From pathogen to endophyte: an endophytic population of Verticillium dahliae evolved from a sympatric pathogenic population.

The fungus Verticillium dahliae causes wilts of several hundred plant species, including potato and mint. Verticillium spp. also colonize sympatric hosts such as mustards and grasses as endophytes. The evolutionary history of and interactions between pathogenic and endophytic of this fungus are unknown. Verticillium dahliae isolates recovered from sympatric potato, mint, mustard and grasses were characterized genotypically with microsatellite markers and phenotypically for pathogenicity. The evolutionary history of pathogenic and endophytic populations was reconstructed and gene flow between populations quantified. Verticillium dahliae was recovered from all hosts. Endophytic populations were genetically and genotypically similar to but marginally differentiated from the potato population, from which they evolved. Bidirectional migration was detected between these populations and endophytic isolates were pathogenic to potato and behaved as endophytes in mustard and barley. Verticillium dahliae colonizes plants as both endophytes and pathogens. A historical host-range expansion together with endophytic and pathogenic capabilities are likely to have enabled infection of and gene flow between asymptomatic and symptomatic host populations despite minor differentiation. The ability of hosts to harbor asymptomatic infections and the stability of asymptomatic infections over time warrants investigation to elucidate the mechanisms involved in the maintenance of endophytism and pathogenesis.

Does Coinoculation with Different Verticillium dahliae Genotypes Affect the Host or Fungus?

Inferences about Verticillium dahliae are often deduced from experiments where hosts are inoculated with one isolate. The assumption that the outcomes from these experiments scale with V. dahliae diversity is untested. The objectives of this research were to test the hypotheses that (i) coinoculation with combinations of isolates affects plant biomass, disease expression, and fungal colonization; and (ii) hosts select for the specific isolates. Potato, mustard, and barley plants were coinoculated with seven combinations of three isolates. Genotypes recovered from infected plants were genotyped with microsatellite markers. Disease expression and fungal colonization but not plant biomass of potato was affected by coinoculation (F = 7.07, P < 0.0001; F = 2.36, P = 0.0427) and depended on the isolates with which plants were inoculated. One genotype was disproportionately selected for by all hosts. Putative heterokaryons were recovered from mustard plants coinoculated with isolates of different vegetative compatibility groups (VCG). These results support the assumption that mixed infections have marginal impacts on plant biomass but challenge the assumption that they do not affect disease expression and fungal colonization. Finally, this research provides evidence that plants select for specific V. dahliae genotypes and isolates from different VCGs can anastomose in planta.

Verticillium isaacii is a Pathogen and Endophyte of Potato and Sunflower in the Columbia Basin of Washington.

The objective of this research was to test the hypothesis that Verticillium isaacii causes diseases of sunflower and potato plants. Two sunflower genotypes and one potato cultivar were inoculated with five V. isaacii isolates and three pathogenic V. dahliae isolates. Biomass, disease expression, and stem colonization were quantified. Overt wilt symptoms were observed on both sunflower genotypes and potato plants inoculated with a subset of the V. isaacii isolates. Biomass of both sunflower genotypes was not affected by V. isaacii infection. Tuber yields either decreased in response to infection by one V. isaacii isolate or were not affected by infection. Stems of sunflower and potato plants were infected by at least four of the five V. isaacii isolates. A new disease of sunflower and potato is documented. Evidence that V. isaacii exhibits different lifestyles including pathogenicity and endophytism is presented. Finally, this research documents variation in fungal lifestyles that can exist in samples from a single field.

Sudden infant death "syndrome"-Insights and future directions from a Utah population database analysis.

"Sudden Infant Death syndrome" (SIDS) represents the commonest category of infant death after the first month of life. As genome scale sequencing greatly facilitates the identification of new candidate disease variants, the challenges of ascribing causation to these variants persists. In order to determine the extent to which SIDS occurs in related individuals and their pedigree structure we undertook an analysis of SIDS using the Utah Population Database, recording, for example, evidence of enrichment for genetic causation following the back-to-sleep recommendations of 1992 and 1994. Our evaluation of the pre- and post back-to-sleep incidence of SIDS in Utah showed a decrease in SIDS incidence on the order of eightfold following back-to-sleep. An odds ratio of 4.2 for SIDS recurrence among sibs was identified from 1968 to 2013 which was similar to the odds ratio of 4.84 for death due to other or unknown cause among sibs of SIDS cases for the same time period. Combining first through thid degree relatives yielded an odds ratio of SIDS recurrence of 9.29 in the post-back-to-sleep (1995-2013) subset of SIDS cases where similar calculations of first-third degree relatives for the entire time period of 1968-2013 showed an odds ratio of 2.95. Expanded multigenertional pedigrees showing enrichment for SIDS were also identified. Based on these findings we hypothesize that post back-to-sleep SIDS, especially recurrences within a family, are potentially enriched for genetic causes due to the impact of safe sleeping guidelines in mitigating environmental risk factors. © 2016 Wiley Periodicals, Inc.

