Haplotypes of the Potato Psyllid, Bactericera cockerelli, on the Wild Host Plant, Solanum dulcamara, in the Pacific Northwestern United States

‘Candidatus Liberibacter solanacearum’ (Lso) is a bacterium that infects solanaceous crops and causes plant decline and yield losses, especially in potato and tomato. Lso is transmitted to these hosts by the potato psyllid (Bactericera cockerelli Sulc) vector. B. cockerelli host plants are not limited to crop plants, but also include many wild, solanaceous weeds. These wild hosts could potentially impact overwintering and breeding of the psyllids and serve as reservoirs for Lso. In the Pacific Northwestern United States, B. cockerelli was recently reported to overwinter on bittersweet nightshade (Solanum dulcamara L.). The present study utilized high resolution melting analysis of the B. cockerelli mitochondrial cytochrome c oxidase I gene to assess the psyllid populations occurring on S. dulcamara during the summer and winter months in Washington, Oregon, and Idaho. This technique has previously been used to analyze the cytochrome c oxidase I gene of B. cockerelli, and has identified four psyllid haplotypes. Lso infection was also determined for the psyllids collected from S. dulcamara. During both the summer and the winter months in the Pacific Northwest, the Northwestern psyllid haplotype was the predominant population found living on S. dulcamara. However, low levels of the Western psyllid population were also present in Washington and Oregon during the same period. No overwintering psyllids tested were Lso-infected, suggesting that these populations do not pose an imminent threat of Lso transmission to newly emerging potatoes and other solanaceous crops in the region, unless a source of Lso becomes available.     

Development of a PCR Assay for the Rapid Detection and Differentiation of ‘Candidatus Liberibacter solanacearum’ Haplotypes and Their Spatiotemporal Distribution in the United States

Zebra chip, or zebra complex (ZC) has become an important invasive disease of potato in the United States and New Zealand and is caused by a phloem-limited bacterium, ‘Candidatus Liberibacter solanacearum’ (Lso). A PCR assay using a single pair of simple sequence repeat (SSR) primers was developed for simultaneous detection and genotype differentiation of Lso haplotypes associated with zebra chip disease of potato. The sensitivity of the SSR PCR was similar to a 16S PCR assay, with detection limit of 100 copies of the Lso genome in haplotype A infected potato and psyllid samples and 10 copies of Lso genome in haplotype B potato and psyllid samples. The Lso detection frequency of the SSR PCR assay was 79.1 % in potato and 26.4 % in psyllid samples, respectively; whereas the detection frequency of the 16S PCR assay 59.0 % in potato and 25.9 % in psyllid samples, respectively. Samples of Lso positive potato plants and psyllids from multiple states in the US were demonstrated to have either haplotype A or haplotype B Lso and occasionally both haplotypes were found in individual samples. This is the first report that co-infection of the two haplotypes of Lso exists in potato and potato-psyllid samples. Only haplotype A Lso was detected in North Dakota psyllid samples collected in 2010, in Idaho and Washington ZC potato samples sampled from storage in 2011, and in Idaho ZC potato samples in 2012. Haplotype A Lso was also detected in New Zealand ZC affected potato samples and psyllid samples collected in 2010 and 2011. The PCR assay developed is as sensitive as previously developed assays and has the advantage of simultaneously detecting and differentiating Lso haplotypes of the ZC bacterium, thus making it extremely useful for epidemiological studies.     

First Report of Potato Psyllids, Bactericera cockerelli, Overwintering in the Pacific Northwest

Potato psyllids became a topic of interest at the end of the 2011 growing season in the Pacific Northwest when they were first documented to transmit ‘Candidatus Liberibacter solanacearum,’ the putative pathogen causing zebra chip disease in the region. Zebra Chip is characterized by above and below ground symptoms that cause significant yield loss. For many decades it has been unclear whether the potato psyllid migrates to states in the Pacific Northwest from large, well-documented infestation areas in California or Texas. Thus, we conducted a study in the spring of 2012 in the lower Columbia Basin (north east Oregon and south east Washington state), and in the fall, winter, and spring of 2012 in southwestern Idaho to determine if psyllids could be found overwintering. Potato psyllid was observed in November 2011 in southwestern Idaho and March 2012 in the lower Columbia Basin living on Solanum dulcamara L. (i.e., bittersweet nightshade), a perennial weed of wet habitats and riverbanks. Potato psyllids were collected and brought to the laboratory. Emerging adults from both locations (i.e., Columbia Basin and Idaho) were offered potato plants and they completed a second generation in approximately 15 days under similar environmental conditions. While overwinter survival of the potato psyllid in the Pacific Northwest is concerning for the potato industry, weather trends in the region were mild during the winter of 2012. It is unknown whether a colder or longer winter season would affect the overwintering biology we have observed. Observations through several coming winters are warranted.     

