Knowing what blight strain is present in a potato crop mid-season and its sensitivity to fungicides,
could help growers take more prompt action to combat the disease.
AHDB’s Fight Against Blight service is offering in-season genotyping for the first time this year, following a three-year agreement with the James Hutton Institute to carry out the work.
Growers and agronomists will be able to continue submitting blight samples for analysis as well as fungicide testing. Until now, they have had to wait until the end of the season, after implementing a blight spray programme, to receive results from samples submitted. However, the aim of the new service is to report back earlier, enabling growers to use the genotyping data to inform their blight management decisions during the current season, says AHDB.
Samples will also be studied to identify changes in fungicide sensitivity or new virulence that overcomes key sources of late blight resistance in potato cultivars and report them to key stakeholders to underpin successful Integrated Pest Management (IPM) practices in the potato industry, it adds.
Data from AHDB’s Fight Against Blight service shows an increase in a new blight genotype found in outbreaks from last year, despite the hot and dry conditions experienced.
The warmer weather saw fewer samples submitted to Fight Against Blight compared with the 2017 growing season. However, isolates of the 36_A2 genotype found in the samples increased by 15 percentage points compared with the two per cent found in 2017.
While researchers are still trying to build up a full picture of this genotype, the increase in frequency of 36_A2 in an overall low blight pressure year and its spread in continental Europe suggest it is causing an aggressive form of blight, according to AHDB.
Results from INRA, (French National Institute for Agricultural Research) which has tested blight isolates for aggressiveness, found that 36_A2 produced the largest lesions, as well as the most spores per lesion of the samples tested.
Research at the James Hutton Institute showed that the genotype was more difficult to inhibit than other lineages, producing the largest lesion sizes under the lowest doses with the four key fungicide active ingredients used to combat blight. As the doses applied were well below the rates applied in the field, the data do not give evidence of 36_A2’s resistance to the fungicides used, says AHDB.
So far 36_A2 has established itself in the East of the UK but has not yet been found further north than Lincolnshire or in the North or West, it adds.