Pathogenicity and Aggressiveness of Three Alternaria spp. on Potato Foliage in the U.S. Northwest.

Alternaria spp. were collected from potato foliage showing symptoms of early blight and brown spot in the Columbia Basin, WA and Bonners Ferry and Rupert, ID between 2009 and 2011. The aggressiveness of three Alternaria spp. on potato was quantified on nonwounded and wounded detached leaves of 'Russet Norkotah' potato; wounded detached leaves of 'Alturas', 'Ranger Russet', 'Russet Burbank', and 'Umatilla Russet'; and whole plants of Russet Norkotah. Mean infection frequencies (MIF) and area under the lesion expansion curve (AULEC) were significantly greater for Alternaria solani (P = 0.0072 and 0.0002, respectively) than for A. arborescens or A. arbusti on nonwounded leaves. Wounding of tissue significantly increased MIF and AULEC for A. arbusti (P = 0.008 and 0.0047, respectively) and AULEC for A. arborescens (P = 0.01) relative to nonwounded tissue. AULEC did not differ significantly among the three Alternaria spp. when inoculated onto wounded foliage of whole plants (P = 0.34); the AULEC of whole plants was positively and significantly correlated with AULEC on detached leaves (P = 0.03). Umatilla Russet was the most susceptible and Russet Burbank was the least susceptible based on MIF and AULEC for all three pathogen species. Results indicate that A. solani was the more aggressive pathogen of potato in the Columbia Basin, because both A. arborescens and A. arbusti require wounds and A. arbusti lesions do not expand significantly in comparison with A. solani or A. arborescens following inoculation.

Identification and Enumeration of Small-Spored Alternaria Species Associated with Potato in the U.S. Northwest.

A number of Alternaria spp. have been isolated from potato worldwide but only Alternaria solani and A. alternata have been described as pathogenic to this host in the United States. These taxa are easily differentiated based on conidial morphology but species delimitation among the small-spored Alternaria spp. associated with potato are much more challenging. Accurate identification methods for small-spored Alternaria spp. are necessary so that a more thorough understanding of Alternaria epidemiology can be obtained. Isolations of Alternaria fungi from lesions on potato leaves collected in the U.S. Northwest were made between 2008 and 2011. Large-spored taxa (putatively A. solani), were isolated less frequently than small-spored taxa (putatively A. alternata sensu lato), except in 2010. Colletotrichum coccodes was isolated from necrotic lesions in 2008 to 2010 but not in 2011. Frequency of isolation ranged from 0.05 (5%) to 0.11 (11%) during the 3 years the fungus was detected. Anonymous genomic region OPA1-3, previously used for Alternaria systematics, allowed for the discrimination of phylogenetic lineages among 210 small-spored isolates. When OPA1-3 was restricted using enzyme ApaI, 65 isolates (31%) displayed a restriction banding pattern consistent with previously characterized morphospecies A. alternata and A. tenuissima and 145 (69%) displayed a restriction banding pattern consistent with the previously characterized morphospecies A. arborescens. Morphological characterization of a subsample of 59 small-spored Alternaria isolates randomly selected with each restriction pattern was compared with phylogenetic lineage. In all, 54 (92%) isolates were consistently assigned to the same group by both methods. Three isolates exhibited conidial morphologies that were inconsistent with any described morphospecies. A small number of isolates were identified as A. arbusti (infectoria group) via sequencing of the glyceraldehyde-3-phosphate-dehydrogenase locus and BLAST searches.

ADAM "sequence" part II: hypothesis and speculation.

