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Sage Russet was released in 2009 by Oregon State University, in cooperation with the USDA-ARS and the Agricultural Experiment Stations of Idaho and Washington. It is a product of the Northwest Potato Variety (Tri-State) Development Program. Sage Russet has a medium-early maturity and produces long, somewhat flattened tubers with medium russeting of the skin. Total yields of Sage Russet are similar to those of Russet Burbank and Ranger Russet, but are significantly higher than those of Russet Norkotah. Sage Russet has significantly higher U.S. No.1 yields than Russet Burbank, Russet Norkotah, and Ranger Russet. It can be grown as an early or late crop with high U.S. No.1 yields and minimal internal defects. It achieved very high merit scores in processing and fresh market in Western Regional trials and can be considered for both markets. Sage Russet has a medium to high fertility requirements with high nitrogen use efficiency and medium storage capability. Sage Russet has moderate specific gravity and produces lighter fry color than the industry standard varieties. The color of fried strips following tuber storage at 4.4 °C and 7.2 °C is significantly lighter for Sage Russet than the control varieties, indicating good cold sweetening resistance. Chemical analyses have shown that Sage Russet has higher protein and vitamin C content than control varieties. Sage Russet is moderately resistant to early dying, early blight, and common scab, is resistant to tuber late blight, but susceptible to Fusarium wilt and is prone to shatter bruise.

Owyhee Russet (AO96160-3) originated from a cross between A89384-10 and A89512-3 in 1996. Owyhee Russet was released in 2009 by Oregon State University, in cooperation with the USDA-ARS and the Agricultural Experiment Stations of Idaho and Washington and is a product of the Northwest Potato Variety (Tri-State) Development Program. Owyhee Russet has semi-erect medium sized vines with medium to late maturity. The tubers are long, with a tan skin, medium russeting, and attractive tuber appearance for fresh market. Owyhee Russet was evaluated in several locations across the Northwest for more than 15 years. Total yield of Owyhee Russet is similar to that of Russet Burbank and Ranger Russet but significantly higher than Russet Norkotah. U.S. No.1 tuber yield of Owyhee Russet is significantly higher than Russet Burbank and Russet Norkotah, resulting in substantially higher marketable yield. Owyhee Russet tubers have significantly higher specific gravity than Russet Burbank and Russet Norkotah. Fry color following tuber storage at 4°C and 9°C is significantly lighter for Owyhee Russet than the comparison varieties. Relative strengths include high yield with a very high proportion of U.S. No.1 tubers, good tuber appearance and excellent processing quality, resistance to cold sweetening, common scab and Fusarium dry rot. Weaknesses include susceptibility to foliar and tuber late blight and susceptibility to metribuzin herbicide injury. Allelic patterns of five SSR markers have shown that Owyhee Russet has a distinctive DNA genetic fingerprint from its russet type reference varieties which are Ranger Russet, Russet Burbank, and Russet Norkotah.

Palisade Russet is a medium-late maturing, lightly russeted potato cultivar notable for its resistance to late blight (Phytophthora infestans) infection of foliage and tuber. Palisade Russet is suitable for processing with low tuber glucose concentrations observed following long-term storage at a temperature as low as 5.6°C with consistently acceptable fry color scores (USDA value ≤2.0) following storage at temperatures of 5.6 to 8.9°C. Reducing sugars are also maintained uniformly throughout the tuber, resulting in a low incidence of sugar ends in French fries relative to standard processing cultivars such as Russet Burbank and Ranger Russet. Palisade Russet has shown high specific gravities in western production regions of the U.S. which may limit its acceptance by the western processing industry. However, in potato production regions with inherently low specific gravities, Palisade Russet could have potential as a processing cultivar. In full-season trials conducted in Idaho, Oregon, and Washington over a 5 year period, the average total yield of Palisade Russet across all three states was very similar to yields observed for Ranger Russet and Russet Burbank. However, the U.S. No. 1 yield of Palisade Russet was 3% and 31% higher relative to Ranger Russet and Russet Burbank, respectively. In addition to late blight, Palisade Russet is also resistant to Verticillium wilt, black dot, and pink rot, and has a moderate level of resistance to net necrosis, PVY, and early blight of both the foliage and tuber. The disease resistances of Palisade Russet make it a good candidate for organic production, or for use by growers seeking reduced pesticide inputs. Palisade Russet displays a low incidence of second growth and growth cracks, especially relative to Russet Burbank, and is intermediate between Ranger Russet and Russet Burbank for incidence of hollow heart/brown center. Blackspot bruise expression for Palisade Russet is less pronounced than for either Ranger Russet or Russet Burbank, however it is slightly more susceptible to shatter bruise. Palisade Russet was released in 2011 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Pacific Northwest Potato Variety (Tri-State) Development Program.

Clearwater Russet is a medium-late maturing, russet-skinned, potato cultivar suitable for processing or fresh pack. It is notable for having a low incidence of external defects that contributes to its high U.S. No 1 yield relative to the dual-purpose industry standard, Russet Burbank. Clearwater Russet also maintains low glucose concentrations in its tubers during long-term storage making it an exceptional processing variety. With its low incidence of sugar ends and cold-induced sweetening resistance, Clearwater Russet can be stored at a temperature of 7.2°C for up to 250 days without the need for reconditioning; fry color from this storage regime is consistently ≤1.0 (USDA Fry Color Scale). This cultivar is also notable for its high tuber protein content, which was 33% greater than that of Russet Burbank. In full-season trials conducted over a 3-year period in California, Colorado, Idaho, Oregon, and Washington, Clearwater Russet had total yields slightly lower than Ranger Russet and Russet Burbank, but averaged 1% and 33% higher U.S. No. 1 yields, respectively, across all states. Average specific gravity of Clearwater Russet is comparable to Ranger Russet and significantly higher than Russet Burbank. Clearwater Russet is resistant to potato virus X (PVX) and tuber late blight and is moderately resistant to Verticillium wilt, common scab, and the common strain of potato virus Y (PVYO). Symptoms of infection with two necrotic strains of PVY were not observed in tubers of Clearwater Russet or Russet Burbank, but were observed in Ranger Russet. Blackspot bruise reaction for Clearwater Russet is less pronounced than for either Ranger Russet or Russet Burbank. The incidence of hollow heart in Clearwater Russet is intermediate between Ranger Russet and Russet Burbank. Internal brown spot has been noted as a problem for Clearwater Russet in the Columbia Basin of Oregon, but has not been observed as problematic in other growing regions. Clearwater Russet was released in 2008 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Pacific Northwest Potato Variety (Tri-State) Development Program.

Yukon Gem is a yellow-fleshed, medium to early-maturing cultivar suitable for fresh-pack or processing with a high level of resistance to potato virus Y O , and moderate foliar and tuber resistance to late blight. Multiple trials demonstrated a higher yield potential than Yukon Gold (yellow-fleshed industry standard). Yukon Gem produces uniform attractive tubers with light yellow skin and splashes of pink around the eyes; with flesh color similar to Yukon Gold. Yukon Gem was obtained from the intercrossing of Brodick and Yukon Gold at North Dakota State University (NDSU). An NDSU seedling tuber was sent and selected at Aberdeen, ID in 1995 and designated NDA5507-3YF. It advanced through the Aberdeen potato breeding program and regional trials in the western and northwestern U.S. Yukon Gem was released in 2006 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Northwest Potato Variety (Tri-State) Development Program.