Association of Potato Psyllid (<Emphasis Type="Italic">Bactericera cockerelli</Emphasis>; Hemiptera: Triozidae) with <Emphasis Type="Italic">Lycium</Emphasis> spp. (Solanaceae) in Potato Growing Regions of Washington,Idaho, and Oregon

Potato psyllid, Bactericera cockerelli (?ulc), causes economic damage to potato crops throughout the major potato growing regions of western North America. When cultivated crops are not available, potato psyllid often occurs on non-crop hosts. In the southern U.S. and northern Mexico, native species of Lycium (Solanaceae) are important non-crop hosts for the psyllid. We determined whether Old World species of Lycium now widespread in the Pacific Northwest are reservoirs of potato psyllid in this growing region. We examined Lycium spp. across a wide geographic region in Washington, Oregon, and Idaho at irregular intervals during three growing seasons. Potato psyllids were present at all locations. To determine whether Lycium is also a host during intervals of the year in which the potato crop is not available, we monitored a subset of these sites over the entire year. Six sites were monitored at 1- to 3-week intervals from June 2014 to June 2016. Psyllids were present on Lycium throughout the year at all sites, including during winter, indicating that Lycium is also a host when the potato crop is seasonally not available. Psyllid populations included a mixture of Northwestern and Western haplotypes. We observed well-defined spring and fall peaks in adult numbers, with peaks separated by long intervals in which psyllid numbers were very low. Seasonal patterns in psyllid numbers on these non-native Lycium hosts were very similar to what has been observed on native Lycium in the desert southwest region of the U.S. Our findings demonstrate that potato psyllid associates with Lycium across a broad geographic region within the Pacific Northwest. These results will assist in predicting sources of potato psyllid colonizing potatoes in this important growing region.     

Economic Impacts of Zebra Chip in Idaho,Oregon, and Washington

Zebra Chip disease vectored by the potato psyllid Bactericera cockerelli (?ulc) was first reported in Idaho and the Columbia Basin of Oregon and Washington in 2011. Since then growers have incurred significant costs for managing the disease. Thus, we conducted an expert opinion survey to estimate expenditure on insecticides dedicated to controlling potato psyllids in the largest potato producing regions of Idaho, Oregon, and Washington. Results highlight a total of about 9 million US dollars spent on active ingredients targeted at psyllid control. When application costs are added to the cost of insecticides, expenditures total about 11 million US dollars.     

Role of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ and <Emphasis Type="Italic">Bactericera cockerelli</Emphasis> Haplotypes in Zebra Chip Incidence and Symptom Severity

Two haplotypes of the pathogen, ‘Candidatus Liberibacter solanacearum,’ (Lso) and four haplotypes of the insect vector, Bactericera cockerelli, are associated with zebra chip disease of potato. Whether disease severity or incidence is influenced by pathogen or insect haplotype is poorly understood. The role of Lso ‘A’ and ‘B,’ transmitted by three haplotypes of B. cockerelli, on disease severity and incidence in eight potato cultivars was analyzed. Both haplotypes of Lso induced tuber symptoms. In general, Lso B caused higher incidence of symptoms, and greater reduction in tubers compared with Lso A. Lso B was associated with more severe tuber symptoms, producing fewer mild or moderate tuber symptoms. Lso A was associated with less severe tuber symptoms, despite being able to induce severe symptoms. Disease incidence, tuber yield, and symptom severity ratings were not dependent upon the psyllid haplotype transmitting the pathogen, suggesting that pathogen, not insect haplotype affects Lso transmission.     

