Weed hosts ofParatrichodorus allius and tobacco rattle virus in the Pacific Northwest

The ability of several weed species to serve as hosts for tobacco rattle virus (TKV), the causal agent of corky ringspot disease of potato (CRS), and its nematode vector,Paratrichodorus allius, was investigated in greenhouse studies. ViruliferousP. allius multiplied on 24 out of 37 weed species tested, indicating they were suitable hosts of the vector. However, only 11 of these weeds were infected with TRV, as determined by ELISA. The nonhost status of a given weed species was not changed whether the viruliferous vector population originated from CRS problem fields in WA, OR, or ID. Several weeds served as hosts for the vector and virus including kochia, prickly lettuce, henbit, nightshade species (black, hairy, and cutleaf), common chickweed, and annual sowthistle. Virus-freeP. allius acquired TRV from the three nightshade species, volunteer potato grown from TRV-infected tubers, and prickly lettuce, and subsequently transmitted the virus to ‘Samsun NN’ tobacco indicator plants. Thus, some weeds may play a role in the epidemiology of CRS by perpetuating TRV and its vector in a problem field.     

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%.     

Weed and disease incidence in no-till facultative wheat in the Pacific Northwest,USA

Weeds and diseases are major problems in the tillage-based winter wheat (Triticum aestivum)/summer fallow (WW/SF) cropping system of the low precipitation zone (≤300 mm) of the Pacific Northwest. Computer models have estimated that no-till spring crops may reduce soil erosion susceptibility by 95%. However, these annual cropping systems were not economically viable alternatives to the WW/SF rotation. Late-planted WW, also examined as an alternative, was similarly not viable with 35% lower grain yields than WW planted at the normal seeding date for the area. In 2002, two facultative wheat (FW) rotations were incorporated into a long-term, multidisciplinary field study to compare weed and disease incidence with a WW/reduced tillage summer fallow (WW/RSF) system for 4 years. Facultative wheat, not synonymous with late-planted WW, is often derived from SW by WW crosses and exhibits strong photosensitivity and partial sensitivity to vernalization. The two FW systems compared with WW/RSF were no-till FW/no-till spring wheat (FW/SW) and no-till FW/chemical fallow (FW/ChF). Facultative wheat was planted in early-November compared to WW planted in early-September and SW in the following March. Although 16 weed species were present during the study, Bromus tectorum and Salsola tragus were the most pervasive weeds and were found at the highest densities in FW following SW (FW_(SW)). Populations of B. tectorum were often 90% higher in FW_(SW) than in either WW or FW following ChF. The FW/ChF, WW/RSF, and SW following FW had similarly low weed populations when averaged over 4 years. Facultative wheat had less root disease than WW throughout the study. Stripe rust (Puccinia striiformis) was severe in SW in 2005, but did not affect either FW. Based on the low weed and disease incidence coupled with the no-till planting of FW, the FW/ChF system showed promise as an alternative sustainable system to WW/SF.     

Detection and identification of fluorescent compounds in potato tuber tissue with corky patch syndrome

A corky patch syndrome that effects potato tuber tissue may be a later manifestation of pink eye disease of potato although an actual cause and effect relationship between the two diseases has not been firmly established. The causal agent for pink eye of potato is unknown but the disease has been associated with the fungiVerticillium andRhizoctonia and the bacteriumPseudomonas fluorescens. Pink eye and corky patch symptoms on the periderm of affected tubers are accompanied by a band of tissue beneath that is intensely auto-fluorescent when viewed under ultraviolet illumination. Studies to determine the cause of the fluorescent reaction were performed using HPLC and a fluorescence monitor. Three phenylpropanoid compounds, chlorogenic acid, esculin and scopoletin, were found to be involved. It appears that these compounds are produced by tuber tissues in response to pathogen invasion and also as part of the wound healing process. Tissues with corky patch syndrome, silver scurf and root-knot nematode contained high concentrations of chlorogenic acid and esculin and low concentrations of scopoletin. Tissues infected with dry rot were visibly less fluorescent, and contained less chlorogenic acid and esculin, and no detectable level of scopoletin.     

Estimates of sample size for detection and estimation of incidence and severity of corky ringspot of potato

A computer program was developed to simulate the random collection of tuber samples from potato fields with corky ringspot (CRS). Tubers were harvested from 16 plots in the 1993–94 and 1994–95 seasons, and the incidence and severity of CRS symptoms were assessed. Inputs for the program were number of healthy and CRS-affected tubers and severity tuber symptoms from each plot. The output was the mean and the standard error of the mean of disease incidence and severity for 12 different sample sizes. Accuracy and precision for each sample size were estimated to determine sample size. The sample size of 20 tubers was required to detect the presence of CRS in research plots. The binomial distribution was used. With sample sizes greater than 20, the increase in accuracy and precision leveled off regardless of disease incidence and severity values; therefore sample sizes greater than 20 may be unwarranted for evaluation of chemical control tests.     