Noted for centuries in humans, a relatively hairless mammal [e.g., Hallero, 1766; Hohl, 1828 in Klunker, 2003], the so-called amniotic deformities, adhesions, mutilations (ADAM) sequence remains causally and pathogenetically incognito. In 1930 Streeter stated " apodictically" that no evidence has been found that intra-uterine amputation is due to amniotic bands or adhesions …" and that his 16 cases provided (histological) evidence for a "germinal origin." He concluded that an amniotic cord was "not an adhesion or inflammatory product but … an anomalous developmental structure and present from the outset." In survivors the "traces" of damaged limb-buds "reveal the scars of poor germ-plasm." In 1958, Willis, in dismissing the amniotic origin of the ADAM defects (or "Streeter" or "Simonart" bands) quoted Keith [1940] to the effect that "(a)mniotic adhesions … are always produced by … the fetus ­ as a result of dysplasia in foetal tissues. They are the result, not the cause, of foetal malformations." Streeter [1930] mentions a potential familial case (56-year-old man and his mother), not controlled by photographs or other records and concluded "that the (ADAM) deformity is not easily transmissible," but "due to the constitution of the germ-plasm." Torpin [1968] concluded, as apodictically as Streeter and Willis, that "… proof of amnion rupture without damage to the chorionic sac is no longer "in question." Considering Torpin's decades-long study of the ADAM phenomenon and review of 494 references (missing many) it is surprising that he does not discuss the relationship between the apparent ADAM defects and other, internal anomalies that maybe present in an affected fetus or infant not evidently caused by the amniotic disruptions, adhesions or mutilations, unless his mind was made up. Our review of these internal and other presumed primary malformations in ADAM is ongoing. However, on a preliminary basis, it seems likely to us that: (1) there is an increased prevalence of such primary anomalies in the ADAM condition confirming the view and experience of others, for example Czeizel et al. [1993]; (2) these malformations (e.g., heterotaxy) may arise as early as gastrulation; (3) that, given the ADAM phenomenon is exclusively ascertained as the ADAM phenotype in fetuses and infants, that is, that its cause and ascertainment are completely congruent, then the apparent amniotic defect must also be regarded as a malformation; (4) that in such a case the ADAM phenomenon with associated primary malformation(s) is a form of syndromal pleiotropy due to one cause yet to be elucidated. To that end we recommend archiving DNA from all affected fetuses coming to autopsy and their parents and placentas and surgical tissues of all viable affected infants for ultimate exome or genome sequencing perhaps with special attention to the syncytin genes.

Effect of Powdery Scab Root Galls on Yield of Potato.

Powdery scab of potato, caused by Spongospora subterranea f. sp. subterranea, has increased in incidence since 1981 to become a major concern for potato production in the Columbia Basin of south-central Washington and north-central Oregon. Disease symptoms consist of pustules on the tuber surface and wart-like galls on roots, stolons, and tubers. In the current study, the effect of powdery scab root galls on potato yield was quantified by comparing yields of cultivars susceptible and resistant to root galling grown on soil naturally infested and noninfested with the powdery scab pathogen. Potato tuber yields for the three yield components of yield per plant, number of tubers, and weight of tubers were not negatively affected by powdery scab galls on roots of Umatilla Russet and Shepody, as indicated by yield ratios ≥1.0 in 3 of 4 years, and also by regression analyses in all 3 years. Regression lines with a nonsignificant slope or slopes that significantly increased with gall index also indicated that root galls did not negatively affect yield. Mean tuber weight increased as gall index increased for Umatilla Russet in 2 of 3 years. Consequently, control tactics directed solely at reducing powdery scab galls on roots are not justified economically under conditions encountered in the Columbia Basin of Washington and Oregon states. Effort has been made to develop resistant cultivars and search for soil applied chemicals to reduce root galls.

Effect of Extended Crop Rotations on Incidence of Black Dot, Silver Scurf, and Verticillium Wilt of Potato.

Potato tubers were collected and evaluated for symptoms and signs of black dot, silver scurf, and Verticillium wilt to determine the effect of extended crop rotations on disease incidences in the Columbia Basin. Incidence of tubers with black dot collected from storage significantly decreased as the number of years between potato crops increased from 3 to 5 years and beyond and significantly increased as the number of previous potato crops increased to 16. The highest incidence of black dot (range of 73 to 98%) was from fields rotated out of potatoes for 1 to 3 years. The mean incidence of black dot was 56% for fields out of potatoes for 0 to 4 years and 12% for fields out of potatoes 5 and more years. A low incidence (0 to 9%) of black dot was detected at 15 years out of potatoes. Years out of potato and number of prior potato crops accounted for 71% of the variability associated with the incidence of black dot. Severity of black dot on tuber periderm peels significantly increased as incidence of tuber periderm peels with Colletotrichum coccodes increased. Coefficient of determination was 0.87 for log severity on regressed on black dot incidence. Incidence of silver scurf was highest from fields out of potatoes for 1 year. Incidence of silver scurf infected tubers significantly increased as the number of previous potato crops increased due to short rotations between potato crops. Incidence of tubers with Verticillium dahliae was not related to years between potato crops or number of previous potato crops. The present study confirmed that black dot can be reduced with rotations out of potatoes greater than 5 years.

