Sustainable stem canker resistance

OSR VARIETY news Sustainable stem canker resistance

New traits coming to the market bring advances in disease resistance and nitrogen use efficiency in winter oilseed rape.

Anew source of resistance to phoma stem canker, labelled RlmS, will confer effective and sustainable resistance to the disease, says plant breeder LS Plant Breeding (LSPB).

The company is introducing RlmS to the UK market in two varieties: Respect and Flemming.

Respect is a hybrid set to become a new benchmark for plant health and yield stability, says LSPB. Along with its resistance to phoma stem canker, it is also said to have a high, consistent yield performance and vigorous growth habit in autumn and spring regrowth. The variety was added to the AHDB Recommended List (RL) for the East/West region for 2021/22.

Flemming is another first for the UK market as a next generation hybrid with stacked traits, adding turnip yellows virus resistance (TuYV) to the RlmS resistance. A RL candidate variety, it is due to be considered for addition to the RL this autumn. Flemming promises the same yield performance and autumn vigour as Respect with a more prostrate growth habit, says LSPB.

Chris Guest, LSPB managing director, explains the innovations behind RlmS.

“This gene was identified by breeders at NPZ, LSPB’s shareholder, who have been researching phoma resistances for decades. It was integrated into our breeding programmes and developed into a viable trait for commercial varieties.

Genetics

“It is important to note that the RlmS gene is distinct from those widely found in current oilseed rape varieties. Hence, by developing our hybrids with different genetics, we give extended and resilient phoma resistance in the field.

“The unique phoma resistance is also associated with strong overall plant health and the gene has especially good stem resistance that brings better protection against the increasingly important pathogens of verticillium and sclerotinia.

“While cabbage stem flea beetle is seen as the major current threat by growers, it should be emphasised that stem canker/phoma is one of the most important diseases in oilseed rape that has widespread and regular occurrence, taking up to 50% off yield potential. It is estimated that total economic losses from the disease reach about £100 million each season.

“The oilseed rape area is set to rebound to sustainable levels this autumn as, by most measures, it is the best break crop on a gross margin basis. The heightened resistance from our new varieties to stem canker/phoma – and added TuYV resistance – will be an important weapon in the armoury of growers.”

Other winter OSR varieties to have emerged from the LSPB breeding programme in recent years have included clubrootresistant varieties Croozer and Crome, plus the HEAR variety Resort, which are all currently on the Recommended List.

“Respect and Flemming are a new and exciting generation of hybrids,” concludes Mr Guest.

The RlmS gene in the LSPB varieties Respect and Flemming brings a new source of phoma resistance to the market.

Strength in four-trait varieties

JThe high yielding hybrid oilseed rape LG Antigua offers the N-Flex trait, which makes it a four-trait loaded variety encompassing TuYV, pod shatter, RLM7 phoma resistance and now N-Flex, says breeder Limagrain.

Varieties with the N-Flex trait have the ability to use nitrogen more efficiently. In the field, this means varieties with the trait are better able to withstand delayed or sub-optimal nitrogen applications.

This has been confirmed in trials over the last few seasons in Europe, testing LG Antigua’s performance in optimal and sub-optimal nitrogen conditions.

Will Charlton, Limagrain UK arable marketing manager, says: “Essentially the N-Flex trait means hybrids containing the trait use each unit of available N more efficiently than those which don’t. In the field, this translates into varieties with the trait producing more stable yields year to year, with less in-field yield variability.”

Comparison of four-trait varieties

Source: Limagrain

LG Antigua LG Aviron Ambassador

Gross output UK 108 108 108 Gross output E/W 109 109 109 N-Flex Y Y Y Pod shatter Y Y Y TuYV Y Y Y RLM7 Y Y Y

The addition of the N-Flex trait illustrates Limagrain’s approach to producing trait-loaded hybrid oilseed rape varieties, adds Mr Charlton.

Pod shatter

High yielding varieties Ambassador and LG Aviron were the first four-trait loaded varieties, offering genetic resistance to TuYV, pod shatter, RLM7 and the N-Flex trait. LG Antigua now joins this line-up.

Split field trials are being carried out on commercial farms this season to evaluate how N-Flex aids spring nitrogen management and secures yields, Mr Charlton says.

Breakthrough sclerotinia tolerance trait

JThe first winter oilseed rape variety with a claim for tolerance to the stem disease sclerotinia has recently been launched by Pioneer, the seed brand of Corteva Agriscience.

The Pioneer Protector Sclerotinia PT303 hybrid has gained National Listing and the results from the independent AHDB Candidate List trials have been published.

PT303 has delivered the highest gross output yields in each AHDB region – including a UK region yield of 111%.

It was ranked first with a gross output yield of 116% in the East/West region and also topped the North region with a yield of 105%.

PT303 also delivers turnip yellows virus and RLM7-based phoma resistance.

In Corteva trials with sclerotinia infection levels at 25% or above, the severity of the disease was reduced by up to 75%. Trials also showed the higher the severity of disease, the greater the benefit from the trait.

Corteva Agriscience seeds and inoculants sales manager Andy Stainthorpe says: “Pioneer Protector Sclerotinia PT303 gives farmers the ability to reduce the incidence of disease and manage their crop protection applications with greater flexibility and assurance.

“With environmental effects such as global warming, sclerotinia is becoming a bigger burden for farmers during increasingly humid and wet weather.

“As domestic agricultural policy evolves and farm businesses pursue a more efficient, productive future, PT303’s potential to limit the development of sclerotinia could be a significant component of disease control strategies.

“Sclerotinia only strikes every so often, but when it does it is hugely damaging to yield.

“Having identified a genetic source of sclerotinia tolerance, Corteva breeders have spent more than a decade crossing that source into our regular hybrids through traditional breeding.

Milestone

“No products have previously offered any level of resistance to sclerotinia but with PT303 we now have a variety that has tolerance – a major milestone in our industry.”

PT303 scores 6 for light leaf spot resistance and 7 for stem canker in AHDB trials and has proven turnip yellows virus resistance, adding an extra layer of protection for growers.

Sclerotinia levels were 75% lower in PT303 than in susceptible varieties in trials where infection levels were 25% or above, says Corteva.