Soil fumigation and zinc status of soils in relationship to potato speckle-bottom disease development and control

Summary Results from field experiments in Alabama concerning potato speckle-bottom (PSB) disease are reported. These revealed that soil fumigation with D-D ? and zinc deficiency were involved in the correction and induction of PSB symptoms, respectively. Yield and soil test data are presented, and cultural practices are discussed with respect to control or elimination of PSB disease.

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Zusammenfassung Die Blattkrankheit ‘Potato speckle-bottom’ (PSB) wird charakterisiert durch kleine bis grosse nekrotische L?sionen (Abb. 1), die sich zuerst an den untern Bl?ttern entwickeln, gefolgt von Chlorose und eventuelle Blattfall. Es scheint, dass die Krankheit teilweise von einem Zinkmangel herrührt und durch Beifügung von Zinksulphat zu der Düngergabe gemindert werden k?nnte (Tabelle 2). Bodenbegasung mit einer nematiziden Dichloropropen-Dichloropropan-Mischung (D-D ?) verminderte ebenfalls die Symptome (Tabelle 2), und es gab einen Hinweis, dass diese Bodenbehandlung, zus?tzlich zu ihren nematiziden Wirkungen, das verfügbare Zink im Boden vemehrte (Tabelle 4). Die Ertr?ge wurden meistens durch Zinkgaben in den Boden und durch Bodenbegasung erh?ht, dies entweder bei getrennter oder-optimal-bei gemeinsamer Anwendung (Abb. 2, Tabellen 1 und 3), obwohl die Sorte FL 483 eine geringe Verbesserung beim Fehlen der Nematizidbehandlung zeigte. Anbaumethoden wurden in Hinblick auf die Bek?mpfung oder Eliminierung der PSB-Krankheit diskutiert.

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Résumé La maladie du feuillage ‘potato speckle-bottom’ (PSB) est caractérisée par des lésions nécrotiques petites à grandes (fig. 1) qui se développent d'abord à la base du feuillage, et qui sont suivies par un chlorose et une éventuelle abscission. La maladie semble résulter partiellement d'une déficience en zinc et peut être atténuée par l'incorporation de sulfate de zinc dans les engrais appliqués (tableau 2). La fumigation du sol avec le nématodicide ‘melange de dichloropropenedichloropropane’ (D-DR) atténue aussi les sympt?mes (tableau 2) et il y a quelque indication que ce traitement du sol, outre ses effets nématodicides, augmente le zinc disponible dans le sol (tableau 4). L'application au sol de zinc et la fumigation accroissent habituellement les rendements, soit séparément, ou mieux en conjonction (fig. 2, tableaux 1 et 3) toutefois il y aurait peu d'amélioration chez la variété FL 483 en l'absence de traitement nématodicide. Les auteurs discutent des pratiques culturales en fonction de la lutte ou de l'élimination de la maladie PSB.

     

Segregation of total carotenoid in high level potato germplasm and its relationship to beta-carotene hydroxylase polymorphism

High carotenoid potato may have particular value for human health due to the antioxidant properties and the therapeutic value for eye health in patients at risk for macular degeneration. Carotenoid concentrations were determined among the progeny of a cross between two high carotenoid lines derived from diploidPapa Amarilla germplasm from South America. The total carotenoid content ranged from 82 to 2686 µg / 100 g fresh weight (FW). The higher values greatly exceeded the mid-parent value of the cross. An index for yellow tuber flesh color was determined for a subset of the progeny. A cleaved amplified polymorphic sequence (CAPS) assay was developed to distinguish the alleles of beta-carotene hydroxylase (bch) in the two high-carotenoid parents. Abch allele (denoted B) common to the high carotenoid parents co-segregated with yellow flesh in the progeny of a white-flesh x yellow-flesh cross, makingbch an excellent candidate for the classicalY locus, required for yellow tuber flesh. The same allele was also present in all other yellow-fleshed potato clones tested. Genotype atbch explained a portion of the variation of total carotenoid (R²=0.42). Clones homozygous for the B allele (BB) contained, on average, slightly more carotenoid than heterozygous Bb clones, which in turn had much more carotenoid than homozygous bb clones, suggesting a partially dominant gene model. Similarly, bb flesh was significantly less yellow than Bb and BB, the latter two being quite close. Total carotenoid varied considerably between progeny in the Bb and BB genotype categories, suggesting that variation at one or more additional loci have a significant effect on total carotenoid levels. Since the total carotenoid levels in manyPapa Amarilla cultivars and progeny are much higher than those in white- and yellow-fleshed tetraploid cultivars, it may be possible to breed for high carotenoid values in tetraploid germplasm by introducing one or more genes derived fromPapa Amarilla germplasm.     

