Wheat crops face threat of new yellow rust race

1 May 2009

The National Institute of Agricultural Botany is investigating a potential new race of yellow rust on winter wheat. 

In 2008 the United Kingdom Cereal Pathogen Virulence Survey (UKCPVS) collected two isolates of yellow rust from Group 1 wheat Solstice and confirmed that they were virulent on seedlings of the variety.  Solstice currently has a resistance rating of 9 and, until last season, was resistant to all known races of yellow rust. 

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 yellow rust race.

Wheat growers also face a resurgence of older races of yellow rust.  NIAB’s Dr Rosemary Bayles attributes this to an increasing area of varieties with the yellow rust resistance gene Yr6.

“Despite predictions that yellow rust was unlikely to be a problem because of the cold winter, outbreaks of the disease have already been detected in wheat crops particularly in the high risk areas of the East Midlands and East Anglia.  Reports suggest that Robigus and Oakley are particularly affected at present,” says Dr Bayles.

Robigus, with a rating of 2, is extremely susceptible to a specific race that has dominated the yellow rust population for several years now.  However, Oakley has remained largely free to date, so the more widespread appearance of the disease in crops has perhaps come as more of a surprise to growers.

UKCPVS results show that Oakley, with a rating of 6, is moderately susceptible to a separate race of yellow rust, which, although once quite common, has become less frequent in recent years.  Unlike the common ‘Robigus race’ the types that infect Oakley carry virulence for the resistance gene Yr6.  These are the races that infected older varieties including Madrigal, Access and Napier as well as more recent ones such as Mascot and Einstein.

“Our experience shows that as a variety becomes more widely grown on farms, yellow rust races with corresponding virulence, capable of infecting the particular variety, rapidly become more common.  We would therefore expect to see an increase in Yr6-virulent races of yellow rust in response to the increasing acreage of Oakley – and this would account for the increased incidence of the disease in this variety,” says Dr Bayles.

For further information contact:
Dr Rosemary Bayles, NIAB
T: 01223 342211
E: rosemary.bayles [at] niab.com ()

Issued by:
Ros Lloyd, Front Foot Communications            
T: 01487 831425     
E: ros.lloyd [at] frontfoot.uk.com ()