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15 Jun 2022

Honing in on stem health

As featured in Arable Farming Magazine

Honing in on stem health

by Arable Farming Magazine OSR May 2021 issue

With 20-plus varieties of OSR in its portfolio and 10 of the 14 varieties on the AHDB RL, Limagrains breeding programme is well refined.

With a focus throughout its portfolio on security, with all-round disease resistance and stacked traits, Limagrain is now setting its sights on breeding to further improve the overall health of the crop.

Stem health is an holistic term, not seen or measured on the Recommended List (RL), but trials at Limagrain have indicated it plays a more important role than first thought.

Liam Wilkinson, arable technical officer, explains: Stem health is really important because if you get a quick finish to harvest and the stem is damaged, it cuts off water and nutrient supply to the canopy and thats when you see oil losses and reduced pod formation.

Disease scoring In worst case scenarios, an unwell stem will kill plants off.

However, RL disease scoring is carried out based on foliar symptoms of diseases, disre garding stem symptoms.

In the field, diseased stems are often misdiagnosed as verticillium, despite the three main diseases in the UK being stem based.

Light leaf spot (LLS) is becoming ‘the yellow rust of oilseed rape, Mr Wilkinson says.

The disease can reduce yield by up to a tonne per hectare and exhibits two main symptoms, one of which is often missed.

There is the puckering of the leaf with cigar ash lesions, but its the stem-based symptoms causing problems that were starting to see more of here and on the continent.

LLS has been known as the Scottish disease, but last year it was picked up across the whole of the UK and in many parts of northern Europe.

Mr Wilkinson says: Its no longer confined to the North its endemic.

Were seeing different strains on crops, mainly fuelled by climate change, helping LLS to move into the polycyclic stage.

The multi-cycling disease splashes from leaves and spreads onto the stem, where in Europe it is known as cylindrosporium.

Ratings differences Work by Limagrain exploring whether there is a difference between LLS resistance ratings and stem health within the same varieties has unearthed some interesting results.

Mr Wilkinson says: All the varieties we looked at scored 7 for LLS but we saw visual differences in trials looking at the health of the stems, which matches similar data in France and Germany.

This is because the bulk of RL trials scores come from foliar symptoms.

This means varieties with poorer stem scores will die off quicker in stressful conditions or in seasons when crops senesce quickly.

In normal seasons you probably wont see much of a difference because weve got quite a long finishing period in the UK, but last season crops senesced quite quickly and thats where you see the yield differences in those early cut off harvests.

Newer varieties including Auckland and Aurelia per formed well in the stem-based scoring and LG now has extensive nurseries across the UK looking beyond what is on the RL for stem health.

Learning lessons from losses

Limagrains establishment scheme, which offers growers a £100/hectare refund if the crop does not establish before the end of October, has produced some useful data on getting the crop off to the best start.

The scheme covered 19,000 hectares of crops drilled with LG varieties in 2021, accounting for up to 8% of the total hybrid area.

It is estimated 5% of the national crop was lost last autumn.

According to LGs data, most crops were lost in the latter half of August.

Weather data for England across the same period highlights the close correlation between dry weather at drilling and when crops were lost.

This also coincided with the risk period for the start of flea beetle migration identified by ADAS.

LGs arable marketing manager Will Charlton says: This really just highlights to never drill by calendar date but drill to the conditions.

Vigour Choose a variety with vigour and adaptability to aid this.

With these very vigorous hybrids, if you havent got your wheat cleared by the end of August and its very dry, because of the vigour in those varieties, you can afford to leave it in the shed for a few weeks until there is rain on the horizon and those varieties will be able to catch up.

Seed sales reflected the move towards earlier drilling, with 60% of LGs sales done by the end of July.

Having the crop drilled earlier makes it easier to establish but you do need to consider larval damage in those situations, Mr Charlton adds.

You do not want a very thick crop if you want to minimise larval damage.

Rather than branching out, it just goes straight up and what youre trying to avoid is excessive amounts of larvae in the main stem.

Side branches arent an issue as a well branched plant can cope with a lot of larvae in the side branches, but not the main stem.

If youre growing wider row widths you may need to look at your overall seed rate because you may well be sowing much thicker within the row.

Autumn and spring PGRs will manage lodging risk but you need to manage the canopy within that.

Mr Charlton expects the oilseed rape area to creep up to 400,000ha for the 2022/23 crop, depending on the weather at planting, as growers slowly regain confidence in the crop.

He says: Anecdotally, those that have kept growing OSR now have a greater understanding of a strategy for their system that works to get a crop established through the main risk period.

Flea beetle pressure Genetics have also improved significantly and, potentially, with less crop there has been less flea beetle pressure.

Prices are very high and demand is fixed for OSR.

Trends for future prices were very buoyant even before the Ukraine crisis.

Moving into specialist markets

As well as stem health, Limagrain is also focusing its trait stacking into specialist varieties such as Clearfield and clubroot, which Mr Wilkinson says seems to be increasing in prevalence due to the greater number of brassica mixes in cover crops.

Clubroot is becoming a real problem.

We are drilling earlier into warmer, wetter soils and clubroot thrives in those conditions.

Although were establishing earlier to get the crop up and away, youre exposing it to more disease and putting the genetics under a lot of pressure.

Joining LG Anarion, a clubroot variety offering TuYV and pod shatter, the company is launching LG Scorpion this year as a clubroot stacked with LGs hallmark traits, TuYV, pod shatter (PoSh) and RLM7.

Responses Mr Wilkinson says: Scorpion has one of our best verticillium resistance responses and its very quick to establish in autumn.

Its the quickest variety we have in the portfolio so its not one for early drilling, meaning you can take some of the risk out of clubroot anyway by going slightly later, but you also have the insurance of a wider drilling window.

For those in the East or West its where Id be looking.

For growers in the North, LG Anarion has a light leaf spot score of 7 and winter hardiness, which makes it one of the most popular varieties in Poland.

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