Stem health label helps identify best disease-resistant osr varieties - farmers weekly

© A new Stem Health score is set to help growers identify the best oilseed rape varieties to grow with good resistance against three key yield-sapping stem diseases. Limagrain arable

technical specialist Liam Wilkinson says that keeping stems as green as possible enables crops to reach their yield potential, “so any nitrogen in the crop goes up into seed, maximising

yield and oil content”. See also: Tips on getting the most from clubroot-resistant OSR varieties There are four key stem diseases in oilseed rape: phoma/stem canker, cylindrosporium (light

leaf spot), verticillium wilt and sclerotinia. However, sclerotinia can be easily managed with fungicides, so the focus is on the other three diseases (see table), which can lead to yield

losses of 25%-50% in heavy cases. Mr Wilkinson says enhanced genetics is the most effective solution. THREE KEY STEM DISEASES OF OILSEED RAPE DISEASE PHOMA/STEM CANKER (PHOMA LINGAM)

CYLINDROSPORIUM (CYLINDROSPORIUM CONCENTRICUM) VERTICILLIUM WILT (VERTICILLIUM LONGISPORUM) FAVOURABLE CONDITIONS Warm and wet conditions in autumn and spring Windy and rainy conditions

during autumn and spring (5-15C) Light soils, medium soil moisture, warm temperature (>20C) IMPACT ON YIELD Up to 50% yield loss in heavy cases Up to 25% yield loss in heavy cases Up to

30% yield loss in heavy cases CHEMICAL SOLUTIONS Fungicide available, medium efficiency Fungicide available, low efficiency No chemical solution GENETIC SOLUTIONS Good level of resistance

available The breeder has developed a robust classification and assessment of varieties and only the top ones will be labelled with the Stem Health label. High resistance to all three

diseases is mandatory to get the Stem Health label, therefore, only one single weakness leads to exclusion from the Stem Health list. For example, Limagrain marketing manager Will Charlton

points to Wagner, which has good phoma (6) and excellent light leaf spot (7) scores, but its verticillium wilt resistance does not meet the threshold. “It’s not a bad variety, but growers

should avoid growing it on land where verticillium wilt is known to be a problem. That’s why its suited for growing in the north.” Attica, which is Limagrain’s highest yielding variety on

the current Recommended List, does meet the threshold for all three, so can be grown across the UK. Recommended List variety Auckland also carries the label. Seed is available for drilling

this summer and Mr Charlton believes Attica could take up to 10% of the certified seed market share. Four candidate varieties have also got the Stem Health labels. AHDB TOP-YIELDING VARIETY

ON  AHDB RECOMMENDED LIST FOR THE UK VERSUS STEM HEALTH VARIETIES Trait Turing Attica (Stem Health) Auckland (Stem Health) Gross output UK (%) 107 107 106 Stem stiffness 8 8 7 Light leaf

spot 7 7 7 Phoma 5 7 7 _On a scale of 1-9, where 9 expresses the characteristic the strongest_