A side of fries, hold the fungicide?

[Featured image: http://agriculture.by/blog/photo/igrushki-iz-kartoshki ]

By sometime next fall, your side of fries might contain potatoes engineered to resist late blight: the fungus-like disease (caused by Phytophthora infestans) that can cause a once-healthy field to rot in the ground. But rather than turning up our noses at a genetically modified organism, we may want to consider the benefits of blight resistant potatoes in particular. For growers, disease resistant potatoes could mean reduced applications of some of the most toxic pesticides. And unlike other genetically modified plants, these potatoes would not contain genes plucked from the genome of a different species. While these particular potatoes developed by J.R. Simplot (with more options possibly becoming available through other sources) also resist browning — a more mundane issue — late blight is nasty.

LateBlight12The blight not only infects potatoes, but related species like tomatoes as well. Some of you may recall the summer of 2014, when the disease jumped from one farm and garden to another along the east coast, killing tomatoes on the vine. Rows of once lush plants resembled vegetative versions of Zombie armies; upright stalks studded with browned blight infested leaves. Large brown spots blossomed on the fruits turning them soft and unsellable. But that wasn’t the first time that late blight went pandemic. Over a century ago a mysterious potato disease spread across Europe like wild fire. Healthy plants died within days. Potatoes in the ground turned putrid. Widespread starvation caused by massive crop losses allied with typhus, cholera and other diseases, worked in the Grim Reaper’s favor. Some one million Irish died and more than a million sailed for distant shores. Blight had made its way to Europe (by way of the New World, where potatoes too, originated) touching off the infamous Potato Famine.  Since its emergence on potato fields blight has remained the bane of farmers around the globe.

Of the destruction, James Mahoney, sent to document the event wrote: “I can now, with perfect confidence, say that neither pen nor pencil ever could portray the miser[y] and horror, at this moment, to be witnessed in Skibbereen…there I saw the dying, the living, and the dead, lying indiscriminately upon the same floor, without anything between them and the cold earth, save a few miserable rags upon them…not a single house out of 500 could boast of being free from death and fever.” 220px-skibbereen_by_james_mahony_1847

Blight is one of the most destructive agricultural pathogens, causing havoc for both small-scale organic growers and large-scale growers around the world from U.S. to Europe and Africa. It is a multi-billion dollars disease. Cornell plant pathologist William Fry has been tracking blight for decades and says there is a huge amount of fungicide used on potato production throughout the world, including the U.S. Depending on conditions says Fry, growers make anywhere from 6 to 18 applications a year.  Even organic growers resort to copper – a “natural” fungicide. “As long as blight is around with the given cultures that we have,” says Fry, “we have to use fungicide.” A decade ago approximately 2000 tons of fungicide was applied to potatoes in the U.S. alone. Aside from heightened vigilance (growers can now report and track blight), new cultural techniques and some forays into biological solutions chemical treatments continue; mantrozeb, chlorothananil, copper and others. While these chemicals may not end up on our plates they are toxic to applicators, and some are toxic to soil microbes. In response to repeated applications blight strains evolve resistance, playing into a vicious cycle of infection, treatment, resistance and more treatment.  Our changing climate only plays to the favor of fungi- and fungi-like pests like late blight. Growers are desperate for that silver-bullet treatment. But there is another way. A way reduce the need for treatment is to grow disease resistant potatoes.

Adapted from Natural Defense (available June 2017). For more about nontransgenic engineered potatoes read about the work of Jack Vossen and colleagues Wageningen Institute and their efforts to thwart corporate control of disease resistant potatoes in Natural Defense .

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