Like humans, potatoes develop scabs. Although they look similar – raised, rough, brown growth on the surface of the skin – they are fundamentally different. The scabs you got when you scraped your knee as a child are part of the human body’s natural healing process. When the scab finally falls away, new, unblemished skin is left underneath. In contrast, potato scabs are a disease that infect the tuber skin; these scabs don’t heal and can even get worse as the disease progresses. A better name would be “potato ulcers.” Ulcers are open wounds that are slow to heal, originally thought to be caused by factors such as stress or skin irritation but later, were shown to actually be caused by bacteria.
Potato common scab is caused mainly by the bacterium Streptomyces scabies. The scabs produced by these bacteria are largely cosmetic and limited to the surface of tubers, but they drastically reduce marketability and are rated as one of the top 5 potato diseases in the U.S. Common methods of controlling infection – using pesticides and increasing irrigation – are expensive and often ineffective. In organic production, scab can be the major cause of tuber rejection. This is a classic example where breeding a potato with natural immunity to common scab is the most effective and perhaps the only realistic approach to managing this serious disease threat. There are currently no varieties of cultivated potato that are immune to common scab, but wild potato species offer a wealth of genetic diversity and have long been viewed as a potential source of desired traits such as disease resistance. Researchers at the UW-Madison have identified a line of the wild potato species Solanum chacoense from South America that is highly resistant to common scab and a closely related line that is susceptible. (more…)
Go to your supermarket these days and you will see an emerging trend in the fruit and vegetable section – an increasing array of varieties on display that are specifically designed to meet consumer demands. Apples lead the way with dozens of different varieties on display with specific tastes, textures and uses. Other food favorites are jumping on the apple bandwagon with potatoes now joining the chase. Five years ago your potato choices were likely to be limited to russets, round whites and reds, served up in small or large bags with cost often being the a prime driver. Now, potato choices have rapidly changed as new varieties with multiple colors, shapes and sizes are part of the consumer’s palate. Today’s consumers are looking for specific varieties based on how they taste and whether they are using them for fries, chips, baked, mashed or salads.
The evolution of choice in potatoes is moving fast now but it has taken generations of painstaking and exacting science to get to where we are today. Over the coming weeks, the New Family Farm site will explore the art and science of breeding potatoes through the work of graduate students. Since the beginning of agriculture, humans have been identifying, creating and refining new varieties of food plants for their productivity, appearance and culinary characteristics. This process, known as plant breeding, continues to help improve potatoes to meet the evolving needs of society by bringing together the skills of several disciplines such as genetics, molecular biology, plant pathology, engineering and others.
The first step in plant breeding is to create individuals with novel genetics that may express the traits we are seeking. Just as humans create children by combining their genetic makeups, potatoes can be enhanced through genetics. Most new potato varieties are created by “mating” or cross pollinating existing varieties with other varieties, or ancestors, with the goal of combining the best characteristics of the parents to create a new potato that has the features we desire. Those green, tomato-like fruits, formed on pollinated potato plants contain hundreds of seeds, each one genetically distinct. It takes the artistry of the breeders to grow these thousands upon thousands of seeds in the greenhouse, identify the traits they express, select the most promising, re-cross to obtain the best balance and ultimately propagate them in the field. It can take years to develop a promising new potential variety. (more…)