Foliar and tuber assessment of late blight (Phytophthora infestans (Mont.) de Bary) reaction in cultivated potato (Solanum tuberosum L.)

Summary Host plant resistance is an important component to the management of potato late blight,Phytophthora infestans (Mont.) de Bary. Assessment of potato lines (Solanum tuberosum L.) with various levels of resistance toP. infestans (US8, A2 genotype) were evaluated in field trials, greenhouse controlled environment chambers and inoculated tuber reactions. Five lines (AWN86514-2, B0692-4, B0718-3, Jacqueline Lee, and B0288-17) with strong foliar resistance to late blight were identified in these inoculated field trials. Greenhouse controlled environment chamber studies allowed resistant and susceptible lines to be distinguished, but the 1998 greenhouse results did not correlate well with field data. Four lines (A084275-3, Bzura, MSG007-1, and MSG297-4RD) evaluated by a digital image analysis technique demonstrated tuber resistance based upon average reflective index values in the inoculated tuber studies. Tuber resistance did not correlate with field foliar resistance. Based upon these results, field assessment of foliar reaction toP. infestans provides the best measure for assessing late blight resistance in potato. Tuber resistance to late blight can be identified among lines with varying levels of foliar resistance.     

Susceptibility of potato varieties and advanced breeding lines (Solanum tuberosum L.) toPhytophthora infestans (Mont.) de Bary in greenhouse screenings

Late blight (Phytophthora infestons (Mont.) de Bary) has re-emerged as an important pathogen of the cultivated potato (Solanum tuberosum subsp.tubero-sum L.) in North America. The purpose of this study was to evaluate the relative susceptibility of potato germplasm in the greenhouse in order to initiate a breeding program for resistance to the US-8/A2 mating type which is the more aggressive and prevalent strain of late blight. Whole plants of 147 cultivars and breeding lines were evaluated. Percent plant area infection was visually assessed. Seven days after inoculation, infection ranged from 0 to 100% and the overall mean was greater than 50%. Two-thirds of the cultivars and breeding lines tested were very susceptible to the US-8 genotype. The highest resistance was identified in the somatic hybrids betweenS. tuberosum andS. bulbocastanum and their backcross derivatives. Pike and Snowden were less susceptible than the other North American cultivars. Zarevo was most resistant among the European cultivars. Seven of the advanced breeding lines were equivalent to Zarevo in infection levels. The host plant resistance identified among the material tested in this study can be used by breeding programs to develop improved cultivars with resistance to US-8 genotypes of late blight.     

Defender: A high-yielding, processing potato cultivar with foliar and tuber resistance to late blight

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.     

Relationship between resistance to late blight in potato foliage and tubers of cultivars and breeding selections with different resistance levels

Due to changes in the pathogen population, late blight of potatoes caused byPhytophthora infestans has become a more difficult disease to manage and there is a need for new potato cultivars with greater and more stable disease resistance. Field studies are required to identify and characterize host resistance to late blight in both foliage and tubers but, as epidemics vary from year to year, combining multi-year results can be difficult. Residual maximum likelihood (REML) was successfully used to analyze data which demonstrated good correlations between foliar and tuber responses to late blight (US-1 genotype). In addition, studies on post-harvest inoculated tubers provided more reliable disease responses than field studies, and the disease resistance with this method correlated well with foliar disease responses. This tuber test would be a useful method of pre-screening selections for disease response prior to testing in the field.     

Foliar reaction toPhytophthora infestans in inoculated potato field trials in Michigan

