OSR variety Quartz cuts risk of canker

The new oilseed rape variety Quartz could offer growers better control of phoma stem canker because of its high disease resistance, which will also help out in a wet autumn.


Many crops received no fungicide treatment last autumn, leaving the disease unchecked, and so a new, more resistant variety may well have a place when wet weather prevents fungicide treatment.


Speaking at a briefing for seed breeder KWS, Rothamsted plant pathologist Jonathan West highlighted that UK stem canker losses exceed £150m a season.


“Typically, you would see a 10% yield reduction, even with some fungicide programmes,” he said at the event held at Rothamsted Research in Hertfordshire.


The pathogen survives on plant debris from the previous crop, which then releases spores over several months in summer and autumn. Spores then land on to newly emerging plants, resulting in the characteristic leaf spotting.


During winter, the fungus grows along the leaf petiole and if it reaches the stem, it then results in a very damaging stem canker, causing lodging.


“Separating crops from last year’s debris can help prevent it, but this is difficult when growing rape in very tight rotations,” said Dr West.


The main defence is a one- or two-spray fungicide programme focused on the key October/November timing.


On well-established crops, the earliest leaves tend to fall off before the fungus reaches the stem and with later leaves, there is insufficient time for it to reach the stem and produce a damaging canker.


Backward crops are more likely to need a two-spray regime as they are more vulnerable.


So managing phoma may become easier with Quartz, which has the highest disease resistance rating on the HGCA East and West Recommended List of 9. It has already secured a market share of 4-5% this season.


This variety’s resistance is multi-gene, which means it is more robust. It has two major genes for resistance (RLM4 and RLM9) plus lots of minor-gene resistance.


The stem canker 9 rating means growers can concentrate on treating light leaf spot with peace of mind for phoma, said KWS ­product development manager John Miles.


Dr West believes that having a good background resistance helps growers manage the disease as it gives them a bigger window for treatment. “In addition, it could also mean one spray may suffice rather than two.”


Mr Miles added that growers could prioritise different crops. “They can create a priority list, treating more susceptible varieties with lower scores first.”


Finally, growing Quartz could eventually lead to less stem canker inoculum being produced, reducing overall levels in tighter rotations, said Mr Miles.


And stem canker resistance is not the only advantage. KWS oilseed rape product manager Tom Dummett highlighted that Quartz has a yield of 102%, only 1% behind the leading conventional and has a good oil content of 45.5%, helping growers secure an oil bonus. Being a lower biomass variety, it has a lower height of 146cm and is stiff stemmed.


Quartz also overwinters well and has shown good winter tolerance in two years of trials in Poland.




Second-placed Rivalda performs well across seasons



The second KWS conventional variety that made it onto the current recommended list this season offers all-out yield with good resistance to verticillium wilt.


Rivalda is a high-input, high- output variety, which has the top conventional gross output at 104%, on par with the best hybrid.


The oil content is not as high as Quartz at 44.7%, but it is stiff stemmed (7) and offers good lodging resistance (8). It has an average height (150cm), but Tom Dummett added that it does need its inputs with scores of just 5 for both light leaf spot and phoma stem canker.


The one key attribute highlighted by Mr Dummett is its consistency of performance across seasons. He believes this is due to its earlier flowering and later maturity.


“So no matter what the season throws at it, the longer pod fill and seed development period give it greater compensatory power, hence being less variable,” he said.


Rivalda offers good resistance to verticillium wilt, a disease that has gained greater attention in recent years. John Miles pointed to ADAS trials and NIAB TAG data, both showing Rivalda exhibiting good resistance.


In conclusion, Dr Jonathan West warned that tighter rotations were making soil-bourne diseases (such as verticillium wilt) more of an issue.


“The first season verticillium wilt really hit crops in the UK was 2007 and it is here to stay,” he said.


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