Characterization of the Tolerance against Zebra Chip Disease in Tubers of Advanced Potato Lines from Mexico

Potato zebra chip disease (ZC), a threat to potato production in the USA, Mexico, New Zealand, and Central America, is associated with the bacterium “Candidatus Liberibacter solanacearum” (Cls) that is vectored by the potato psyllid (Bactericera cockerelli Sulc.). ZC control currently depends on insecticide applications, but sustainable control will require development of resistant and/or tolerant varieties. This study characterized four promising potato lines (246, 865, 510 and NAU) exposed to Cls-positive adult psyllids in choice and no-choice assays for ZC resistance. Psyllids preferred to settle on Atlantic over 246 and 865, and oviposit on Atlantic compared to 510. However, tolerance to ZC appeared more dependent on host responses to Cls infection. All four of these potato genotypes exhibited putative ZC tolerance in raw tubers compared to the susceptible commercial variety Atlantic. Expressed tolerance was associated with reduced concentrations of phenolic compounds in Cls-infected raw tubers with corresponding reductions in freshly-cut symptoms. However, these four genotypes exhibited ZC-linked discoloration of fried tuber slices, which was associated with increased sugar content that occurred following Cls-infection. As a result, these four ZC-tolerant experimental potato lines could be useful if the tubers produced are used for fresh, but not processing, markets.     

Carrot Pathogen ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ Haplotype C Detected in Symptomless Potato Plants in Finland

‘Candidatus Liberibacter solanacearum’ (CLso) haplotype C, a bacterial pathogen transmitted by the carrot psyllid Trioza apicalis, causes yield losses in carrot production. Due to concerns that this pathogen might also threaten potato (Solanum tuberosum) production, the occurrence of CLso in cultivated and volunteer potatoes in Tavastia Proper and Satakunta regions of Finland was studied. Volunteer potato plants were found in 13 of the 27 inspected carrot fields. Of the 148 potato samples tested by PCR, eight volunteer potato plants and one cultivated potato grown at the edge of a carrot field were found to be CLso positive. The PCR products obtained from these potatoes with primers OA2/OI2c, LpFrag4-1611F/LpFrag4-480R and CL514F/CL514R all showed 100% sequence identity to CLso haplotype C. This is the first observation of CLso haplotype C in field-grown potatoes. In addition, transmission experiments were performed. Attempts to transmit CLso into potato with carrot psyllids were not successful; however, CLso haplotype C was transmitted from infected carrots to potato plants by leaf grafting and by phloem connection formed by dodder, a parasitic plant, and found to survive in the potato plants for several weeks after transmission. However, the bacterial colonisation progressed slowly in the potato phloem and the amount of bacteria detected was low. The plants produced from the daughter tubers of the CLso-positive potato plants were all CLso negative, suggesting that CLso haplotype C was not able to pass to the daughter plants. None of the CLso-positive potatoes inoculated in greenhouse or collected from fields showed symptoms characteristic of zebra chip disease, associated with CLso haplotypes A and B.     

Teton Russet: An Early-Maturing,Dual-Purpose Potato Cultivar Having Higher Protein and Vitamin C Content,Low Asparagine,and Resistances to Common Scab and Fusarium Dry Rot

Teton Russet is an early-maturing, medium-russeted, potato cultivar with high merit for both fresh-pack and processing. In early harvest trials in the Pacific Northwest, Teton Russet had total yields similar to Russet Norkotah, and higher than Ranger Russet and Russet Burbank. Marketable yield of Teton Russet in the early harvest trials was also comparable to or higher than Russet Norkotah in Washington and Oregon, and higher than Ranger Russet and Russet Burbank at these sites, as well as in Idaho. In full-season trials, while total yield of the earlier-maturing Teton Russet tended to be lower than Ranger Russet and Russet Burbank, marketable yield was generally higher than Russet Burbank across the majority of sites due to its higher percentage of U.S. No. 1 tubers. Teton Russet is suitable for processing, with acceptable fry color following up to 8 months of storage at 8.9 °C. Uniformity of fry color was also very consistent. Teton Russet has shown lower levels of the amino acid asparagine relative to Ranger Russet and Russet Burbank which may contribute to lower acrylamide levels in French fries and other processed potato products. Teton Russet is notable for having resistance to common scab (Streptomyces spp.) and Fusarium dry rot, and is moderately resistant to tuber net necrosis. Analyses have also shown Teton Russet to have significantly higher protein levels than Russet Norkotah, Ranger Russet, and Russet Burbank, as well as higher vitamin C content than Russet Norkotah and Russet Burbank. Teton 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.     