Classic Russet is a medium maturing potato cultivar with rapid tuber bulking making it suitable for early harvest, as well as full-season production. Classic Russet is notable for its attractive tubers with medium russet skin and excellent culinary characteristics. It resulted from a 1995 cross between Blazer Russet and Summit Russet and was released in 2009 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon and Washington and is a product of the Northwest Potato Variety (Tri-State) Development Program. Classic Russet also shows potential as an early season processing cultivar, with fry color comparable to Russet Burbank and Ranger Russet. Classic Russet total yields were comparable to Russet Norkotah and Ranger Russet in early harvest trials and comparable to Ranger Russet and Russet Burbank in full season trials. When averaged across sites in early harvest or full season trials, U.S. No. 1 yields of Classic Russet were generally greater than those of Russet Norkotah, Ranger Russet, and Russet Burbank. Protein content for Classic Russet is relatively high, averaging 22% higher than Ranger Russet, 32% higher than Russet Burbank and 24% higher than Russet Norkotah. Specific gravity of Classic Russet in early harvest trials was comparable to Russet Norkotah but lower than Ranger Russet and was similar to Russet Burbank in full season trials. The incidence of hollow heart in Classic Russet is low, similar to that of Ranger Russet. It is less susceptible to blackspot bruise than Russet Burbank, Ranger Russet and Russet Norkotah but shatter bruise can be a concern if not matured properly prior to harvest. Classic Russet is moderately resistant to common scab and dry rot and is moderately susceptible to foliar and tuber infections of early blight and symptoms of corky ringspot. It is susceptible to Verticillium wilt, soft rot, foliar and tuber late blight, PLRV and PLRV net necrosis, and the common strain of potato virus Y (PVY°).

Common scab (CS), caused by Streptomyces spp., is a soil-borne bacterial disease of potato tubers which may cause superficial, raised, or pitted lesions. The results of screening potato germplasm for severity of CS can be variable, necessitating testing over multiple environments. The purposes of this study were to evaluate advanced germplasm from public potato breeding programs in different regions of the United States for their reaction to CS, estimate broad-sense heritability for resistance, and identify clones with stable resistance. Seventeen to 23 clones per year were evaluated at each of three locations (ID, ME, MN) from 2002 to 2007. After harvest, each tuber was scored for the percent of surface area covered with lesions and the type of lesion. These scores were converted to an area index (AI) and a lesion index (LI). AI, LI, and the arcsine √ proportion scabby tubers (PS) were analyzed as normally distributed responses. There were significant differences among clones for AI in 2 years, LI in 5 years, and PS in 3 years. There were significant clone x location interactions for AI and PS all 6 years, and LI in 5 years. Broad-sense heritability for AI, LI, and PS ranged from 0 to 0.78, 0.49 to 0.90, and 0.30 to 0.80, respectively. Evaluation at multiple sites remains important for characterizing the reaction of potato germplasm to CS.

We devised a method for screening various substances for possible aphid repellency. Corn leaf aphids (Rhopalosiphum maidis) were released in an arena and allowed to select paired green tiles coated with petroleum jelly alone or petroleum jelly containing 1% of the substance being tested. Aphids adhering to tiles were counted 24 h later. If significantly fewer aphids landed on treated tiles, the substance was considered to have potential for repelling aphids. Fifty-five substances were tested. Most showed no activity, but several including β-citronellol, farnesol, geraniol, linalool, oils distilled from several species of Artemisia and Achillea millefolia (yarrow) oil showed some promise.

Highland Russet is a late-season potato variety with light russet skin notable for its high yield of uniform U.S. No. 1 tubers, and good processing and culinary qualities. It resulted from a 1990 cross between Ranger Russet and Russet Legend and has been evaluated for over 15 years in public and industry trials throughout the western U.S. Highland Russet was released in 2006 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon and Washington and is a product of the Northwest Potato Variety (Tri-State) Development Program. It is suitable for processing into French fries and other frozen potato products and due to its large blocky shape, recovers a high proportion of fries per unit weight of tubers. Fry color and processing ratings for Highland Russet were similar to Ranger Russet and Russet Burbank but fry color uniformity was higher than either of the standard varieties. In full-season trials conducted over a three-year period in the states of Idaho, Oregon, Washington, Colorado, and California; Highland Russet averaged 7% and 9% higher total yields and 21% and 52% higher U.S. No. 1 yields than Ranger Russet and Russet Burbank, respectively. It has moderately high specific gravity, with values similar to Ranger Russet and higher than Russet Burbank. Highland Russet is moderately resistant to Verticillium wilt and powdery scab root galling, as well as to tuber infections of late blight. It is also moderately resistant to common strains of potato virus Y (PVYO) but is susceptible to PVYNTN. It is moderately susceptible to pink rot, common scab, powdery scab of the tuber and early blight of the tuber, as well as to Pectobacterium soft rot and Fusarium dry rot. Highland Russet is susceptible to foliar late blight, PLRV infection, Root-knot nematode and corky ringspot but is moderately resistant to PLRV net necrosis. The incidence of hollow heart in Highland Russet is low, similar to that of Ranger Russet and lower than Russet Burbank, Blackspot bruise reaction of Highland Russet is similar to Russet Burbank but it is less susceptible to shatter bruise.

Premier Russet is a russet-skinned, high yielding potato cultivar suitable for processing or fresh-pack. Premier Russet is notable for its resistance to the accumulation of reducing sugars in its tubers. This characteristic allows tubers of Premier Russet to be stored at temperatures as low as 5.6°C for 250 days without the need for reconditioning prior to processing. The low temperature sweetening resistance of Premier Russet allows for its storage at colder temperatures which contributes to prolonged tuber dormancy and quality, and to a reduction in the incidence and severity of storage diseases associated with the higher storage temperatures typically used for industry-standard cultivars such as Russet Burbank and Ranger Russet. Premier Russet was released in 2006 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Northwest Potato Variety (Tri-State) Development Program. In full-season trials conducted over a 3-year period in the states of Idaho, Oregon, Washington, Colorado, California, New Mexico, and Texas, Premier Russet averaged 5% and 4% higher yields than Ranger Russet and Russet Burbank, respectively, and had a higher percentage of US No. 1 yield than either cultivar. Specific gravity of Premier Russet is consistently greater than that of Ranger Russet or Russet Burbank. Premier Russet is resistant to common and powdery scab, very resistant to the common strain of potato virus Y (PVYO), and moderately resistant to Verticillium wilt, early blight of the foliage and tuber, Pectobacterium (Erwinia) soft rot, and to galling of roots by powdery scab. Blackspot bruise reaction for Premier Russet is similar to that of Ranger Russet. The incidence of hollow heart in Premier Russet is higher than that of Ranger Russet or Russet Burbank. Cultural recommendations to manage hollow heart in Premier Russet are provided.

