Knowing Your Roots

Posts tagged ‘potato’

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: or the Wisconsin Seed Potato Improvement Association (

Why would you want to X-ray a potato?

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When you think about how to use new advances in X-ray technology, potato breeding is probably not the first thing that springs to mind. However, scientific researchers at the University of Wisconsin are doing just that to help develop new potato varieties — and to do it faster!  State-of-the art, high- speed X-ray technology is now becoming a routine practice for evaluating potential new potato varieties, because it is faster and much more effective.  Do you remember your last X-ray at the doctor office? It was time-consuming, uncomfortable and expensive.  Not so with potatoes! Every day during harvest, tens of thousands of potatoes are examined in just milliseconds, at virtually no cost!

This technology is possible by incorporating a high speed X-ray imager into the potato-grading line (where potatoes are evaluated after harvest).  This imager takes an X-ray image of each tuber as it passes through the machine at a high rate of speed.  From that image,  computers calculate just about anything that you ever wanted to know about that tuber, including its weight, length, width, height and shape; most remarkably, it can determine if there are defects on the outside and even the inside of the tuber. This is a huge improvement on previous technology in both speed and expense, which is akin to doctors being able to take the X-rays they need as you drive past the clinic!   (more…)

Behind the Scenes: Potato Late Blight, There’s Blight on the Wisconsin Landscape!

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Late blight caused the Irish potato famine in the 1840s and 1850s.

This disease and its related problems caused massive hunger, starvation and poverty, resulting in mass emigration from the region.  This disease is still a concern today.

The fungus which caused the Irish potato famine is still active today.  It was identified in Portage County just last week.  It can cause serious problems for potato, tomato, eggplants and other solanaceous crops today.  Phytophthora infestans (“infests”) is the cause of potato late blight.  It is a fast moving, community disease that growers, home gardeners and garden center managers must take seriously and properly manage to ensure a healthy, adequate food supply.

There are many concerns for Wisconsin vegetable growers every year whether farmer or home gardener.  Weather, growth problems, pests, water, market demand—but one pest problem, foliar or leaf blight, is especially challenging.  This can commonly attack tomatoes, potatoes, carrots and cucumbers.  These diseases cause perfectly healthy appearing green plants to break out in brown spots, turn yellow and die prematurely.  Many home gardeners run to their local garden center for a remedy.  But by the time leaves begin to yellow and the brown spots appear the disease may have progressed to a point where there is no stopping it.

On the farm, vegetable growers face the same threat from foliar blights every year.  Potato and vegetable growers in Wisconsin have worked closely with University of Wisconsin researchers for decades, to understand the science behind that makes these blights tick.  Through research, we have developed and implemented innovative disease management strategies to both avoid and combat plant disease problems.    (more…)

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