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Seed Research
Great Strides in Potato Research

by Dorothy Noble

In terms of farm cash receipts, potatoes are the top crop in the United States. Yet, potatoes are susceptible to a plethora of diseases and pests. Add environmental stresses to these difficulties, and it’s easy to comprehend the importance of potato research.

The Agricultural Research Service (ARS) of the U.S. Department of Agriculture in Aberdeen, Idaho, and Beltsville, Md., as well as a number of university researchers, cooperate in breeding programs to improve disease resistance, processing abilities, nutritional quality and to develop new varieties of potatoes. Industry organizations also play a part.

Area needs drive breeding

Because performance of a potato variety differs significantly among regions, breeding efforts often focus on the specific needs of an area. For example, internal heat necrosis remains more problematic in the South. The recent resurgences of late blight, plus the appearance of different strains, prompts intensive work for more research into this historically devastating disease. Pathogens such as the golden nematode are now being observed for the first time in some regions. Drought stress, too, often occurs in areas heretofore untroubled. As pests, including the Colorado potato beetle, become more resistant to pesticides, cultivar development to replace susceptible varieties gains importance. Increasingly, the need for reduced fungicide and fertilizer usage due to both environmental and cost considerations leads to more efforts in these directions.

Markets seek a variety of traits

Desirable potato attributes are particular to each market. Processors need potatoes with high specific gravity. This high solids content, with little water, absorbs less oil when fried. Chippers tend to value bright white, smaller potatoes that are low in sugar.

What is ideal for a fresh market tuber depends on the intended use. Those marketed as baking potatoes must possess high solids, or starch content, which produces the fluffy texture. These are frequently russets. Desirable boiling varieties are the opposite; they feature low solids. Finger-lings typically contain even lower starch components, which gives them the ability to hold their shape when boiled. The growing specialty segment attracts the colors: blue skin with bluish-purple flesh, red skin with yellow flesh and purple skin with purple or yellow flesh.

Responding to the need for versatility, the number of introductions of dual-purpose potatoes is increasing. These potatoes can be processed or marketed as table stock.

All the markets, even those where tubers are destined to be peeled and configured into frozen french fries, desire a potato with a pleasing appearance when whole.

Because most potatoes are stored, and the necessary low temperatures to deter rotting and sprouting convert starch to less desirable sugar, the industry seeks varieties that demonstrate slow conversion. Otherwise, the tubers must be reconditioned by controlled warmth.

In addition, the interest in enhanced health attributes creates demand for more varieties to capitalize on that trend. Also, improved flavor and lengthened dormancy require continuing research.

In short, potato breeding is a demanding, never-ending effort. Moreover, the length of time required to develop a new release is typically 12 to 15 years. Extensive trials in certain areas and the need to increase certified seed can extend this time. Fortunately, potato breeders quickly exchange their research data.

Russet potatoes dominate processing markets, including the frozen fries and dehydrated products. The Pacific Northwest, in general, with its climatic conditions and typical irrigated growing methods, produces superior russets. Consequently, researchers located in that region in particular continue to develop varieties that process well. Releases of the Northwest Potato Variety Develop-ment Program (NPVDP), concentrated in Idaho, Oregon and Washington, highlight the strides made in russet breeding.

New releases show improvements

The following introductions or recent releases of primarily processing potatoes were available by press time. New varieties of fresh market and specialty potatoes will be covered in a subsequent issue.

Beacon Chipper, released by Michigan State University, has little internal heat necrosis, but a moderate amount of scab. Round and fairly smooth, it is an attractive white tuber. During two trials in 2007, its yield was 97 percent of the standard chipping potato (Atlantic), with specific gravity 12 points lower. Its weaknesses include short dormancy and hollow heart.

Blazer Russet, an oblong dual-purpose developed by the NPVDP, has resistance to external defects, common and powdery scab and is moderately susceptible to the common strains of potato virus Y. The three-state Potato Variety Management Institute (PVMI) indicates it as an early replacement for Shepody. In the Idaho, Oregon and Washington trials, it produced 75 and 80 percent tubers grading U.S. #1.

A North Dakota release, Dakota Diamond is a large, round, late-maturing tuber. Compared to Atlantic, it yields as much, but with specific gravity 5 points higher. It has some scab resistance, but slightly less internal heat necrosis than Atlantic.

Highland Russet, released in 2006 by the NPVDP, produces long, lightly russeted tubers mid to late season. With a specific gravity similar to Russet Burbank, it out- yielded that standard in the three-state trials. A processing potato, it has moderate resistance to common and powdery scab, tuber late blight and the common strains of potato virus Y. It has moderate susceptibility to verticillium wilt, early and late foliar blight and soft rot.

Kalkaska (MSJ036-A) is being released by Michigan State and commercialized. A scab-resistant chipper, its pedigree includes chipper-processor low sugar lines.

Lehigh, from the Cornell program, demonstrates excellent resistance to common scab and to the golden nematode race Ro1. A dual-purpose potato released in 2007, Lehigh produces large tubers with moderately textured skin and yellow flesh with few internal defects. The specific gravity is slightly less than Atlantic, but Lehigh chips better than most yellow varieties. While the average tuber set is somewhat less than Atlantic, its average tuber weight is greater, and the dormancy is about two weeks longer. In addition, it excels as a table stock potato.

For both fresh and frying, NPVDP developed Premier Russet. Its excellent cold-sweetening resistance allows storage at colder temperatures to prolong tuber dormancy and assure quality processing or fresh pack use. A late-maturing variety, it demonstrates high yields and high grades, plus it has high specific gravity. In addition, it tolerates water stress. However, it has some susceptibility to black spot, dry rot and hollow heart early in the season. Premier Russet has moderate resistance to verticillium wilt, early blight and soft rot, and is resistant to the common strains of potato virus Y.

Yukon Gem, another NPVDP variety, is a dual-purpose, yellow potato with substantially higher yields than Yukon Gold, one of its parents. Yukon Gem provides excellent chip color. Plus, its post-harvest evaluations for the fresh market uses for boiling, baking and microwaving rank comparably to Yukon Gold. It also has Yukon Gold’s pink eyes. It is notable for its resistance to net necrosis, tuber late blight, pink rot and the common strains of potato virus Y. Yukon Gem also has moderate resistance to common scab, foliar late blight and dry rot. It is susceptible to verticillium wilt (although less so than Yukon Gold). The maturity is medium-early, and storage ability ranks medium.

The NPVDP plans to release dual-purpose A95109-1 in 2008. The PVMI says this is the best-tasting russet developed. It has early yields with a high percentage of #1 tubers. While not suitable for processing from long-term storage, it fries well from the field and following short-term storage. It resists common scab and dry rot and has moderate resistance to verticillium wilt, net necrosis and soft rot. As with almost all potato varieties, it has some susceptibility to potato virus Y and foliar late blight.

Two other russet varieties are being considered for release by the NPVDP. A9305-10 is a long, lightly russeted processing variety. It has few defects, high yields and grades and a long dormancy similar to that of Russet Burbank. It has resistance to common scab, white mold and moderate resistance to soft rot and verticillium wilt. It is susceptible to net necrosis, foliar and tuber late blight, potato virus Y, corky ringspot and is moderately susceptible to dry rot. A0A95154-1 produces a high percentage of #1 tubers with high specific gravity. With its long russet appearance, its uses include fresh market and frying, where it shows desirable color. It has shown internal brown spot in the southern Columbia Basin and some hollow heart. With the exception of potato virus Y and corky ringspot, this variety has shown moderate resistance to other diseases common to potatoes.

The author is a writer/researcher specializing in agriculture. She currently lives in central Pennsylvania.