‘Blazer Russet’ is an early to mid-season cultivar notable for its high U.S. No. 1 yield of medium-russeted tubers and its good processing and culinary qualities. It was derived from the cross A7816-14 x ‘NorKing Russet’ and was released in 2005 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon and Washington. Blazer Russet is very suitable for processing into French fries and other frozen potato products directly from the field or from extended storage, with higher merit scores than ‘Russet Burbank’ and ‘Ranger Russet’ in processing and post-harvest evaluations. Blazer Russet also has high merit for use in the fresh market, with sensory evaluations comparable to those of Russet Burbank. Total yields for Blazer Russet at five early harvest trial locations in the western United States were 12% greater than either ‘Russet Norkotah’ or ‘Shepody’, while U.S. No. 1 yields were 12% greater than Russet Norkotah and 35% greater than Shepody. Specific gravities of Blazer Russet tubers were comparable to tubers of Shepody, and higher than those of Russet Norkotah in early harvest trials. In full-season trials in the western United States, total yields for Blazer Rus set were slightly lower than Ranger Russet and slightly higher than Russet Burbank, but U.S. No. 1 yields were 8% greater than Ranger Russet and 38% greater than Russet Burbank. In these full-season trials, tuber specific gravity of Blazer Russet was similar to Russet Burbank, but lower than Ranger Russet. Blazer Russet is resistant to sugar ends, tuber malformations and most internal and external defects, the exception being its moderate susceptibility to hollow heart. Blazer Russet is resistant to common scab, tuber powdery scab and PVX, and has moderate resistance to blackspot bruise and tuber late blight infections. It is moderately susceptible to powdery scab root galling, PVY0, early blight infection of the tuber, Erwinia soft rot and Fusarium dry rot. Blazer Russet is susceptible to Verticillium wilt, pink rot, PLRV net necrosis, corky ringspot, and foliar early blight and late blight.

Toluca Valley, Mexico, is the putative center of origin and diversity forPhytophthora infestans (Mont.) de Bary, the oomycete pathogen responsible for late blight, making it an ideal location for screening potato breeding populations for late blight resistance. Approximately 21,500 progeny from the USDA-ARS, Aberdeen, Idaho potato breeding program were evaluated from 1996 through 2005 by estimating the percentage of defoliation due to late blight throughout the growing season. Comparisons of the number of resistant progeny and their degree of resistance response from resistant x susceptible (RxS) and resistant x resistant (RxR) crosses were made across years. A clone of each progeny planted in Toluca Valley was also planted the same year near Aberdeen, Idaho, to screen for acceptable tuber type. Promising progeny phenotypes were then screened the following year for tuber late blight resistance at field plots near Corvallis, Oregon. The RxR late blight crosses produced 64% resistant progeny compared to 29% of the RxS crosses. The segregation for late blight resistance in progeny from specific RxS crosses best fits a 1R:3S ratio. This segregation ratio is best explained by a gene model in which resistance is conferred by the presence of a dominant allele at each of two loci. The greater percentage of resistant progeny from RxR crosses indicates the benefits of pyramiding resistance genes from diverse germplasm. Three promising late blight resistant parental clones with acceptable tuber type resulted from family A95053. Family A95053 has multiple sources of resistance that includeSolarium demissum andSolarium stoloniferum, via female parent AWN86514-2 and male parent, B0718-3.

Western Russet, designated experimentally as A7961-1, and resulting from the cross A68113-4 x Bel-Rus, was released in 2004 by the USDA/ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. The foliage of Western Russet is spreading, with medium-sized olive-green leaves and abundant white flowers. The tubers are tan, with medium russet skin, oblong shape, a slightly prominent eyebrow, white flesh, and distinctly visible pith. Western Russet was compared with Russet Burbank in trials across the Pacific Northwest for yield, quality, and disease response. In general, Western Russet produced lower total yields than Russet Burbank, but on average and depending on location, similar U.S. No. 1 yields. When observed for defect problems, Western Russet exhibited resistance to second growth, growth cracks, shatter bruise, stem-end discoloration, and heat necrosis, moderate resistance to hollow heart, and moderate susceptibility to blackspot bruise. In product quality tests, Western Russet was rated similar to Russet Burbank for french fry and dehydrated potato flake quality and slightly inferior for baked potato quality. In replicated evaluations, Western Russet was found to have good field resistance to common scab and PVYo, and moderate resistance to verticillium wilt and tuber net necrosis caused by PLRV. It demonstrated susceptibility to late blight, foliar PLRV, dry rot, soft rot, and tuber early blight. Biochemical analysis of Western Russet tubers showed markedly higher vitamin C content than those of Russet Burbank. Tuber glycoalkaloid concentration in tubers produced in a 1988 trial was 1.0 mg 100 g−1.

GemStar Russet, derived from the cross Gem Russet x A8341-5, was released in 2004 by the USDA/ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. The foliage of GemStar Russet is dark yellowish-green, spreading, with large leaves and abundant white flowers. The tubers are brown, medium to heavily russeted, oblong, with a slightly prominent eyebrow, white flesh, and indistinct pith. GemStar Russet was compared with Russet Burbank and Russet Norkotah in trials across the Pacific Northwest for yield, quality, and disease response. Except for locations in southern Idaho, in general, GemStar Russet produced slightly lower total yield than Russet Burbank, but much higher U.S. No. 1 yield. When compared with Russet Norkotah, GemStar Russet produced similar total and U.S. No. 1 yields in early harvest trials but higher total and U.S. No. 1 yields in late-harvest trials. When observed for defect problems, GemStar Russet exhibited resistance to second growth, growth cracks, and stemend discoloration, moderate resistance to blackspot and shatter bruising, but a high level of susceptibility to hollow heart. In product quality tests, GemStar Russet was rated superior to Russet Burbank for french fry quality and comparable for baked potato quality. GemStar Russet was found to be immune to PVX, resistant to common scab and powdery scab, moderately resistant to Verticillium wilt, tuber net necrosis caused by PLRV, and corky ringspot. It demonstrated susceptibility to late blight, PLRV, dry rot, soft rot, and ringrot and extreme susceptibility to PVYo. Biochemical analysis of GemStar Russet tubers showed them to be higher in protein and much higher in vitamin C than those of Russet Burbank or Russet Norkotah. Three-year average for tuber glycoalkaloid concentration was 1.5 mg 100 g−1.

The potato cultivar Defender is high-yielding, white-skinned, and notable for having foliar and tuber resistance to late blight infection caused byPhytophthora infestans (Mont.) de Bary. It was released in 2004 by the USDA-ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. Defender is suitable for processing into french fries and other frozen potato products directly from the field or from storage. Defender also may be used for fresh markets in regions such as California, where cultivars with long tubers and white skin are traditionally grown. Resistances to late blight and other potato diseases make Defender an ideal candidate for organic potato production. Defender consistently produced greater total and U.S. No. 1 yields than ‘Russet Burbank’ in Idaho trials. In early harvest trials conducted in the western U.S., average total yields of Defender were 17% and 23% greater than yields for ‘Ranger Russet’ and ‘Shepody’, respectively. In full-season trials conducted in the western U.S., Defender averaged 10% and 15% higher yields than Ranger Russet and Russet Burbank, respectively. Specific gravity of Defender is consistently high, with values comparable to those of Ranger Russet; tuber ascorbic acid (Vitamin C) levels are also high. In addition to late blight, Defender also is resistant to tuber early blight (Alternaria solani, (Ellis & G. Martin), L.R. Jones & Grout), potato virus X, and net necrosis; it has moderate levels of resistance to Verticillium wilt (Verticillium dahliae, Kleb), pink rot, foliar early blight, corky ringspot, and Erwinia soft rot. Defender is susceptible to scab (common and powdery) and potato leafroll virus; it has moderate susceptibility to dry rot (Fusarium spp.) and potato virus Y. Susceptibilities to internal necrosis, tuber greening, and blackspot bruise also have been noted, but may be minimized through cultural and harvest practices.

