Another Life: Here’s hoping it’s a good summer for potatoes

Michael Viney: Variability of Irish weather continues to pose late blight risks

Potato flowers. Illustration: Michael Viney

Potato flowers. Illustration: Michael Viney

 

“If you’ve grown enough potatoes for a year, what can they do to you, really?”

When this revelation first struck me I was leaning on my spade near the bottom of the acre, where a random hawthorn bush now flourishes. Spring had sprung, primroses gleamed below the ditch and a robin perched nearby, waiting for the next worm.

A similar glimmer of satisfaction, I like to think, may this month be stirring in some of the nation’s new lockdown potato gardeners, even if it’s only half the back lawn that’s been boldly furrowed for the crop.

Enough spuds for a year takes at least half a dozen mammoth lazy beds, 10 metres long, and an inordinate appetite for big, baked Records. They were a mainstay of our pioneer years in the west and digging the ridges broke ground on almost half the thistly acre.

Just before the Famine, the hillside was ridged from top to bottom. A last stretch of the grassed-over beds still corduroys the upper reaches, where rocky footings of the old cabins survive among the rushes. When blight arrived, late in the summer of 1845, the sweet smell from all the blackened haulms of Lumper potatoes must have enveloped the land.

Late blight is not, I discover, a true fungus but close to the oospores of a brown alga, and it “co-evolved with its potato and tomato hosts in the Toluca valley of Mexico”, reaching Europe with tubers shipped to Belgium from New York. Such is its history from Teagasc, now marking 175 years of Ireland’s dealings with Phytophthora infestans.

What emerges from its current research journal is a story not so different from Covid-19, in that the pathogen of late blight has continued to evolve and mutate, matching and outstripping the breeding of “resistant” varieties. After Lumper came the Scottish Champion and then Kerr’s Pink (this surviving today, big, creamy and floury if not actually pink inside and still a risky choice).

For decades of the 20th century, the potato fields of western Europe were blue with sprayed fungicide, the “Bordeaux mixture” based on copper sulphate. In Connacht, says folk history, it was flicked deftly across the ridges from bunches of heather. In Leinster, commercial growers are still spraying fungicides up to 10 times in the season, not always to safe effect.

Teagasc began breeding potatoes in the 1960s and two of its partially resistant varieties, Orla and Setanta, are widely grown organically. They’ve been joined by the pink-skinned Sarpo Mira, a variety developed originally with potatoes from unsprayed collective farms in communist Hungary.

Much promising work has screened wild relatives of the cultivated potato for blight-resistant genes. But stacking up the right defensive layers of genes can take decades, with genetic editing (GM) a tempting but still contentious alternative. No “significant” GM potato varieties, says Teagasc, have been released in the EU. Yet the EU’s new Farm to Fork strategy calls for a halving of pesticide use by 2030.

GM technology has prompted consumer resistance through its transfer of genes from one species to another. Teagasc researchers have been exploring the newer techniques of cisgenics, which transfers genes between the potato family or from other naturally hybridisable plants. This wins higher public approval but faces the grouping of cisgenics into Europe’s GM legislation.

With cisgenics, a novel potato can be engineered in a matter of weeks. One developed with EU funding and trialled initially in the blight-prone Netherlands was also sown for three seasons on Teagasc land at Oak Park, Co Carlow. It reduced fungicide spraying by 90 per cent, producing high yields without harm to soil organisms.

Cisgenic engineering

The speed of cisgenic engineering in editing genes is what enthuses the Teagasc researchers. “Late blight has a fantastic ability to rapidly evolve new strains,” says Ewan Mullins, its head of crop science, “and this arms race between plant and disease is continuous.”

It reached a peak of aggression in the mid-2000s with the arrival of a strain of blight labelled Blue-13. This launches waves of genotypes resistant to the most widely used systemic fungicides. Potato growers have responded by stepping up the intensity of their sprays.

“Given the variability of the Irish weather,” concludes Dr Mullins, “the risks posed by late blight to Irish potato production continue to be immense.”

On our hillside, swept by clean sea winds, I grew many bags of potatoes for years, switching to resistant Sarpo breeds as these came along. And yes I might spray once, if blight weather got too worrying.

This year, I’ve sown enough for a few months of eating spuds in their skins – these in the polytunnel, a hopefully spray-free quarantine. To potato gardeners back in Dublin, I wish an impeccably bright and breezy summer.

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