Net Necrosis Research Articles

The relation of potato leaf roll virus net necrosis in potato tubers to the interval between planting and inoculation

The green peach aphid, Myzus persicae, is a vector of potato leaf roll virus. Inoculated potato plants may develop tubers expressing net necrosis at harvest or in storage, which can significantly reduce the crop's commercial value. Insecticides have been traditionally used in a prophylactic manner to suppress the aphid population in the field thereby preventing inoculation and the advent of net necrosis. To analyze the rationale of such an insecticide application decision, data generated by two field experiments were used to establish an empirical relationship between the probability that a tuber will express net necrosis (NN probability) and the time after planting that inoculation occurs (inoculation interval). In contrast to past studies, the data analyzed here allow for the investigation of the impact of inoculation dates occurring over the entire growing season. This uncovers the previously unknown empirical result that NN probabilities may peak before monotonically declining in the second half of the growing season. It implies that insecticide spraying might profitably be concentrated on inoculation intervals generating peak probabilities, to ‘flatten’ the peaks to acceptable probability levels. The data also permitted a limited analysis of the systematic ways that increasing storage periods may alter the empirical relationship between NN probabilities and inoculation intervals.

Mainestay: A high-yielding, round white potato variety for fresh market

The Mainestay potato variety is high-yielding and late-maturing producing attractive, round, white-skinned, white-fleshed tubers with medium-shallow eyes. Its major use is expected to be as a maincrop tablestock variety. Mainestay appearance ratings are similar to those of Katahdin, and greening in Mainestay tubers is less than in Kennebec. Most boil and bake qualities were rated equal to Katahdin in at least half of the tests, and Mainestay usually has a low incidence of internal defects. However, purple streak, heat necrosis, vascular discoloration, and heat sprouts have been seen on occasion. Mainestay tubers do not show the net necrosis caused by potato leafroll virus, and have shown very little hollow heart or blackspot bruising. Mainestay is susceptible to common scab and acid scab, but moderately resistant to verticillium wilt (Verticillium, albo-atrum andV. dahliae), early blight (Alternaria solani), rhizoctonia (Rhizoctonia solani), dry rot (Fusarium sambucinum), and pink rot (Phytophthora erythroseptica). It is moderately susceptible to the common race of late blight (Phytophthora infestans). Mainestay tubers are slow to mature after vine kill, and additional time is required prior to harvest in order to allow for proper periderm development and to reduce storage losses.

St. Johns: A round white potato variety for fresh market

The St. Johns potato variety is high-yielding and late-maturing with attractive, round to oblong, white-skinned, white-fleshed tubers with mediumshallow eyes. Its major use is expected to be as a maincrop tablestock variety. Taste panels rated St. Johns better than or equal to Katahdin in texture, color, mealiness, and flavor. St. Johns tubers do not show the net necrosis caused by potato leafroll virus, and are resistant to golden nematode, corky ringspot, hollow heart, and blackspot bruising. St. Johns is also moderately resistant to greening, shatter bruise, verticillium wilt, early blight, common scab, the common race of late blight, leafroll,Fusarium sambucinum (dry rot) andErwinia carotovora (soft rot), although some breakdown has been reported in commercial storages. Symptoms of leafroll virus infection are somewhat difficult to detect.

Portage: A new early-maturing, round white table potato variety

The Portage potato variety is high-yielding and early-maturing with attractive, round to oblong, white-skinned, white-fleshed tubers with medium-shallow eyes. Its major use is expected to be as an early tablestock variety in areas where Superior suffers yield reductions caused by verticillium wilt. Portage tubers do not show the net necrosis caused by potato leafroll virus, and are susceptible to skinning, but are fairly resistant to hollow heart, blackspot and shatter bruise. Portage is moderately resistant toVerticillium alboatrum, andRhizoctonia solani, but its seed-pieces are sensitive to dry soil conditions; therefore, cut seed should be suberized before planting. Symptoms of leafroll virus infection are difficult to recognize.

Mainechip: A new chipping potato variety for cool storage processing

TheMaineChip potato variety is medium-maturing and has round, whiteskinned, white-fleshed tubers with shallow eyes, high specific gravity and moderate yields. Its major use is expected to be as a storage chipping variety since sugar build-up in storage is slow, and reconditioning is possible. This variety can be chipped directly from 7 C storage.MaineChip does not show the net necrosis caused by potato leafroll virus and is moderately tolerant to verticillium wilt (Verticillium alboatrum) and rhizoctonia (Rhizoctonia solani). It is also moderately resistant to blackspot and shatter bruise. Hollow heart is its major internal quality defect, being a problem in ten of the twenty-nine regional tests conducted over five years.