Steroidal glycoalkaloids (SGAs) are secondary metabolites of Solanaceous plants. Two predominant glycoalkaloids, a-chaconine and asolanine are produced in potatoes. An antisense transgene was constructed to down-regulate glycoalkaloid biosynthesis using a potato cDNA encoding a sterol alkaloid glycosyltransferase (Sgt1). Introduction of this construct into potatoes resulted in some lines with an almost complete inhibition of a-solanine accumulation. This inhibition was compensated by elevated levels of a-chaconine and resulted in wild type total SGA levels in the transgenic lines. In vitro assays with the recombinant SGT1 isolated from yeast demonstrated that Sgt1 encodes an enzyme capable of both glucosyltransferase and galactosyltransferase activity with a preference for UDP-galactose as the sugar donor. Together this data confirms SGT1’s role in vivo as the solanidine:UDP-galactose galactosyltransferase. # 2004 Elsevier Ireland Ltd. All rights reserved.

‘Alturas’, a late-maturing, high-yielding, russet potato cultivar with high tuber specific gravity, was released in 2002 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington. Originally selected for dehydration processing, its cold-sweetening resistance also makes it suitable for processing out of storage into french fries and other frozen potato products. Culinary quality is high, with larger tubers suitable for fresh market if heavily russeted skin is not essential. Alturas consistently produced greater total and U.S. No. 1 yields than ‘Russet Burbank’ and ‘Ranger Russet’ in southern Idaho trials. Across other western trial sites, total yields of Alturas have on average been 29% and 14% greater than Russet Burbank and Ranger Russet, respectively. Alturas is resistant to Verticillium wilt (Verticillium dahliae) and early blight (Alternaria solani). Compared with Russet Burbank and Ranger Russet, Alturas is less susceptible to corky ringspot and foliar and tuber infection by late blight (Phytophthora infestans). It also is less susceptible to tuber net necrosis and Fusarium dry rot than Russet Burbank, and is more resistant to common scab (Streptomyces scabies) than Ranger Russet. However, Alturas is more susceptible to infection by PVY and PVX than Ranger Russet. Total nitrogen application recommendations for Alturas are approximately 40% less than those for Russet Burbank. Alturas requires 15% to 20% more water during the growing season than does Russet Bur-bank.

The Agricultural Experiment Stations of Oregon, Idaho, and Washington and the U.S. Department of Agriculture jointly released Wallowa Russet in 2002. This late maturing variety is most suitable for frozen french fry use, but may find limited fresh market potential because of outstanding flavor and texture when baked. Wallowa Russet was evaluated as AO87277-6 in Oregon irrigated trials from 1993 through 1999, and in western regional trials from 1997 through 1999. Averaged over 13 locations in seven states, Wallowa Russet produced total yields of 55.6 mt/ha compared to 53.5 and 45.7 mt/ha for Russet Burbank and Russet Norkotah, respectively, and U.S. No.1 yields of 44.4 mt/ha compared to 30.7 and 36.0 mt/ha for Russet Burbank and Russet Norkotah. Specific gravity is consistently higher for Walowa Russet than for Russet Burbank and fry color is as light or lighter; sugar end development is less than that observed in Russet Burbank. Wallowa Russet is similar to Russet Burbank in susceptibility toVerticillium wilt, foliar early blight (Alternaria solani), and potato leafroll virus (PLRV). However, Wallowa Russet develops less net necrosis than Russet Burbank from PLRV infection. Wallowa Russet is more susceptible to common scab (Streptomyces scabies) than Russet Burbank. It has moderate resistance to potato virus Y (PVY). Tubers of Wallowa Russet are less susceptible to tuber infection and decay caused by potato late blight (Phytophthora infestans) than Russet Norkotah and Ranger Russet. Wallowa Russet has less hollow heart, brown center, blackspot bruise, and fewer growth cracks than Russet Burbank but is more susceptible to shatter bruise. Vitamin C is higher for Wallowa Russet (30.4 mg/100 g fresh weight) than for Russet Burbank (21.9) or Russet Norkotah (22.0), and protein content averaged 5.6% compared to 4.7% and 4.9% for Russet Burbank and Russet Norkotah, respectively.

Ivory Crisp was released in 2002 by the experiment stations of Idaho, Oregon, Washington, and North Dakota, and by the USDA/ARS. It resulted from a 1980 cross of ND292-1 and A77268-4. Ivory Crisp is suited for use in both the direct delivery and storage chipping markets. Ivory Crisp is a medium-maturing potato variety with round, white tubers and excellent chipping quality. It has medium to high yield potential, high tuber solids, resistance to most internal and external tuber defects, and the ability to chip from cold storage. In trials in Idaho, Oregon, and Washington, total and U.S. No. 1 tuber yield of Ivory Crisp was similar to Atlantic but lower than Chipeta. Yield of tubers in the size range 113–336 g for Ivory Crisp is higher than for either Atlantic or Chipeta. Ivory Crisp is resistant to growth cracks, secondary growth, hollow heart, and stem-end necrosis, but susceptible to shatter bruise. Tuber sugar content has consistently remained low following cold storage and near-acceptable chip color retained at 4.4 C. Ivory Crisp is susceptible or moderately susceptible to most common field diseases of potato. It is highly susceptible to common scab, powdery scab, and pink rot. Tubers of Ivory Crisp have dry matter content (22.4%) lower than those of Atlantic, but higher than those of Chipeta. Glycoalkaloid content of Ivory Crisp tubers is very low (4.3 mg 100 g-1). An application for Plant Variety Protection has been filed for Ivory Crisp. Seed is available from potato seed growers in Idaho, North Dakota, and Canada. Small amounts of seed, for research purposes, can be obtained by contacting the corresponding author.

Green tile pan trap counts during the potato-growing season showed thatCapitophorus elaeagni (32%),Diuraphis noxia (27.7%), andMetopolophium dirhodum (15%) were the most abundant aphid species in potato fields at Aberdeen, Idaho.Acyrthosiphon pisum (22%),C. elaeagni (19%), andMetopolophium dirhodum (19%) were the most abundant species in potato fields at Tetonia, Idaho potato seed production areas. Eight species of aphids found to visit potato fields (C. elaeagni, D. noxia, M. dirhodum, Myzus persicae, Rhopalosiphum maidis, Rhopalosiphum padi, Schizaphis graminum, andSitobion avenue) were tested for Potato virus Y (PVY) transmission efficiency by timed probe experiments. Four of these species (D. noxia, M. dirhodum, M. persicae, andS. aoenae) and an additional three (Diuraphis frequens, Diuraphis mexicana, andDiuraphis tritici) were tested using mass inoculations.Capitophorus elaeagni, M. persicae, R. maidis, R. padi, andS. graminum all transmitted PVY in the timed probe experiments.Myzus persicae andD. noxia transmitted PVY in the mass inoculation experiments.