Electrolyte leakage of aging potato tubers and its relationship with sprouting capacity

Summary With advancing physiological age of potato tubers an increase in electrolyte leakage from tuber tissue was observed for various seed lots. This increase was most marked after tubers exhibited sprout growth and corresponded with a decline in tuber water content. Leakage increased minimally with storage time when sprouting was prevented or limited by either dormancy, low storage temperature, or frequent desprouting. Sprouting capacity of tubers increased to a maximum and then declined with storage time. This decline coincided with the increase in electrolyte leakage, suggesting that membrane integrity was one determinant in vigour of seed potato tubers. The pattern of electrolytes leaking from tuber tissue could be described by a function composed of a saturable and a linear component, suggesting two different sources contributing to the leakage. The saturable component, expected to reflect membrane integrity, was most responsive to aging treatments. H/LA Paper No. 93-13. Department of Horticulture and Landscape Architecture, Project No. 1984. College of Agriculture and Home Economics Research Center, Washington State University. This work was supported in part by grant funding from the Washington State Potato Commission.     

Salmon-derived nitrogen in terrestrial invertebrates from coniferous forests of the Pacific Northwest

Background  

Bi-directional flow of nutrients between marine and terrestrial ecosystems can provide essential resources that structure communities in transitional habitats. On the Pacific coast of North America, anadromous salmon (Oncorhynchus spp.) constitute a dominant nutrient subsidy to aquatic habitats and riparian vegetation, although the contribution to terrestrial habitats is not well established. We use a dual isotope approach of δ¹⁵N and δ¹³C to test for the contribution of salmon nutrients to multiple trophic levels of litter-based terrestrial invertebrates below and above waterfalls that act as a barrier to salmon migration on two watersheds in coastal British Columbia.     

Potato early dying disease in the Pacific Northwest caused byErwinia carotovora pv.carotovora andE. carotovora pv.atroseptica

Premature death of potato vines is widespread in irrigated potato fields of the Pacific Northwest.Verticillium dahliae is a major cause of early dying in fields with a history of potato production, but in fields new to potato production, or those that have been fumigated and have a lowV. dahliae population in the soil, premature death of vines can also occur.Erwinia carotovora pv.carotovora (Ecc) andE. carotovora pv.atroseptica (Eca) have been implicated in the early dying disease syndrome in these fields. Both bacterial pathogens are associated with symptoms similar to those caused byV. dahliae; i.e., a progressive chlorosis and necrosis of the foliage and vascular discoloration that may extend a short distance up the stem. Greenhouse pathogenicity studies on cv. Russet Burbank cuttings in which symptom development was identical to that produced byV. dahliae have verified thatEcc andEca can cause potato early dying.     

Differences in free and protein-bound tyrosine among potato genotypes and the relationship to internal blackspot resistance

Twelve potato clones were selected to represent the full range of internal blackspot response in order to determine the relationships between tuber protein, free tyrosine, and blackspot susceptibility. The blackspot reaction for each clone was consistent over five growing seasons, including tubers grown over a normal season (mature), and short season (immature) during one year. The blackspot index, determined by either an abrasive peel test or an impact bruise test, was highly correlated with the tyrosine content of the tubers (r = 0.90 p = 0.001 for the means of each clone over five location-years). Tubers with free tyrosine levels below 4 μmole/g dry weight consistently showed a resistant blackspot response. The relationship between tyrosine and blackspot susceptibility was also found in stolon and bud ends from five of the clones which represented the extremes of blackspot reaction and genetic diversity. Bud end samples of each of the clones had lower tyrosine content and a corresponding reduction in blackspot compared with stolon ends. Phenols, other than tyrosine, showed no consistent relationship to the blackspot reaction. There was a very high negative correlation between free tyrosine and estimated protein-bound tyrosine. R values ranged from ?0.85 to ?0.97 (p = 0.001) for mature tubers of the 12 clones over 4 growing seasons. Total tyrosine (free, plus protein-bound) remained relatively constant. There were no significant differences in mean total tyrosine content among the 12 clones over five location-years of testing; and there were no significant differences among the five growing seasons except for the short season (immature) tubers which were 14% lower in total tyrosine content. These results indicate a remarkably constant level of total tyrosine production in the twelve clones studied, that represented diverse genetic backgrounds. Mature tubers of all genotypes contained 26 ± 1 μmole/g dry weight total tyrosine. Partitioning of tyrosine between tuber protein and the free amino acid pool varied with genotype and appeared to be a major determinate of blackspot resistance.     

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.