Late blight, caused byPhytophthora infestans, is the most important disease of potato worldwide and foliar resistance is an important component of managing late blight in the field. The objective of this research was to identify germplasm for use in breeding cultivars with foliar resistance toP. infestans. More than 500 clones were tested from 1997 to 2002 in inoculated (US8 genotype) field experiments conducted at the Michigan State University Muck Soils Research Farm in Bath, Michigan. All of the current commercial cultivars tested were classified as susceptible toP. infestans. The most resistant clones were A90586-11, AWN86514-2, B0718-3, Jacqueline Lee (MSG274-3), MSI152-A, MSJ307-2, MSJ317-1, MSJ453-4Y, MSJ456-2, MSJ456-4, MSJ461-1, MSK101-2, MSK128-1, NY121, LBR8, LBR9, Tollocan, and Torridon. Some of these resistant selections were from crosses with B0718-3, Jacqueline Lee, and Tollocan suggesting that the resistance toP. infestans was transmissible. These resistant clones will provide the opportunity to breed late-blight-resistant cultivars from a diverse pool of cultivated germplasm. Consistent foliar reaction toP. infestans over years suggested that the Michigan State University Muck Soils Research Farm is a valuable location for North American breeders to assess the reaction of potato germplasm to the US8 genotype of late blight.     

Assessment of field responses of potato cultivars and breeder seedlings to potato late blight epidemics

The response to potato late blight of 116 potato cultivars and breeding lines was determined in replicated trials conducted between 1980 and 1988. The index of area under the standardized disease progress curve (ASDPC), based on the cultivar Sebago, was used to rank the cultivars and to identify cultivars that had inconsistent disease responses over years. Most of the cultivars were susceptible to late blight; only 10 cultivars out of 66 currently available (including breeding lines) were judged more resistant than Sebago. Nine cultivars were identified as having inconsistent resistance over years. The index ASDPC was less variable than the relative area under the disease progress curve when the yearly disease conditions differed from the normal.     

Glycoalkaloid content inSolanum species and hybrids from a breeding program for resistance to late blight (Phytophthora infestans)

As part of an effort to study the relationship between the “glycoalkaloid trait” and genetic resistance to late blight (Phytophthora infestans), glycoalkaloid content in tuber and foliar tissues from a wide genetic background withinSolanum, includingS. demissum, S. iopetalum and 15 hybrids selected from a backcrossing breeding scheme was determined. Analysis of variance indicated significant genotypic effect on total glycoalkaloid, solanidine, α-solanine, and α-chaconine content in both tubers and leaves. Tubers from wild potato species commonly contain glycoalkaloids in concentrations that exceed international health regulations for human consumption (20 mg/100 g fresh weight). In this study,S. demissum andS. iopetalum were highest in total tuber glycoalkaloids among all materials tested, with 70.4 and 76.2 mg/100 g fresh weight, respectively. In contrast, both commercial cultivars had the lowest concentration, both below the safety limit. Solanine was more abundant than chaconine in all but one genotype. All hybrids were intermediate to low in total glycoalkaloids. Except for the two wild species, glycoalkaloid concentration in leaves of all genotypes studied was at least twice that in tubers, with glycosylated forms accounting for more than 80% total glycoalkaloid content. Correlation between tuber and foliage alkaloids was poor. In view of the observed field resistance to late blight, it was concluded that tuber glycoalkaloid content may not be responsible for such resistance.     

Impact of Agronomic Strategies (Seed Tuber Pre-sprouting,Cultivar Choice) to Control Late Blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>) on Tuber Growth and Yield in Organic Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) Crops

In order to optimize potato crop management in organic farming systems, knowledge of crop growth processes in relation to limitations and reductions by nitrogen (N) and disease is necessary. This paper examines the effect of different prevention measures (seed tuber pre-sprouting, choice of cultivars: resistance to Phytophthora infestans; earliness of tuber initiation) against disease-related constraints on yields, depending on the N-mediated growing conditions of organic potato crops. Under conditions of a relatively high N supply, accelerating the early development and tuber initiation of potato crops by seed tuber pre-sprouting (yield increase of c. 18–23%) or the selective choice of cultivars with an earlier tuber initiation (yield increase of c. 0–21%) are the most effective strategies in combating late blight. They bring forward the crop development c. 7–10 days, escaping the negative impact of the fungus on tuber growth. Under conditions of a relatively low N supply, these strategies do not affect final tuber yield. The reason for the differences of the effect depending on N supply of the crops is, that the lower the N supply, the shorter the period of time over which tuber growth takes place, independent of whether P. infestans becomes severe or not. Tuber growth of organic crops low in N has mostly ceased by the time late blight becomes potentially important for limiting yield, with the consequence that preventative measures against P. infestans are meaningless. Surprisingly, the level of cultivar haulm resistance to late blight did not affect tuber yields in years with an early and strong late blight development. Probably, the positive effect of a longer resistance to the fungus (c. 1 week) was counterbalanced by a later tuber initiation (also c. 1 week). In years with a moderate late blight incidence, less susceptible cultivars were able to produce higher tuber yields on fields with a lower N availability (c. 17–20%), probably due to higher N use efficiency and a better match of N mineralization and N uptake. Under conditions of a relatively high N supply, the tested cultivars with a higher haulm resistance to late blight were not able to improve tuber yields.     