Behavioral responses of adult potato psyllid, Bactericera cockerelli (Hemiptera: Triozidae), to potato germplasm and transmission of Candidatus Liberibacter psyllaurous

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is a major pest of potatoes that can cause yield loss by direct feeding on crop plants and by transmitting a bacterial pathogen, Candidatus Liberibacter psyllaurous (a.k.a. Candidatus Liberibacter solanacearum) associated with zebra chip disease of the crop. In recent years, there have been no studies regarding resistance of potato to the potato psyllid or the bacterial pathogen that the psyllid transmits. Thus, the objectives of this study were to determine the effects of potato germplasm on adult potato psyllid behavior and transmission of Ca. L. psyllaurous. A total of twenty-two potato (Solanum tuberosum L.) breeding clones and varieties were examined. Plant genotype significantly affected the occurrence and duration of psyllid probing, the duration of psyllid cleaning, resting and the amount of time psyllids spent off the potato leaflet as well as transmission of Ca. L. psyllaurous. For the potato genotypes in which there were significant decreases in transmission compared to controls, there was often an unclear relationship between the occurrences and duration of behaviors and subsequent bacterial transmission. We discuss the implications of our results for an integrated pest management program for the potato psyllid and Ca. L. psyllaurous control on potatoes.     

Gemchip: A new potato variety with chipping quality and verticillium resistance for the Western U.S.

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.     

Gem russet: A long russet potato variety with excellent fresh market and french fry processing quality

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.     

Western russet: A new potato variety with excellent fresh market and frozen-fried processing quality and field resistance to common scab and PVYo

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 PVY^o, 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.     

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

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

Winema: An Early Maturing, Red- Skinned Cultivar for Fresh Market

Winema, an early maturing, red-skinned cultivar for fresh market use, was jointly released in 2000 by the Agricultural Experiment Stations of Oregon, North Dakota, California, Idaho, and Washington. Winema was evaluated in irrigated trials in Oregon and California from 1990 to 2000 and in the Western Regional Trial in 1995,1997, and 1998. Winema has produced lower total yields than Dark Red Norland and Red LaSoda at most locations, but similar or higher marketable yields and significantly fewer culls. In 20 location-years of replicated Oregon and California trials, Winema produced 108% and 99% of marketable yields of tubers under 280 g compared with Red LaSoda and Dark Red Norland, respectively. Similarly, in 23 location-years of The Western Regional Trial in 6 western states, Winema produced 109% and 92% of marketable yields of tubers under 280 g compared with Red LaSoda and Dark Red Norland, respectively. Winema tubers are smooth-skinned with shallow eyes. Winema’s bright red color does not fade appreciably in storage. Winema is susceptible to potato virus Y (PVY). Foliar symptoms of PVY are difficult to detect visually.     

Ivory Crisp: A potato variety with high tuber solids and cold chipping ability

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.     

Characterizing Zebra Chip Symptom Severity and Identifying Spectral Signatures Associated with ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’-Infected Potato Tubers

Zebra chip (ZC) disease has been a threat to the US potato industry for nearly two decades. ZC is associated with the bacteria ‘Candidatus Liberibacter solanacearum’ (Lso), which is transmitted by the potato psyllid, Bactericera cockerelli (?ulc) (Hemiptera: Triozidae). ZC reduces yield and quality, due to discoloration of the tuber tissue. Symptom severity is affected by the time of infection and early-season infections express relatively higher degrees of ZC. Although tubers infected late in the growing season, i.e. within 2 weeks of harvest, express minimal to no symptoms, they may proceed to express ZC symptoms following storage. Currently, visualization of ZC symptoms in tubers is used by processors to estimate the percentage of ZC-affected tubers in truckloads of potatoes. This approach, however, is time consuming and relies on evaluations of a small sample size. Thus, it is likely to fail in detecting the asymptomatic late infections. Using several potato genotypes infected at different times during the growing season, this study was set to determine if visible and near infrared spectrometry, and infrared thermal imaging, can be used to distinguish ZC-affected tubers, and to predict the severity of ZC symptoms. The subjective symptom score categorization, commonly used in ZC studies, corresponded with the percentage of the symptomatic area in the tubers sliced at the solon attachment end. The percentage of symptomatic area was also correlated with Lso titer. Reflectance effectively distinguished infected and uninfected tubers with high accuracy; the combined wavelengths 468, 582, 680 and 720-nm were the most effective in predicting symptom severity. Near infrared (NIR) and infrared (IR) thermal imaging failed to distinguish tubers based on Lso infection status after storage. The quantitative measure of ZC severity, and the effectiveness of some visual wavelengths in detecting ZC may help to facilitate selection assays for ZC resistance. While in our study infrared imaging did not appear to be effective in distinguishing Lso- affected tubers after storage, additional studies with field harvested tubers are still needed to evaluate the effectiveness of VIS, NIR and IR spectrometry in screening for ZC.     

