A new race ofyellow rustthat infectsSolstice wheatis being investigated
byNIAB.
Samples taken during the
United Kingdom Cereal Pathogen Virulence Survey (UKCPVS) last
season from the variety have been confirmed as virulent also in
seedlings.
NIAB is now testing the isolates on adult plants in the field to
determine the level of susceptibility of Solstice and other
varieties to the race. Solstice was previously resistant to all
known yellow rust races.
Wheat growers also face a resurgence of older yellow rust races,
says NIAB, because of an increasing area of varieties with yellow
rust resistance gene Yr6.
"Despite predictions that yellow rust was unlikely to be a
problem because of the cold winter, outbreaks have been detected in
wheat crops particularly in the high risk areas of the East
Midlands and East Anglia," says NIAB's Rosemary Bayles. "Reports
suggest
Robigus and Oakley are particularly affected."
Robigus is extremely susceptible to a specific race that has
dominated the yellow rust population for several years. But Oakley
has remained largely free to date, so the appearance of the disease
may be more of a surprise to its growers.
But UKCPVS results suggest it is moderately susceptible to a
separate race of yellow rust, which although once quite common, has
become less frequent in recent years. Unlike the "Robigus race" the
types that infect Oakley carry virulence for the resistance gene
Yr6, says Dr Bayles.
"Our experience shows that as a variety becomes more widely
grown on farm, yellow rust races with corresponding virulence
rapidly become more common. We could, therefore, expect to see an
increase in Yr6-virulent races in response to increasing area of
Oakley, and this would account for the increased incidence of the
disease in this variety."
