Partial resistance to Wheat dwarf virus in winter wheat cultivars

Four Hungarian winter wheat cultivars were investigated for their susceptibility to the geminivirus Wheat dwarf virus (WDV). Previously, two cultivars (Mv Regiment and Mv Emese) were assessed by breeders to exhibit virus symptoms in the field, whereas Mv Dalma and Mv Vekni showed few symptoms. Two inoculation techniques for WDV, vector transmission with the leafhopper Psammotettix alienus and agroinoculation, were used. Leafhopper transmission was more efficient than agroinoculation. However, irrespective of the technique used, no Mv Dalma or Mv Vekni plants showed clear WDV symptoms. In contrast, 3/30 Mv Emese and 4/36 Mv Regiment plants showed dwarfing and chlorosis after agroinoculation and 13/17 and 14/15 plants, respectively, had clear WDV symptoms after vector transmission. WDV-specific PCR showed that Mv Vekni and Mv Dalma plants could be infected, especially following vector transmission (approximately 50% infection), but at significantly lower frequency than Mv Emese or Mv Regiment plants (100% infection). Furthermore, real-time PCR showed that WDV DNA accumulated to much lower levels in infected Mv Vekni and Mv Dalma plants than in infected Mv Regiment and Mv Emese plants. The data strongly suggest that Mv Vekni and Mv Dalma are partially resistant to WDV infection. As WDV resistance has not previously been identified in wheat, and because WDV can cause significant yield losses, the resistance of Mv Vekni or Mv Dalma will provide a valuable breeding resource.