Accuracy of Rain Forecasts for Use in Scheduling Late Blight Management Tactics in the Columbia Basin of Washington and Oregon.

Accuracy of prediction was analyzed for 17- and 30-day rain forecasts at two locations in the Columbia Basin to determine whether forecasts were sufficiently accurate to be included as a model component to schedule fungicide applications for potato late blight. Accuracy was partitioned into specificity (percentage of forecasted nonrainfall events classified correctly) and sensitivity (percentage of forecasted daily rainfall events classified correctly). An adjusted sensitivity, which included the forecasted rain day plus the next 2 days, was also used to give a wider target than only 1 day for evaluating accuracy of forecasted rain events. For 17-day forecasts, specificity during the seasonal test period was ≥70% from mid-June through September and specificity over the days of the forecast was >70% for the first 8 days at both locations both years. Adjusted sensitivity over days of the forecast was initially >80% and then decreased as forecasts increased from 7 to 17 days for 17-day forecasts at both locations and years. Sensitivity and adjusted sensitivity during the seasonal test period were both positively correlated with the number of rainy days while specificity was negatively correlated. Adjusted sensitivity was considerably higher for May (month with highest incidence of rain) than July (month with lowest incidence of rain) at both locations. For 30-day forecasts, specificity during the test period was >75% in July and August and adjusted sensitivity ranged from 60 to 100% for time periods occurring in May and June during both sample seasons. Specificity was generally above 80% as days of the forecast increased and adjusted sensitivity varied greatly over days of the forecasts, with extremes between 0 and 100% at both locations and years for the 30-day forecasts. Specificity of 17- and 30-day rain forecasts and adjusted sensitivity of 17-day rain forecasts have utility in scheduling late blight fungicides in the Columbia Basin.

Slow-Rusting Resistance in Native Spearmint to Puccinia menthae.

Rust, caused by Puccinia menthae, is often a serious yield-reducing problem on native and Scotch spearmint in south-central Washington State. Rust resistant mint cultivars would reduce a dependence on fungicides for disease management; however, conventional breeding practices are not possible because commercial mint plants are sterile. Mutant Scotch and native spearmint lines induced by irradiation were evaluated for partial resistance to rust. Latent period and number of uredinia per leaf from urediniospore inoculations in the greenhouse and aecial and uredinial development in the field were quantified. Length of latent period, number of uredinia per leaf, incidence of shoots with aecia, and area under the disease progress curve (AUDPC) for uredinia development all varied significantly among lines and standard cultivars. Length of latent period was significantly longer and number of uredinia per leaf was significantly lower for native spearmint line N87-1 than for most of the other mutant lines, native spearmint, and Scotch spearmint. Line N87-1 had the lowest AUDPC values of all lines and standard cultivars for 3 years in the field. However, line N87-1 had a relatively high incidence of shoots with aecia both of two years in the field. Length of latent period was significantly and negatively correlated with AUDPC 2 of 3 years. Mean incidence of shoots with aecia was not correlated with AUDPC or with length of latent period after urediniospore infection. Rust in native spearmint in south-central Washington State could be satisfactorily managed with slow-rusting resistance when coupled with good irrigation water management and sanitation tactics that limit aecia development on early spring mint foliage.

Fungicide Resistance of Two Species of Alternaria from Potato in the Columbia Basin of Washington.

