Followingthe mild, wet winter, significant disease pressure is forecast this spring.Varietal resistance is a key part of disease control so HGCA has today issuedan article, Understanding RLdisease ratings,which explains how the ratings are worked out.
Onthe Recommended Lists disease ratings are on a scale from 1 (high disease) to 9(low disease). The system is easy to use when choosing and managing crops butbehind the numbers there is a great deal of research to make sure the ratingsare right.
Whenmaking the disease ratings its really important to bring out the differencesbetween varieties so that growers have as much information as possible, forthis a large dataset is essential, explains Dr Jenna Watts of HGCA.
Fordiseases where we have a very large data set like Septoria tritici, orwhere there is the potential for changes in pathogen races such as rusts we usedata from three seasons. For other diseases we look at the last five seasons.
Inthe Recommended List there are, in fact, three different types of trial thatgive disease data.
Untreated replicated untreated trials
Diseaseobservation plots single replicate untreated trials
HGCAplaces great value in the results from inoculated trials as there is highdisease pressure which pulls out differences between varieties, says Dr Watts.For rust inoculated trials, the UKCPVS provides isolateswhich are characterised and are representative of current UK populations.
In July, HGCA will start to analyse datafrom the Recommended List trials to produce disease ratings for the nextRecommended Lists. In the meantime, ratings form the current 2014/15 RecommendedListscan help guide varietal choice and management in the coming season.
However, it is important to note that theseratings are calculated from 2009-2013 trial data and not the current season.Therefore, it is necessary to monitor all crops, even those with a high diseaserating, for diseases such as the rusts, where new races can rapidly eroderesistance, concludes Dr Watts.