Prestile: A new round white potato variety

Prestile is a late maturing potato variety with attractive, round to oblong, white-skinned, white-fleshed tubers with shallow eyes. Its major use is expected to be for tablestock in areas where Katahdin and Ontario are now grown. Prestile tubers are slow to sprout in storage and do not show the net necrosis caused by potato leafroll virus, but are quite susceptible to heat necrosis. This variety is immune to potato virus X, and is moderately resistant to common scab (Streptomyces scabies), verticillium wilt (Verticillium albo-atrum), and early blight (Alternaria solani). Prestile is susceptible to skinning and shatter bruise, and is difficult to kill, particularly when heavily fertilized.

Ranger Russet: A long Russet potato variety for processing and fresh market with improved quality, disease resistance, and yield

Ranger Russet, a new full-season potato variety, was jointly released to growers by the U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Oregon, Washington, and Colorado on May 14, 1991. Ranger Russet was tested in irrigated performance trials in the Western U.S. since 1979. It produces a large yield of high quality, long, russet-skinned tubers that are well suited for baking and processing into french fries. Ranger Russet is more resistant than Russet Burbank to Verticillium wilt, viruses X and Y, leafroll net necrosis, and Fusarium dry rot. It is highly resistant to hollow heart.

Russet Nugget: A fresh market and processing potato cultivar with resistance to common scab

Russet Nugget is an oblong, smooth, high yielding potato with fresh market and processing qualities. It emerges quickly, produces an erect, large, vigorous vine with a profusion of white flowers, and is late maturing. Russet Nugget is very resistant to common scab, and moderately resistant to leafroll net necrosis,Vertcillium wilt, and early blight (tuber and foliage). In the San Luis Valley of Colorado, yield of Russet Nugget is comparable to Russet Burbank, with a significantly greater percentage of U.S. No. 1 tubers. In Texas, total yield is comparable to Norgold 40, with a slightly lower percentage of U.S. No. 1 tubers. Tubers of Russet Nugget have high specific gravity and vitamin C content.

Somerset: A new chipping potato variety

The Somerset potato variety is a medium-maturing variety with attractive, round to oblong, white-skinned, white-fleshed tubers with shallow eyes. Its major use is expected to be as a chipping variety in areas where potatoes are stored for some length of time, since its sugar content is lower than most varieties during storage, and it can be chipped after six months in storage. Somerset does not show the net necrosis caused by potato leafroll virus, and is immune to race 0 of Phytophthora infestans (late blight). Somerset is also moderately resistant to infection by Alternaria solani (early blight), and is only moderately susceptible to Verticillium wilt. Somerset is more susceptible to both common and acid scab than Superior, but less susceptible than Kennebec and Katahdin. It also has shown susceptibility to skinning and shatter bruise, but does not have a strong blackspot bruise reaction.

NemaRus: A golden nematode resistant, russet-skin potato variety

NemaRus, a russet-skinned potato variety resistant to race A of the golden nematode (Globodera rostochiensis), is medium-late in maturity (110 days) and adapted primarily to the Northeastern United States and Northern Florida. Tubers are oblong to long with moderately shallow eyes, and medium-to-heavy russeted skin. The specific gravity of NemaRus is similar to the popular Western U.S.A. fresh market russet variety Centennial Russet. Flesh is creamy white. Glycoalkaloid content of NemaRus averages about 12.0 mg/100 g fresh tissue. NemaRus is field-immune to the common strains of potato virus X and to tuber net necrosis caused by late current-season infection by the potato leaf roll virus. It is resistant to race O ofPhytophthora infestans to tuber rot caused byFusarium sambucinum & F. coeruleum; tolerant to scab, Verticillium wilt, and the pinkeye bacterial disease complex. It is also highly resistant to internal tuber net necrosis associated with high temperatures during tuber initiation and enlargement. NemaRus yielded 24% more U.S. No. 1 tubers than BelRus in Maine and 22% more than Centennial Russet in Northern Florida.

Coastal Russet: a mid-season Russet-skinned potato cultivar

Coastal Russet (tested as B9596-2) is a clone with mid-season maturity that produces russet skin tubers that are long and slightly flattened. Tuber yields in the eastern portions of the United States have been considerably greater than for BelRus. Tubers are well-shaped, have shallow eyes, and are attractive in appearance. Tuber appearance and size make this cultivar very well suited for the tablestock market. It is not suitable for processing. Coastal Russet is highly resistant to tuber net necrosis caused by late current season infection with leafroll and is tolerant to common scab.

Ute Russet: An oblong Russet potato cultivar with resistance to leafroll net necrosis andSclerotium rolfsii

Ute Russet is an oblong, smooth, fresh market potato with a dark net. It emerges slowly, produces an erect, medium sized vine, and is late maturing. Ute Russet is resistant toSclerotium rolfsii Sacc, and leafroll net necrosis, and moderately resistant toVerticillium wilt and scab. Its total and U.S. No. 1 yield potential is comparable to Centennial Russet in the San Luis Valley of Colorado and greater than Centennial Russet in Kern County, California.

