Potatoes and sweet potatoes can be a genetic challenge

It’s time to cut and plant those spuds. Potatoes (Solanum tuberosum) are different than most vegetables we eat. They aren’t propagated by seed. Plants are grown asexually, meaning they are clones. All plants in a field are genetically identical to each other. Sweet potatoes (Ipomoea batatas) are propagated slightly differently, but they are still asexually reproduced.

Few people would even give this a second thought, but it creates a potentially catastrophic situation when it comes to disease control. Large scale operators are aware of this and pay close attention to weather that could cause a suitable environment for certain disease organisms.

Favorable environment, susceptible host and virulent pathogen are the three corners of the disease triangle. Should any be absent, a disease would not occur.

Enter the potato. Should conditions be right for a disease to develop all plants in a field could be attacked. Late blight is a common potato pathogen.

Inoculation is at its peak under moist conditions and night temperatures between 50 and 55 degrees. Should late blight spores land on dew soaked susceptible leaves under these conditions, disease will spread. The Irish Potato Famine was a great example of this.

That’s why farmers must spray to control these problems. Regular fungicide sprays will control fungus diseases like late and early blights. Insecticide treatments to kill insects that carry viruses is also critical.

Planting resistant varieties is also another strategy. The problem is that market demands certain eating qualities of the crop. Avoiding disease is fine, but if proper specific gravity and other factors aren’t right, the final product may not be what the public wants.

For most seed propagated crops there is a certain degree of genetic variation. Self-pollinated crops like wheat are an exception. Back in the 1930s black stem rust of wheat consistently decimated wheat crops. Plant breeders developed resistant varieties to eradicate the disease, but it wasn’t easy.

Fruit trees are reproduced by grafting, so lack of genetic diversity is a problem too. It’s not like the Johnny Appleseed days when a broad genetic base of seedlings hedged against total crop failure.

Certain pear varieties can’t be grown in the eastern states because of a bacteria disease called fire blight. It’s rarely cost effective to chemically control bacteria diseases in plants. This is largely due to the speed that bacteria reproduce and adapt.

Overcoming disease pathogens that constantly adapt to our systems of crop managements provides more than enough challenges to crop breeders and plant pathologists. Add to that quality factors that the public demands, and the job is even more daunting.

Different geographic regions pose different challenges. As far as potatoes in eastern North Carolina are concerned, a potential selection characteristic is resistance to cold waterlogged soils. Weather can suddenly turn hot and dry and those conditions aren’t great for growing spuds either.

It’s somewhat true for growing anything. However, when raising clonal crops like potatoes and sweet potatoes, experience is the best teacher. Farmers and gardeners become familiar with strengths and weaknesses of certain cultivars. They can predict the best course of action when problems arise. Right now, prepare for muddy fields or wait.


Ted Manzer teaches agriculture at Northeastern High School (tmanzer@ecpps.k12.nc.us).

About tedmanzer

I grew up in Old Town Maine and got a B.S. at the University of Maine in Plant Sciences/ minor in Botany. From there I moved to West Virginia and earned a M.S. in Agronomy at WVU. I also met my wife there. She grew up in rural WV as the daughter of tenant farmers who raised cattle and hogs. Their lifestyle at times was one of subsistence and I learned a lot from them. I've always been a foraging buff, but combining my formal botanical knowledge with their practical 'Foxfire-type' background opened up my eyes a little more. I recently retired from teaching high school agriculture after 25 years teaching with my wife. Until recently I wrote a weekly nature/foraging column for the local paper (dailyadvance.com). I also have written several Christian nature/adventure novels that can be purchased on Amazon in Kindle format. One is a five book family saga I call the 'Forgotten Virtues' series. In the first book, Never Alone (presently out of print), a young boy comes of age after his father dies in a plane crash, and he has to make it alone. The second book, Strange Courage, takes Carl from his High School graduation to his recovery from a nasty divorce. The third book, Second Chances, takes Carl from his ex-wife's death and the custody of his son to his heroic death at age 59. The fourth book, Promises Kept, depicts how his grandchildren react and adjust to his death (this one is not yet published). In the final book, Grandfather's Way, his youngest and most timid granddaughter emerges from the shadow of her overachieving family and accomplishes more in four months than most do in a lifetime. I use many foraging references with a lot of the plants I profile in these articles in those books. I also wrote a romance novel titled Virginia. It is available on Amazon and is a different type of romance from a man's perspective.
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1 Response to Potatoes and sweet potatoes can be a genetic challenge

  1. tonytomeo says:

    Monoculture is nice in landscaping, particularly with uniform street trees, but like you describe, can have disastrous results. So many trees that happen to be the same age can also be a problem if they start to die at a particular age. The palms of palm lined streets are not genetically identical, but will all start to die at about the same age anyway.

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