Breeding Potential of Potato Somatic Hybrids: Evaluations for Adaptability,Tuber Traits,Late Blight Resistance,Keeping Quality and Backcross (BC<Subscript>1</Subscript>) Progenies

Ten tetraploid interspecific potato somatic hybrids developed earlier through protoplast fusion between the dihaploid Solanum tuberosum L. ‘C-13’ and the diploid wild species Solanum pinnatisectum Dun. were used in this study. Somatic hybrids and standard control cultivars were evaluated for adaptability, tuber traits, late blight resistance and keeping quality attributes (dormancy, sprouting, weight loss and appearance after 75 days of storage) during two successive winter crop seasons (short-days) in the sub-tropical plains of India, where nearly 90% of India’s potatoes are grown. Somatic hybrids showed medium to good plant vigour and late to very late plant maturity. Though none of the somatic hybrids produced equal or higher tuber yield than the control cultivars, except clone P7, all other somatic hybrids produced significantly higher marketable and total tuber yield after a 90-day growth than the parent C-13. Most of the somatic hybrids possessed higher tuber dry matter concentration, resistance to late blight and better keeping quality attributes than the control cultivars. Notably, the tubers of somatic hybrids showed a tendency for colour change from white to purple on exposure to sunlight. Breeding potential of somatic hybrids was further assessed by crossing them with commonly grown local potato cultivars for the development of backcross (BC₁) progenies. In the hybridization programme, berries were formed while somatic hybrids were used either as male or female parents with common cultivars. Our results revealed that the use of bulk pollen of somatic hybrids not only resulted in higher pollination success but also helped to achieve higher numbers of true potato seeds (TPS) per berry. Despite the formation of berries, TPS was absent in 22 crosses using somatic hybrids as a female or male parent which may be due to ovule or embryo abortions. Segregating BC₁ generations were evaluated under the same sub-tropical conditions for further exploitation in potato breeding. Based on our study, the somatic hybrids P4, P8 and P10 can be utilized for the introgression of important characters such as high tuber dry matter concontration, resistance to late blight and excellent keeping quality attributes into the cultivated potato via conventional breeding methods for cultivar development in the sub-tropical plains of India.     

Potassium phosphite combined with reduced doses of fungicides provides efficient protection against potato late blight in large-scale field trials

Potato late blight caused by the oomycete Phytophthora infestans is a devastating disease of potato worldwide. Most of the potato cultivars grown in conventional agriculture are susceptible, or at best moderately resistant, and require frequent applications of fungicides to avoid heavy yield losses.In field trials spanning four years, we have investigated the effect of potassium phosphite, an inorganic salt on potato late blight. Potassium phosphite is known to induce defence responses in potato and to also have direct toxic effects on oomycetes, which in turn counteract late blight and tuber blight development. However, the use of this salt is not yet implemented and approved in European potato cultivation. We compared the effect of phosphite alone with fungicides currently used in Swedish potato cultivation. We also investigated the combined use of potassium phosphite and reduced doses of fungicides. Table potato cultivars and starch potato cultivars with different levels of resistance were used.We found that potassium phosphite in combination with reduced doses of fungicides results in the same level of protection as treatments with the recommended full dose of fungicides. These combined treatments reduce the need of traditional fungicides and may also decrease the selection pressure for fungicide resistance development in the pathogen. In relatively resistant starch potato cultivars using phosphite alone gave sufficient protection against late blight. Furthermore, in starch potato a combination of phosphite and fungicides at two-week intervals provided similar protection to weekly applications of fungicide at the recommended dose. Foliar treatment with phosphite also gave protection against tuber blight at similar levels to that of the best-performing fungicide. Our data suggests that potassium phosphite could be used in potato cultivation in temperate regions such as in Sweden, at least in combinations with reduced rates of fungicides. The implementation of the use of phosphite in practical potato crop protection as part of an IPM strategy is discussed. Doses, intervals and combinations could be adjusted to the level of cultivar resistance.     