Mazama: An Early Maturing, Bright Red-Skinned Cultivar For Fresh Market

Mazama, an early maturing red-skinned cultivar for fresh market use, was jointly released in 2000 by the Agricultural Experiment Stations of Oregon, North Dakota, California, Idaho, and Washington. Mazama was tested in irrigated trials in Oregon from 1990 to 2000 and in the Western Regional Trial in 1994, 1995, and 1997. Mazama produces lower total yields than Dark Red Norland and Red LaSoda, but similar marketable yields with a high percentage of small, high-value tubers and significantly fewer culls. In 22 location-years of replicated Oregon and California trials, Mazama produced 40% and 26% higher marketable yields of U.S. #1s under 280 g than Red LaSoda and Dark Red Norland, respectively. In three years of replicated trials in six western states, Mazama produced 115% and 102% of marketable yields of U.S. #1s under 280 g compared with Red LaSoda and Dark Red Norland, respectively. Mazama tubers are smooth skinned and shallow eyed. Mazama’s bright red color does not fade in storage. Mazama is less susceptible to potato virus Y than Dark Red Norland or Red LaSoda.     

The economic impact of investment in the Pacific Northwest potato variety development program

Genetic improvement has been the principle contributor to productivity growth in almost all field crops. The Pacific Northwest (PNW) had the highest rate of potato yield growth combined with the least amount of varietal change in any specialized major field crop-producing region in North America. A coordinated potato variety development program, jointly funded by the USDA, the three land grant universities, and the potato industry in the PNW, was established in 1984. The program developed 17 new potato varieties during the 1989–2001 period, two of them are emerging as successful processing varieties. Ranger Russet, released in 1991, and Umatilla Russet, released in 1998, possess several desired quality and production traits. The most important of these traits is 20% higher processing yield than present varieties. Since their release, there has been significant increase in the percentage of potato area planted with these new varieties. The weighted average adoption rate of these new varieties in the PNW in 2000 was about 16% of the area planted with potato. This represents 32.5% of Washington’s potato acreage, 14.3% of Oregon’s potato acreage, and 9.0% of Idaho’s potato acreage. The benefit to investments in the PNW Potato Variety Development Program attributed only to the flow of benefits from the adoption of Ranger Russet and Umatilla Russet is estimated at over $104.3 million in year 2000 and projected to increase to $213.595 million in year 2014 and thereafter. Rate of return to investment is estimated at 35%.     

Variation in Bactericera cockerelli (Hemiptera: Triozidae) Oviposition,Survival, and Development on Solanum bulbocastanum Germplasm

The potato psyllid, Bactericera cockerelli, is a key pest of potato and important vector of the pathogen that causes zebra chip disease. Control of zebra chip relies entirely on the use of insecticides to reduce populations of this vector. The development of potato varieties resistant to B. cockerelli would contribute to cost-effective control of this insect. Wild potato germplasm are key sources for desirable traits including pest resistance to develop new potato cultivars. Our objective was to screen Solanum bulbocastanum germplasm for resistance to B. cockerelli. The combined use of choice and no-choice assays demonstrated considerable variability among S. bulbocastanum populations in their susceptibility to psyllids. At least six S. bulbocastanum populations exhibited resistance to B. cockerelli: PI 243512, PI 243513, PI 255518, PI 275194, PI 275197, and PI 283096. The documentation of the variability among S. bulbocastanum germplasm populations in their susceptibility to B. cockerelli can aid the development of potato cultivars that are naturally resistant to the potato psyllid.