infecting wheat and the isolate of BYDV-PAV grouped in a clade together with other BYDV-PAV isolates, suggesting that the same virus genotypes infecting the ryegrass can be found in wheat as well as in other host plants and the insect vector. Inoculation experiments confirmed that various genotypes of annual ryegrass can be infected with WDV to a very low titre. The results showed that leafhoppers also can acquire a low titre of WDV from infected ryegrass plants, and efficiently transmit it to wheat. Moreover, domesticated bread wheat (Triticum aestivum) and its wild relatives responded differently to WDV infection. Aegilops tauschii, Triticum urartu and the bread wheat cultivar Tarso exposed to the viruliferous leafhoppers had different virus content in roots and in each leaf at different time points. Between the accessions, Ae. tauschii stood out as the WDV accumulation and symptom development started later compared to T. urartu and bread wheat. As a result, Ae. tauschii followed a normal growth pattern and developed milder symptoms. Infected plants of T. urartu and wheat could not develop normally as compared to non-infected plants. In addition, infected plants of Ae. tauschii showed less reduction in leaf fresh weight over time compared to the other accessions. This finding introduces Ae. tauschii as a candidate for further studies on WDV-resistance. PCR test results for presence of WDV in leafhoppers collected from different counties in Sweden, together with known disease incidence and records of weather conditions, showed that disease occurrence and severity in winter wheat fields varied considerably between years, regions, and locations. The results suggest a strong correlation between the number of P. alienus leafhoppers and disease incidence in Uppsala, Stockholm and Västmanland. For the autumn, the number of leafhoppers per field was found to be positively linked to weekly average temperature as well as average weekly maximum and minimum temperature. In conclusion, the results of this thesis has uncovered the elements influencing the epidemiology of WDV which is important for control of the disease.


Epidemiology; Geminivirus; Mastrevirus; Psammottetix alienus; ryegrass; wheat; Wheat dwarf virus

Published in

Acta Universitatis Agriculturae Sueciae
2022, number: 2022:55
ISBN: 978-91-7760-985-8, eISBN: 978-91-7760-986-5
Publisher: Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Agricultural Science

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