IdaRose is a late-maturing, potato variety with round, dark red tubers. It has high yield potential and exceptionally long tuber dormancy. IdaRose was released in 2000 by the USDA/ARS and the experiment stations of Idaho, Oregon, and Washington. It resulted from a 1982 cross of Sangre and TXA218-7. IdaRose is suited for use in both the early summer and storage fresh markets. Tuber yield of IdaRose is higher than that of Dark Red Norland and Sangre. It has yield potential similar to or slightly lower than Red LaSoda. Tubers of IdaRose have good internal and external quality. Culinary quality of boiled, baked, and micro-waved IdaRose tubers is excellent. It has moderate resistance to growth cracks, hollow heart, and other defect problems. IdaRose is susceptible or moderately susceptible to most common field diseases of potato. Tubers of IdaRose have dry matter content (19.2%) similar to other standard red varieties, and have a relatively high concentration of sugars and low concentration of glycoalkaloids (2.4 mg/100 g).

Gem Russet, a new medium maturing, long russet potato variety, was released in 2000 by the USDA/ARS and the experiment stations of Idaho, Oregon, and Washington. It is suited for use in the fresh, frozen-fried processing, and dehydration markets. Total tuber yield of Gem Russet is similar to that of Russet Burbank when grown in eastern Idaho, but lower when grown in the long-season areas of western Idaho and the Columbia Basin of Oregon and Washington. U.S. No. 1 yield is consistently higher that that of Russet Burbank. Tubers of Gem Russet have good processing and baked quality. Gem Russet is resistant to most external and internal physiological defects, including second growth, growth cracks, shatter bruise, and hollow heart. It is moderately susceptible to blackspot bruise. Gem Russet shows extreme resistance to potato virus X, resistance to common scab, and moderate resistance to early dying. Biochemical analysis of Gem Russet tubers has shown higher solids, lower reducing sugar and glycoalkaloid content, and higher concentration of protein and vitamin C when compared with tubers of Russet Burbank.

Potato varieties of Europe, widely grown prior to the late blight epidemic of the 1840s, were apparently derived mainly from ChileanSolanum tuberosum Group (Gp) Tuberosum and with contributions from Gp Andigena. A small number of these old varieties had field resistance and consequently survived the late blight. These survivors, along with a limited number of 19th and early 20th century introductions, provided the very narrow genetic base for our modern potato variety development. Beginning in the first half of the 20th century, resistance to diseases and pests from exotic species and primitive relatives was backcrossed into the existing parental stocks, with little improvement in broadening of the genebase. By the 1980s, 77% of European and somewhat fewer North American varieties had genes, derived by backcrossing, fromS. demissum (late blight resistance) and Andigena (resistance to cyst nematode). Broadening of the Tuberosum genebase was undertaken in 1959 by creating long-day adapted Neo-Tuberosum (N-T) from large populations of Andigena. This took six or more cycles of recurrent mass selection. Simmonds, in England, was the first to begin this work, followed shortly after by Plaisted, in the U.S., and Tarn, in Canada. Varieties with N-T in their pedigrees include the New York releases “Rosa”, which is 50% N-T, and “Eva”, 25% N-T. The Tuberosum genebase has also been broadened with diploid Gp Phureja resulting in the releases of “Yukon Gold,”with yellow flesh and high internal quality, and “NorValley,”a chipper with resistance to cold sweetening. Over 5000 accessions of about 150 wild species are available to breeders from the U.S. Department of Agriculture, National Research Support Project 6 (NRSP-6) genebank. Many of these accessions have been evaluated for resistance to diseases and pests as well as other important traits. Six genebanks in other countries also have many accessions for breeders. These seven collections are a great source of valuable traits for breeding, but remain under-utilized, mainly because of the time and additional resources required in eliminating the “wildness”characters associated with the desired traits. “Pre-breeding”is needed to help breeders utilize the many needed genes and alleles in the wild species. There now are two projects with pre-breeding as an objective in the U.S., one at Madison, WI, and the other at Prosser, WA. Resistance to cold sweetening (low sugar build up in cold storage) has been backcrossed from several wild species into the Tuberosum background, as has resistance to late blight, the Columbia rootknot nematode, and the potato leafroll virus (PLRV). Resistance to potato virus Y (PVY) and PLRV obtained from N-T has been incorporated into Tuberosum parental stocks. Durable resistance to late blight in Polish breeding stocks, withS. demissum andS. stoloniferum background, and in improved Bolivian and Peruvian Andigena has also been utilized by North American programs.

Klamath Russet, a late-maturing cultivar for fresh market use, was jointly released by the Agricultural Experiment Stations of Oregon, Idaho, and Washington and the U.S. Department of Agriculture in 2000. Klamath Russet was tested in irrigated trials in Oregon from 1990 to 1999 and in Western Regional Trials from 1994 to 1996. Klamath Russet yields of U.S. #ls have exceeded those for Russet Burbank and Russet Norkotah by more than 30%, averaged across all trials. Klamath Russet is moderately resistant to Verticillium wilt and highly resistant to common scab. Specific gravity for Klamath Russet has averaged 1.076 across all trials compared with 1.070 and 1.081 for Russet Norkotah and Russet Burbank, respectively. Klamath Russet is not considered suitable for french fry production because of high sugar and low starch contents.

Glucosylation of thaxtomin A by Streptomyces scabies occurs in vitro. The glucose conjugate of thaxtomin A (TA) from bacterial extracts was isolated and characterized as thaxtomin A-β-di- O -glucoside (TAG). On a specific activity basis, TAG was six times less toxic than TA in potato tuber slice tests. Evidence for glucosylation of TA in S. scabies includes electrospray mass spectroscopy, NMR spectroscopy, chromatographic data, and the unequivocal demonstration of the presence of glucose in the putative TAG after acid hydrolysis and GC-MS analysis. 14 C-thaxtomin A was produced by amending 6 day old cultures of S. scabies in oat meal broth with l -phenylalanine-UL- 14 C. The scab-resistant cultivar Nooksack and resistant selections of Ranger self-cross treated with 14 C-TA produced a higher amount of a radioactive metabolite with an R f value similar to TAG than the susceptible cultivar Ranger. Furthermore, there was almost twice as much glucose transferase on a specific activity basis in resistant than in susceptible potato cultivars and selections. Glucosylation appears to be a mechanism of TA detoxification in potato and is related to scab resistance and susceptibility in potato.

Century Russet, a high-yielding, late-maturing variety suitable for fresh tablestock use, was jointly released in 1995 by Agricultural Experiment Stations in Oregon, Idaho, Washington, Colorado, California, and Texas and the USDA Agricultural Research Service. Extremely high yields have been observed for Century Russet in variety trials conducted in Oregon and throughout the western United States under a wide range of soil and climatic conditions. Century Russet produced 40 percent higher marketable yields than Russet Burbank and 67 percent higher marketable yields than Russet Norkotah in 11 regional trials conducted over a three-year period in sevenwestern states. Uniform tuber shape, high yields of count carton sizes, and attractive tuber appearance make Century Russet well suited for the fresh market industry. It is not recommended for chipping or processing into frozen products because of low solids and dark fry color. Century Russet is highly resistant toVerticillium wilt and consistently develops less hollow heart, brown center, and other internal defects than Russet Burbank. It requires more time between vine kill and harvest than Russet Burbank for adequate tuber maturity and skin set. Bruised Century Russet tubers are susceptible to early blight andFusarium infection.