Effects of pest and soil management systems on potato diseases

Long-term cropping systems research is important in order to reduce production costs, to control crop pests, and to optimize the sustainability of agro-ecosystems. Soil amendment use, improved disease management practices, and careful cultivar choice are some of the potential components for improving potato production systems. This research was conducted in long-term cropping systems plots in order to evaluate the impact of soil amendments, pest management practices, and cultivar on foliar and soil-borne potato diseases and to assess the relationships of soil and pest management practices to disease levels and soil microbial activity. Fungicide applications for management of foliar diseases varied between the pest management systems (e.g., biological, reduced input, and conventional). Incidence of potato foliar diseases was quantified five times during the cropping season. The impact of soil amendment and pest management practices on soil microbial activity and tuber-borne diseases was also investigated. Low incidences of foliar and selected soil-borne diseases were recorded. Disease levels varied between years, cultivars, pest management, and soil amendments. Significant differences between cultivars were detected for early blight, white mold, and black dot. The cultivar Superior had higher incidence of white mold and black dot, while cv Atlantic had higher early blight incidence. Pest management system significantly affected foliar early blight incidence in 1998, but not in 1997. Pest management system did not affect late blight, white mold, or black dot incidence, or tuber disease incidence in either year. The addition of soil amendments significantly impacted tuber black dot incidences. Microbial activity responded to increasing temperature as the season progressed and was significantly enhanced by the addition of manure and compost soil amendments; however, lower disease incidence was not associated with increased microbial activity. While pest management practices were not major determinants of disease levels in these experiments, the results show that soil amendments can increase incidence of selected tuber diseases and microbial activity in soils.     

Light use efficiencies of potato cultivars with late blight (Phytophthora infestans)

Summary Potato cultivars of different maturity classes and levels of resistance toPhytophthora infestans were grown under several disease intensities in three field trials. Seasonal courses of ground cover by green foliage and final tuber yields were determined. Light use efficiencies (LUE) were calculated from regression analyses of yield on cumulative light interception. Late blight reduced tuber yields by decreasing cumulative light interception without affecting LUE. No differences in LUE between cultivars or cultivar classes were detected. Therefore, the maintenance of green leaf area is important when breeding potatoes for optimal performance in the presence of late blight. The results support the hypothesis that the correlation between lateness and reported resistance of potato cultivars is due to the vigorous foliage growth of late cultivars.     

Assessment and analyses for the interpretation of potato late blight response in field studies

Potato seedlings and cultivars were successfully subjected to moderate to heavy late blight pressure in field plots to which a race complex of the pathogen was applied. Multiple assessments through the course of the epidemics revealed differences in overall disease susceptibility or resistance. Differences were also demonstrated in disease response patterns among potato lines with similar overall disease ratings. Use of principal component and cluster analyses established discrete groupings of potato lines. This provides a basis for a more objective interpretation of the results in identifying both overall disease response and pattern (slow or fast) of response of potato cultivars and breeding lines.     

Payette Russet: a Dual-Purpose Potato Cultivar with Cold-Sweetening Resistance,Low Acrylamide Formation,and Resistance to Late Blight and Potato Virus Y

