Knowing Your Roots

Posts tagged ‘disease’

Fighting the rotten potato – Is the answer hiding in its ancestors?

New Family Farm Updated PictureIt’s dinner time, and you open your cabinet to reach for the sack of potatoes. As you begin to imagine the smooth and creamy texture of your famous mashed potatoes, you realize your hand has landed in a pool of slimy rotten goo with a foul odor you never thought imaginable. As a consumer, this is aggravating, and you wonder what caused it and who to blame. Unfortunately, this rot can be everywhere in the environment from the soil to the storage sheds and even in the grocery store. Farmers and food distributors are very aware that the cause of the foul potatoes is a disease called soft rot, which can be caused by a handful of bacterial pathogens. One of the most common of these is Pectobacterium carotovorum, which is often the reason your potatoes looked healthy at the grocery store and later became rotten. This is an annoyance in your kitchen, but it can be a catastrophe to the farmer when that rot occurs in the middle of a 55 semi-load pile of tubers in a storage bin. This is a seemingly cunning process that begins innocuously in the presence of moisture, which allows bacterial cells to penetrate the potato. When small numbers of bacterial cells enter, they lay hidden from the plant’s defense system. While hidden, they release signaling molecules into their environment. As the population grows, the signaling molecules accumulate, and the individual bacterial cells are able to sense when the population is large enough to overtake the plant’s defenses. When this occurs, the bacteria release enzymes that break down the plant’s cellular walls, resulting in the contents of the plant cell spilling out and becoming available to the bacteria—a.k.a. the rapidly spreading pool of slime you reached into!

  1. carotovorum has the widest host range of the soft rotting bacteria, including lettuce, carrot, broccoli, onions, tulips, irises and sunflowers, to name a few. This means that it affects not only farmers across the world but also home gardeners. The loss that results from vegetables affected by soft rot represents an accumulation of losses from the labor, land, water and economic resources that were put into growing the crop throughout the season. There are very few options for chemical control of the disease, and the best available practices are planting disease free tubers from reputable sources (like the Wisconsin Seed Potato Improvement Association), sanitizing tools and machinery to keep them free of bacteria and quickly disposing of plants that become infected.

Planting varieties that are resistant to soft rot would be the ultimate solution, but unfortunately, there are no varieties on the market that can tolerate infection, even though there are wild ancestors of potato that have developed a natural resistance over time. In my research I have challenged geographically diverse potatoes from the wild ancestor, Solanum chacoense, using soft rotting bacterial cells tagged with a fluorescent protein that allows infections to be visualized and dramatically monitored. This technique has enabled us to identify varying degrees of tolerance to soft rot, including a promising inbred line able to tolerate infection by 2 of 6 strains of soft rot, including common strains. When crossed with susceptible cultivated potato varieties and challenged with labeled soft rot in the field, all progeny became infected, but bacterial cells in offspring of the tolerant inbred line declined more quickly.  This demonstrates that soft rot tolerance is present in wild potato and may be heritable is a promising development. These wild potatoes can be used in breeding new varieties that are able to overcome soft rot infection and can also be used to determine the genes that are responsible. Once these genes are found, breeding soft-rot tolerance into popular cultivated potatoes will be more efficient. This process represents the critical first step in generating soft-rot tolerant plantlets that can then be used to produce the mini-tubers that will ultimately become the certified seed that is distributed to potato growers across the US.

So the next time you encounter a bag of rotting potatoes, the smell may be just as disgusting, but you can now appreciate the painstaking work of the scientists who are determined to thwart this pernicious threat. You can rest assured there is someone working hard to prevent your dinner being ruined!  For more information contact Jenna Lind: jennamarie.lind@gmail.com or the Wisconsin Seed Potato Improvement Association (http://www.potatoseed.org/)

What makes a potato beautiful?

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Today’s potatoes suffer from lowered self-esteem due to constant bombardment from the media’s perception of the “ideal potato.”  This phenomenon first emerged in 1952 with the debut of Mr. Potato Head.  Here was the plastic representation of what a potato was supposed to look like — only two eyes, smooth, unblemished skin and that perfect oblong shape that was designed to be baked and filled with goodies. No mention of the myriad of nasty diseases that are likely to attack a real potato during its life. In recent years, this popularized image has only gained traction due to Mr. Potato Head’s breakout role in the box office hit “Toy Story.” This media exposure is sending a message to our potato youth that in order to be beautiful they should ignore life’s realities and emulate a plastic toy.

But help is on the way! Scientists in the University of Wisconsin potato breeding programs are working hard to help young tubers grow-up in the field to reach the size, shape and taste that consumers want, without succumbing to all those nasty diseases. In our lab, we are employing advanced techniques that enable potato varieties (already accepted in the marketplace) to have all the qualities that consumers want and resist infection from diseases without the need for grower intervention. In my project, I am working with one of the most widespread and destructive diseases of potatoes, aptly named early dying. This disease is caused by a fungus called Verticillium that attacks through the roots and clogs the plant stems causing them to wilt and die prematurely. The fungus persists in soil for multiple years and growers have few options other than fumigation or extending the time between potatoes to multiple years, which are both hard on the pocketbook!   (more…)

Thoughts for Food: The Leafhoppers are Coming!

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It’s the growing season in the Central Sands and a new crop is emerging; carrots are peeking up amid the oats, a “nurse crop” that is used to protect the delicate young carrot seedlings from damaging winds and all of us have an expectation for another great crop.  Although most Wisconsin farmers are keeping an eye on the carrots, they are also concerned with what’s happening in southwest Arkansas.  Why? (more…)

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