Umatilla Russet, a moderately late maturing variety especially suitable for frozen French fry processing but also acceptable for tablestock use (boiling, and baking), was jointly released by the Agricultural Experiment Stations of Oregon, Idaho, and Washington and the U.S. Department of Agriculture in 1998. Umatilla Russet was evaluated in irrigated trials in Oregon from 1988 to 1997, and in western regional trials from 1989 to 1991. Total yields were similar to those of Russet Burbank, but Umatilla Russet produced higher marketable yields. In three years of regional trials at up to 13 locations in seven western states, Umatilla Russet averaged 40.5 Mg/ha compared with 32.4 Mg/ha for Russet. Burbank. Umatilla Russet fry color and specific gravity are consistently equal to or better than for Russet Burbank. Umatilla Russet is less susceptible toVerticillium wilt than Russet Norkotah, less susceptible to net necrosis than Russet Burbank, and resistant to PVX. It is susceptible to PLRV and expresses foliar symptoms of PVY more clearly than Russet Norkotah. Umatilla Russet is less susceptible to tuber infection and decay caused byPhytophthora infestans than Ranger Russet and Russet Norkotah. Umatilla Russet is less susceptible to hollow heart, brown center, growth cracks, and sugar ends, but more susceptible to blackspot and shatter bruise than Russet Burbank

Potato germplasm was assessed for resistance to corky ringspot disease (CRS) incited by transmission of tobacco rattle virus (TRV). TRV is transmitted by the stubby root nematode,Paratrichodorus allius, in the Pacific Northwest, and characterized by necrotic areas in the tuber. Four tests were conducted at two different problem fields in Umatilla, OR and Pasco, WA. The fields differed in the virulence of the virus isolates. Some clones and named varieties showed resistance only in the field with the relatively mild Umatilla isolate, while others remained symptomless at both sites. The host suitability of test potatoes to threeP. allius populations from the region was determined in greenhouse pot tests, and expressed as reproductive values [Rf = (final population of nematode at 55 days) / (initial population)]. TheR f values for the nematodes were not correlated with resistance ratings based on visual scoring of CRS symptoms in field grown potatoes. Thus, it appears that CRS resistance is based on reaction of potato genotypes to virus and not the vector. The availability of resistant clones inin vitro form is indicated.

Blackspot bruise is a major problem in the fresh market and frozen french fry industry. The blackspot bruise potential of Russet Burbank and Ranger Russet in Idaho potato fields was determined by surveying commercial fields during 1993 and 1994. Management factors were monitored to determine what practices were contributing to blackspot susceptibility in addition to mechanical damage. The survey included 17 Russet Burbank and 3 Ranger Russet fields in 1993, and 28 Russet Burbank and 8 Ranger Russet fields in 1994. The 1993 season was unusually cool and wet whereas 1994 was warmer than normal, resulting in a wide range of environmental conditions for the 2 year study. Blackspot bruise potential was determined at different stages of tuber physioIogical maturity by collecting samples several weeks prior to normal harvest, immediately before harvest, and after storing sub-sampies for several months. The blackspot bruise potential was measured by both impact and abrasive peel tests. Field maturity was the factor most consistently related to blackspot potential both years. In 1994 a multiple regression of 3 independent variables - field maturity index, specific gravity, and percent available soil water at tuber sampling, compared with the blackspot potential as the dependent variable gave a correlation coefficient of r = 0.73 (p = 0.001). Due to the cool, wet growing season in 1993, there was not enough variability in specific gravity and available soft water among the fields sampled for these factors to correlate with the blackspot potential. The available

Potato breeding selection AWN86514-2, Solanum tuberosum gp tuberosum, is being released as germplasm that is highly resistant to prevalent North American strains of Phytophthora infestans. This selection has been tested under field conditions in Mount Vernon, Washington (P. infestans US11 and US8 with complex virulence pathotypes), as well as Corvallis, Oregon, and eight other locations in North America (predominantly P. infestans US8) between 1994 and 1997. Both foliage and tubers show partial resistance. Although AWN86514-2 is pollen sterile, it can be successfully used as a female parent. An average of 34% of the progeny from crosses between AWN86514-2 and four susceptible clones were resistant to late blight when tested at Toluca, Mexico, in 1996. AWN86514-2 also has high resistance to Verticillium wilt and potato virus Y. AWN86514-2 is late maturing, with medium yields of smooth, longoblong, buffskinned tubers. Specific gravity is high and french fry color from 7 C (45 F) storage is excellent. The male parent of AWN86514-2 was Ranger Russet, a dual purpose french fry and fresh market variety, and the female parent was KSA195-96, a selection made at Aberdeen, Idaho, from Polish germplasm received as true seed from the Polish Plant Breeding and Acclimatization Institute. Possible sources of the late blight resistance in this clone include S. acaule, S. demissum, S. phureja, S. simiplicifolium, S. stoloniferum, and S. tuberosum gp andigena which are in the lineage of KSA195-96. This germplasm was developed and released by USDA-ARS in cooperation with the Agricultural Experiment Stations of Idaho, Oregon, and Washington.

In 1994, potato samples for certification from Idaho seed fields reacted in enzyme-linked immunosorbent assay (ELISA) tests to a polyclonal potato carlavirus M (PVM) antiserum. Sample affinity to the antiserum was lower than control samples. Furthermore, ELISA-positive samples were obtained from both symptomatic as well as asymptomatic plants. A complementary DNA library was prepared using both reverse transcription-polymerase chain reaction and primers based on published PVM sequences, or oligo d(T) primed reverse transcribed sequences. The nucleotide sequence was determined for the 3′-terminus of the genome. Putative coat protein amino acid sequence was compared to published PVM and potato virus S coat protein sequences. While this new isolate is likely a strain of PVM, it is significantly different from known PVM coat protein sequences in the amino terminus region. These differences may explain the poor reactivity to other PVM antisera and suggest that it is a new strain of PVM, which we have designated PVM-ID.

Potato progenies in a line × tester mating design and the clonal parents were screened for field resistance to potato leafroll virus (PLRV) to determine the heritability of this trait. Twelve advanced potato clones or varieties were crossed as pistillate parents to two pollen testers. The seedling progenies and clonal parents were exposed to aphid-transmitted potato leafroll virus for two growing seasons. Cumulative infection by potato leafroll virus was determined by post-season serological indexing of foliage grown from sprouted tubers after 2 years of exposure. Narrow-sense heritability was estimated from regression of mid-parent on progeny as h 2 = 0.72. This estimate indicates a high level of useable genetic variance for PLRV resistance in advanced breeding materials. Although variation in resistance to PLRV appears to be a quantitative trait in susceptible and moderately resistant clones, performance of the most resistant parents suggests that genes with major effects may be present. These results are similar to the conclusions of other researchers who found one or two genes controlling the phenotypes of extreme resistance, resistance to infection, or suppression of virus titre.