Payette Russet is a full season, russet-skinned potato cultivar notable for its cold-sweetening resistance and associated low acrylamide formation, making it ideally suited for processing into French fries and other potato products. Low asparagine and reducing sugar concentrations in Payette Russet tubers contribute to an 81 % reduction in acrylamide content in French fries relative to cultivars Ranger Russet and Russet Burbank following eight months storage at 9 °C. In three years of evaluations in the Western Regional Potato Variety Trials, average yield of Payette Russet was intermediate between Ranger Russet and Russet Burbank, but Payette Russet had the highest U.S. No. 1 yield when averaged across all eight trial locations. Acceptably low tuber glucose concentrations (<0.10 % glucose FWB) were maintained in Payette Russet following up to nine months storage at temperatures as low as 5.6 °C with consistently acceptable French fry color scores obtained (USDA value ≤2.0). Reducing sugars are also maintained uniformly throughout Payette Russet tubers, resulting in a low incidence of sugar ends and reduced mottling in French fries relative to standard processing cultivars. Long tuber dormancy also benefits long-term storage for processing. With its russet skin, Payette Russet could also be used for fresh-pack, and its assemblage of disease resistances makes it especially suitable for organic production, or for use by growers and companies seeking greater sustainability in their production. Payette Russet is resistant to foliar and tuber late blight, common scab, and has extreme resistance to PVY conferred by the presence of the Rysto resistance gene. Payette Russet also has a moderate level of resistance to Verticillium wilt, early blight, and corky ringspot. It is susceptible to Fusarium dry rot (F. sambucinum), therefore production and storage management guidelines are provided to minimize tuber infection. Payette 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 Payette Russet is similar to Russet Burbank and reduced relative to Ranger Russet. Payette Russet was more susceptible to shatter bruise, internal brown spot, and tuber weight loss in storage relative to the industry standard cultivars. Payette Russet was released in 2015 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Northwest (Tri-State) Potato Variety Development Program.     

The Relationship Between Active Oxygen Metabolism and Resistance to Late Blight in Potato

The relationship between active oxygen metabolism and resistance to late blight (Phytophthora infestans) in potato (Solanum tuberosum L.) was studied for 72 h post-inoculation by comparing three resistant cultivars (low disease index) with three susceptible ones (high disease index). Activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), and the content of ascorbic acid (ASA), were higher in the resistant cultivars than in the susceptible ones. The production rate of the superoxide anion radical (O₂^?) was lower in the resistant cultivars than in the susceptible ones. These changes, which were associated with the potato plant’s response to infection with P. infestans, provide some insight into the physiological basis of resistance and may also provide a screening tool for resistance to late blight.     

The Effect of Long Term Storage on Bacterial Soft Rot Resistance in Potato

Bacterial soft rot is a serious disease in potato (Solanum tuberosum L.), causing rapid tuber tissue maceration and, consequently, marketable yield loss. Soft rot bacteria, including Pectobacterium carotovorum subsp. carotovorum (Pbc), are favored by moist conditions, which are prevalent in large potato storage facilities. However, although most potatoes in North America are stored before use, there are no published surveys of soft rot resistance in cultivars exposed to long-term storage conditions. Thus, we tested 65 cultivars and 13 breeding lines for soft rot resistance after 6 months of storage. There was a significant effect of cultivar and production environment on soft rot resistance score. During 6 months of storage, tuber soft rot resistance in resistant clones did not change, while it changed in susceptible clones. The three most resistant cultivars to soft rot were Freedom Russet, Anett, and Alaska Red Eye.     

Wallowa Russet: A full season long Russet for processing and fresh market

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.     

Elkton: A New Potato Variety with Resistance to Internal Heat Necrosis and Hollow Heart and Suitable for Chipping Directly from the Field in the Southern United States

Elkton is a medium to medium-late maturing potato variety with tan netted-skin, round-oval tubers, and white-flesh. Average marketable yields ranged from 76 % to 113 % of Atlantic and average specific gravities ranged from ?0.002 to ?0.006 less than Atlantic depending on location. Chip color processed directly from the field in southern locations or from storage in the northern locations is equivalent to Atlantic. Elkton is resistant to internal heat necrosis and hollow heart. Color and texture ratings of Elkton following baking, boiling and microwaving have been similar to Atlantic. Elkton is moderately resistant to early blight and Verticillium wilt; moderately susceptible to foliar late blight and susceptible to tuber late blight; moderately susceptible to powdery scab; and, susceptible to potato virus Y and potato virus S. Its reaction to common scab has been inconsistent. Plant Variety Protection has been requested for Elkton.     

Alturas: A multi-purpose, Russet potato cultivar with high yield and tuber specific gravity

‘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.