Campbell 14: A verticillium resistant round white potato variety

The Campbell 14 potato variety is a medium-late maturing variety with round to oblong, smooth, shallow-eyed, white tubers. This variety is intended primarily for fresh market; however, under some conditions chip color will be acceptable. Campbell 14 is resistant to verticillium wilt and to the net necrosis caused by the potato leafroll virus.

Sunrise: An early maturing, golden nematode resistant, round, white potato variety

The Sunrise potato variety is an early maturing variety with round to oblong, moderately smooth, white skinned tubers with medium-shallow eyes. Its characteristics are closely parallel to those of Superior, except Sunrise is resistant to race A of the golden nematode (Globodera rostochiensis). Sunrise is primarily a table potato; however, in southern areas it can be used for chips when processed without prolonged storage at low temperatures. Sunrise is resistant to virus X and does not show the net necrosis symptoms caused by leafroll virus. Its parents are Wauseon and B 6563-2, a selection from the USDA breeding program.

Yankee Supreme: A new bruise-resistant potato variety

The Yankee Supreme potato is a medium to medium-late maturing variety with round to oblong, moderately smooth, shallow-eyed, buff-colored tubers. It is characterized by bruise resistance and high dry matter. Tubers can be used for fresh market or processing. Although chip color is often marginal, this variety can be reconditioned to its original color after cold storage. Yankee Supreme is resistant to virus X and to net necrosis caused by the leaf-roll virus.

Islander: A golden nematode resistant potato variety for fresh market and chipping

The Islander potato variety is a medium maturing variety with oblong, shallow-eyed, white-skinned tubers. High dry matter and good chip color characterize this variety which is better adapted to Long Island, New York and New Jersey than to other northeastern areas. It is resistant to golden nematode and net necrosis; moderately resistant to common scab and early blight; and less susceptible than most varieties to acid scab and Rhizoctonia. The Islander is a product of the cross Chipbelle × Norchip.

Yankee Chipper: A new golden nematode resistant potato variety with wide adaptation in the northeastern United States

The Yankee Chipper potato is a medium maturing variety with round to oblong, smooth, white-skinned tubers. Acceptable yields, good dry matter and light chip color characterize this widely adapted variety. It is resistant to golden nematode and virus X, and tubers do not show the net necrosis associated with leafroll virus infection.

Russette: A Russet-skin potato variety, combining high quality, high yields, and adaptation to the Northeastern states and Florida

Russette is a new, late maturing, russet potato variety adapted primarily for the northeastern United States and northern Florida. Tubers are oval to oblong, smooth with a medium-russet skin, and shallow eyes. Its specific gravity is similar to those of BelRus and Russet Burbank in areas of adaptation. Glycoalkaloid content is about 11 mg/100 g fresh weight. Baking quality is excellent, flesh is white, and best color of french fries is obtained from tubers stored at or above 13°C (55°F). Its long rest period makes it amenable to storage at a relatively high temperature before a chemical sprout inhibitor is needed. Russette is immune to virus A and leaf roll-induced tuber net necrosis; highly resistant to Verticillium wilt, tuber pinkeye, and tuber heat necrosis; and has good tolerance to scab, early blight, and Rhizoctonia infection of sprouts, stolon, and roots. Losses to rots and shrinkage in storage have been minimal. Russette is not resistant to viruses X, S, Y, and leaf roll and bacterial ring rot. Russette emerges to a stand about 10 days later than most varieties, however, subsequent vine growth is rapid until tuberization begins. Large-sized tubers may develop hollow heart under a late-season regime of high nitrogen and high moisture. A 22–30 cm (9″- to -12″) seed-piece spacing and 220 kg/ha (180 pounds/a) of nitrogen are recommended for production on mineral soils.

Use of IKI leafroll test to reduce net necrosis storage losses of potatoes

An iodine-potassium-iodide (IKI) starch staining procedure was adapted for use on potato plant leaflets to estimate the frequency of potato leafroll virus (PLRV) infection in potato fields prior to harvest. Large increases in the percentage of tubers with net necrosis occurred during storage among tubers from fields with high PLRV infection rates. Such fields were reliably identified prior to harvest by the IKI test, so their tubers could be processed at harvest to avoid net necrosis storage losses. The test could be performed on hundreds of samples per hour by untrained personnel with commonly available equipment. PLRV infection frequency varied widely in Columbia Basin potato fields. Most infected plants expressed no symptoms but could be detected by the IKI test before harvest. High rates of virus dissemination apparently occur late in the growing season in the Columbia Basin

Conestoga: A new early potato cultivar with very good table and chipping qualities

Conestoga is an early, white-skinned potato with very vigorous early growth. It has very good boiling, baking and chipping qualities. Yield is comparable to that of Superior, with chip colour and specific gravity slightly higher than Norchip’s. Conestoga is moderately resistant to virus leafroll, net necrosis, early blight, and common scab and moderately susceptible to mild and rugose mosaic.