A three-year study was conducted from 1991 through 1993 to evaluate the field performance of potato clones that had been selected for resistance to wilt symptom development and stem colonization byVerticillium dahliae. The total yield, size distribution, and specific-gravity of these highly resistant clones were compared with standard cultivars and two parent clones with high Verticillium resistance and high yield, A66107-51 and A68113-4. Two groups of Verticillium resistant germplasm were selected in 1991. One group was the highly resistant progeny from a cross between A66107-51 and A68113-4. The second group consisted of hybrids between wild species accessions with high Verticillium resistance and cultivated diploid and tetraploid germplasm.

Rishitin, lubimin, and solavetivone were the major sesquiterpenes found in 46 cultivars and breeding selections of potato (Solanum tuberosum L.). Concentrations of total sesquiterpenes were low or undetectable in untreated tuber slices, but ranged from 5 to 101 μg/g of fresh weight 4 days after treatment with the elicitor arachidonic acid. Seven genotypes produced significantly (P < 0.01) higher sesquiterpene concentrations than Russet Burbank (17 μg/g), a widely grown commercial cultivar. More than half of the genotypes tested were significantly (P < 0.01) different from Russet Burbank in sesquiterpene composition due to higher ratios of lubimin or solavetivone, both of which are reported to be biosynthetic precursors of rishitin. The highest ratios of solavetivone to total sesquiterpenes were strongly correlated with derivation from S. tuberosum ssp. andigena CPC 1673, which confers the H1 gene for resistance to the golden nematode (Globodera rostochiensis).

Potato germplasm with high levels of combined resistance to potato viruses X, Y, and leafroll was identified and used to produce improved parental clones with similarly high levels of resistance. Resistance was determined from the amount of tuber infection following inoculation of plants in the field. Parental germplasm with the best multiple resistance came from two backgrounds, eitherSolanum tuberosum group Andigena derived from the Cornell University neo-tuberosum program, or from complex hybrids ofS. tuberosum and wild solanums that were produced by the Max Planck Institute and the Polish Institute for Potato Research. Two Aberdeen, ID selections, A85519-6 and A85530-10, with gp. Andigena ancestry, have had no tuber-borne infection of PVX, PVY, or PLRV during four years of intensive field testing. We have not been successful in combining virus S resistance with resistance to the other viruses.

Transformed Russet Burbank and Lemhi Russet clones which contained three different transgene constructs were evaluated for performance under field conditions in Idaho. The transgenic lines were characterized over two growing seasons, using plants grown from both greenhouse produced minitubers (first year) and field grown seed (second year). Individual clones were evaluated for a variety of agronomic and quality properties. Many of the transformed clones showed reduced yield and increases in percent malformed and undersized tubers. Other characteristics, such as specific gravity and fry color, showed less variability. The variation observed in non-transgenic clones regenerated from tissue culture was less than that of the transformed lines. Out of an original population of 57 transgenic lines in tissue culture, maintenance of key agronomic and quality properties of the parental material was observed in only four clones. These results suggest that experiments designed to generate transgenic lines for the marketplace should be initiated with a large number of transgenic clones.

Blackspot pigment development was measured by three methods: 1) impact, 2) abrasive peeling, and 3) oxidation of tuber homogenates. Genotypes and storage periods were used as variable treatments. All methods were able to separate genotypes based on blackspot resistance although the abrasive peel and homogenization methods provided more consistent results than the impact bruise method. Bruise resistant genotypes transferred their resistance to progeny in crosses with a susceptible genotype which was correlated with tyrosine content. According to the traditional impact bruise technique, tuber resistance to blackspot increased during the eight-to ninemonth storage at 3 C. In contrast, resistance was found to decrease with the homogenization procedure and did not change with the abrasive peel technique. Free tyrosine was consistently associated with blackspot pigment development but chlorogenic acid and caffeic acid were not.

Inheritance of blackspot bruise reaction in tetraploid potato was studied using a five-parent half-diallel, including parental selfs. The parents were chosen to represent the full range of blackspot reactions. Four 12-plant replications of each family were grown at Aberdeen, Idaho and at Prosser, Washington. The abrasive-peel method was used to evaluate the blackspot reaction. Highly significant general combining ability (GCA) effects and specific combining ability (SCA) effects were observed for this trait. The GCA and SCA variances represented 59% and 9%, respectively, of the total variance. GCA effects are presented for the parents. The narrow sense heritability was 0.85. These results indicate that breeding for resistance to blackspot should be successful if resistant parents are used; backcrossing may be needed.

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.

Ten ‘Russet Burbank’ potato clones collected from various geographical regions of the United States and Canada were evaluated for plant and agronomic characteristics for two years at Aberdeen, Idaho. Clonal differences were detected for emergence time, stem number per hill, expression of Verticillium symptoms, some measures of yield, and percentage of tubers with hollow heart. Eight of the ten clones were quite similar. Differences were slight or found only in a few characteristics. One clone, collected from northern Idaho, was similar to the homogenous eight clones in all respects except yield, which was probably due to chronic PVX infection throughout the trial period. Another clone, collected from New Brunswick, was distinct from all other clones and was markedly inferior with respect to many of the characteristics measured when grown in Idaho.

Frontier Russet, a new, medium-early 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 April 9, 1990. It was tested in irrigated yield trials since 1979. Frontier Russet produces a moderately high yield of high quality, oblong to long, cylindrical, russet-skinned tubers. The tubers are well suited for baking and for processing into french fries at harvest. Frontier Russet is resistant to Fusarium dry rot and more resistant to Verticillium wilt than other early russets.

Gemchip, a new potato chipping variety, was released jointly by the U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Oregon, Washington, and Colorado on August 9, 1989. Gemchip was tested in irrigated yield and chipping trials in the Western U.S. since 1982. It outyielded Norchip by an average of 23% and Atlantic by 14%, and it chipped well both out of the field and out of storage. Gemchip is moderately late in maturity and resistant to Verticillium wilt.

The reaction of 40 potato clones and six accessions ofSolanum spp. to wilt caused byVerticillium dahliae and to the acetone precipitate (AP) of the toxin produced by the pathogen in vitro was studied. There was a highly significant correlation between the wilt reaction of the clones in the glasshouse, the incidence and progress of wilt and severe wilt in the field, and the degree of colonization of stem apices byV. dahliae. Of the clones and accessions evaluated, NDA8694-3, Norgold Russet, BelRus, Superior, Russet Norkotah, Norland andS. demissum were the most susceptible, while A66107-51, A68113-4, Targhee, NDA843-3, Alpha, A7805-8, A7816-14, Russet Nugget,S. chacoense, S. sparsipilum, andS. tarijense were the most resistant to wilt. The reaction of genotypes to the AP ofV. dahliae toxin in an excised leaf bioassay was not correlated with their reaction to Verticillium wilt in the field or glasshouse.

Potato breeding selections A66107-51 and A68113-4 (Solanum tuberosum gptuberosum) are being released as germplasm that is highly resistant to Verticillium wilt (Verticillium dahliae Kleb.) These selections have been extensively evaluated for resistance to Verticillium as measured by symptom severity and degree of colonization byV. dahliae. They combine outstanding wilt resistance with good tuber maturity characteristics, high yield, and french fry processing tuber type. A66107-51 has long-oblong, russeted tubers, with high yield and variable processing quality. A68113-4 has long-oblong, partially russeted tubers with high yield and good processing quality. Both selections are fertile as female parents, and A66107-51 is occasionally pollen fertile. The Verticillium resistance of these two clones has been transmitted to progeny. These selections were developed by USDA-ARS in cooperation with the Idaho Agricultural Experiment Station. Seed is available from USDA-ARS, Aberdeen, Idaho.

Polyphenol oxidase (PPO) activity of Russet Burbank potato was inhibited by sense and antisense PPO RNAs expressed from a tomato PPO cDNA under the control of the 35S promoter from the cauliflower mosaic virus. Transgenic Russet Burbank potato plants from 37 different lines were grown in the field. PPO activity and the level of enzymatic browning were measured in the tubers harvested from the field. Of the tubers from 28 transgenic lines that were sampled, tubers from 5 lines exhibited reduced browning. The level of PPO activity correlated with the reduction in enzymatic browning in these lines. These results indicate that expression of tomato PPO RNA in sense or antisense orientation inhibits PPO activity and enzymatic browning in the major commercial potato cultivar. Expression of tomato PPO RNA in sense orientation led to the greatest decrease in PPO activity and enzymatic browning, possibly due to cosuppression. These results suggest that expression of closely related heterologous genes can be used to prevent enzymatic browning in a wide variety of food crops without the application of various food additives.

The white potato became established in Europe and North America as an important crop during a 200 year period beginning in the mid 16th Century. The potato was first introduced to Europe from South America, either from the northern Andes as Solanum tuberosum gp. andigena (short day adapted), or from southern Chile as Solanum tuberosum gp. tuberosum (long day adapted) and the earliest descriptions are of what appear to be mixed genotypes (Salaman, 1949). From about 1550 to 1750, the potato was selected and adapted to the long day conditions of summer in the higher latitudes of Europe. By the late 1700s, distinct cultivars were recognized, and attempts were being made to improve the crop through cultivar selection. Problems with Potato leafroll virus genus Polerovirus, (PLRV) and Potato virus Y genus Potyvirus, (PVY) infection called “curl” induced the early breeders to select new clones with less symptoms and higher yields. Even though they did not really understand the cause of curl, they were quite adept at applied breeding, growing small populations from botanical seed, and then selecting the best seedlings. Cultivars, like White Kidney, Manly, and Lumper, to name a few from Great Britain and Ireland, came to be grown on a large scale, and there was less cultivar diversity than is present in more recent years in Europe (Salaman, 1949).

More than 50 isolates of Potato virus Y (PVY) with characteristics of strains that cause tobacco veinal necrosis (PVYN) were obtained from potatoes (Solanum tuberosum L.) grown in the northwestern United States. These isolates are being characterized at the biological and molecular levels. Isolate RR1 was obtained from leaves of potato cv. Ranger Russet showing distinct mottling and leaf deformity, which is in contrast to the leaf-drop and necrosis usually observed with ordinary strains of PVY (PVYO) in this variety. Isolate AL1 was obtained from tubers of potato cv. Alturas showing distinct internal light brown rings and blotches. When RR1 and AL1 were transmitted to tobacco (Nicotiana tabacum L. cvs. Samsun NN and 423), they caused systemic veinal necrosis, including stem and petiole lesions typical of PVYN strains (2). Symptoms induced by RR1 and AL1 on tobacco appeared 9 to 11 days after inoculation, whereas some other isolates caused delayed veinal necrosis. All isolates that produced veinal necrosis on tobacco were detectable with PVY polyclonal antisera. Potato virus X was not detected by enzyme-linked immunosorbent assay in tobacco plants showing veinal necrosis. Some isolates, including AL1, failed to react in serological tests using PVYN-specific monoclonal antibodies obtained from three commercial sources. Other isolates, including RR1, were detectable with these monoclonal antibodies. Reverse transcription-polymerase chain reaction (RT-PCR) products obtained with primers specific for the coat protein (CP) open reading frame (ORF) were cloned and sequenced. AL1 possesses a CP more closely related to PVYO type isolates, which would account for its failure to react with PVYN monoclonal antibodies. In this regard, AL1 is similar to the PVYN-Wilga isolate (1). Other isolates that are detectable with the PVYN monoclonal antibodies possess a CP more consistent with N strains of the virus. Results of RT-PCR tests using primers derived from the P1 ORF sequence (3), and the restriction enzyme analysis and sequencing of the RT-PCR products, all suggest that AL1 and RR1 are related to European-type members of PVY tuber necrotic (NTN) or N strains. However, other isolates under investigation appear to be more closely related to previously reported North American NTN types (3). The symptomatology of these viruses on tobacco and potato, and the serological and molecular data clearly show that at least two distinct variants of PVYN have been found for the first time in a major potato production area of the United States, and pose a potential threat to the potato industry. References: (1) B. Blanco-Urgoiti et al. Eur. J. Plant Pathol. 104:811, 1998. (2) J. A. de Bokx and H. Huttinga. Potato virus Y. Descriptions of Plant Viruses. No. 242, CMI/AAB, Surrey, England, 1981. (3) R. P. Singh et al. Can J. Plant Pathol. 20:227, 1998.

Four classes of plant growth regulators were tested for their effects on Verticillium wilt (Verticillium dahliae) of potato (Solanum tuberosum L.). These substances had auxin, cytokinin, gibberellin, or growth retardant activity. Preliminary greenhouse experiments were conducted to screen materials for effectiveness and to determine suitable application rates. A series of field experiments was then conducted over a four year period. The auxin, napthalene acetic acid, consistently reduced wilt and stem colonization byV. dahliae both in the field and in the greenhouse. Indole acetic acid was only partially effective at reducing wilt and stem colonization, possibly due to its labile nature. Other growth regulators, benzyladenine, (a cytokinin), gibberellic acid — A3 (a gibberellin), chlorflurenol and daminozide (growth retardants), either had no consistent effect or increased wilt and stem colonization. The effect of auxins on wilt reduction was observed in the highly susceptible cultivar Norgold Russet, the moderately susceptible Russet Burbank, and the highly resistant selection A66107-51. Although napthalene acetic acid significantly reduced wilt severity (up to 50%) in field grown Russet Burbank, the reductions in stem colonization byV. dahliae were not of the same magnitude as seen when comparing the highly resistant selection A66107-51 with a susceptible clone. Growth regulator treatments that suppressed wilt or stem colonization did not increase total yield and generally resulted in tuber malformations.

The relationship of potato (cv. Russet Burbank) tuber stem-end discoloration to speed of vine kill and maturity of vines when killed was studied for three years at several sites in Idaho. Discoloration due to leafroll was separately determined. Vine killing with sulfuric acid, dinoseb, endothall and hand pulling produced a range in killing speeds from fast to slow. Vine kill speed alone did not affect amounts of discoloration. Vines that died naturally from frost or other causes had as much discoloration (14% over all treatments) as from any chemical or mechanical vine killing method. The tendency for tuber discoloration increased when vines were less mature when killed.