Fungicides are extensively used in the Columbia Basin of Washington in an effort to manage early blight and brown spot on potato caused by Alternaria solani and A. alternata, respectively. Azoxystrobin and boscalid interfere with cellular respiration, and fungicide resistance is expected to occur in fungal populations due to the narrow modes of action dictated by each fungicide. The objective of this research was to assess A. solani and A. alternata populations in the Columbia Basin of Washington for azoxystrobin and boscalid resistance by initially screening isolates at a threshold concentration using mycelial growth and spore germination. Fifty isolates of A. solani and 58 of A. alternata were randomly selected for screening from 671 isolates collected from potato in the Columbia Basin from 2009 to 2011. Screening at a threshold concentration was done to estimate the range of fungicide resistance within the populations of A. solani and A. alternata in the region. Resistance of five isolates that differed in sensitivity to azoxystrobin and boscalid were then assessed for mycelial growth and spore germination at three fungicide concentrations in order to determine where rates were no longer effective. A. solani mycelial growth ratios and percent spore germination on azoxystrobin-amended media did not change from 2010 to 2011. A slight decrease in resistance of mycelial growth to azoxystrobin was exhibited among A. alternata isolates collected between 2010 and 2011. No change in sensitivity to azoxystrobin was observed in mycelial growth ratios among A. alternata isolates collected between 2010 and 2011. Resistance to boscalid by A. solani increased as indicated by a significant increase in mean mycelial growth ratio from 2010 to 2011, whereas A. alternata showed no change. Spore germination of A. solani was less at 100 µg/ml than at 1 or 10 µg/ml azoxystrobin. Spore germination of A. alternata did not differ among 1, 10, or 100 µg/ml azoxystrobin. Spore germination of A. solani and A. alternata did not differ among 0.5, 5, or 50 µg/ml boscalid. Resistance to azoxystrobin and boscalid in A. solani and A. alternata populations was shown to be present in the Columbia Basin and will likely become widespread with continued used of site-specific fungicides.

Verticillium dahliae populations from mint and potato are genetically divergent with predominant haplotypes.

In total, 286 Verticillium dahliae isolates from mint, potato, and other hosts and substrates were characterized for mating type, vegetative compatibility group (VCG), and multilocus microsatellite haplotype to determine population genetic structure among populations infecting mint and potato. Populations from mint and potato fit a clonal reproductive model, with all isolates a single mating type (MAT1-2) and multiple occurrences of the same haplotypes. Haplotype H02 represented 88% of mint isolates and was primarily VCG2B, while haplotype H04 represented 70% of potato isolates and was primarily VCG4A. Haplotypes H02 and H04 typically caused severe disease on mint and potato, respectively, in greenhouse assays regardless of host origin. Principal coordinate analysis and analysis of molecular variance indicated that mint and potato populations were significantly genetically diverged (P = 0.02), and identification of private alleles and estimation of migration rates suggested restricted gene flow. Migration was detected between infected potato plants and seed tubers, infested tare soil, and field soils. Genetic differentiation of V. dahliae from mint and potato may be due to the occurrence of a single mating type and differences in VCG. Populations of V. dahliae in potato and mint were characterized by the presence of aggressive, clonally reproducing haplotypes which are widely distributed in commercial mint and potato production.

Incidence and impact of Verticillium dahliae in soil associated with certified potato seed lots.

Verticillium dahliae causes Verticillium wilt of potato and can be found in soil associated with potato seed tubers. The purpose of this research was to quantify V. dahliae in soil associated with certified seed tubers and determine if this potential inoculum source is related to disease development in the field. Approximately 68% of seed lots assayed contained V. dahliae-infested soil on seed tuber surfaces (seed tuber soil). Over 82% of seed lots contained V. dahliae in loose seed lot soil obtained from bags and trucks used to transport seed tubers. Most samples contained ≤50 CFU/g but some contained >500 CFU/g. Most isolates (93%) were vegetative compatibility group 4A. Populations of V. dahliae in stem sap increased with increasing inoculum densities in field soils only when V. dahliae concentrations in seed tuber soil were low. High concentrations of V. dahliae in seed tuber soil resulted in greater stem sap colonization when V. dahliae inoculum densities in field soil were low (P < 0.01) and resulted in greater pathogen inoculum densities in postharvest field soils (P = 0.04). Seed tubers contaminated with V. dahliae-infested soils may introduce the pathogen into fields not previously cropped to potato or recontaminate those which have received preplant management practices. Long-term management of V. dahliae requires reducing propagules in soil associated with seed lots.

A Plant Stem Inoculation Assay for Assessing Transmission of Phytophthora infestans from Potato Seed Tubers to Emerged Shoots.

A stem inoculation assay was developed to assess transmission of Phytophthora infestans from the base of belowground potato stems to emerged aboveground shoots. Sporangia of P. infestans subsequently developed on aboveground stems after belowground stems were inoculated with isolates BF05 (US 8 genotype), WA10.1 (US 24), and 110B (US 11) by (i) placing a filter paper square saturated with a spore suspension onto nonwounded belowground stem tissue, (ii) placing a filter paper square saturated with a spore suspension onto wounded belowground stem tissue, and (iii) dipping the base of the cut belowground stem into a spore suspension. Plant stems were then incubated in a humidity chamber at 10 to 21.5°C for 7 to 28 days. Incidence of aboveground stems with sporulation was significantly less when stems were inoculated with isolate 110B than with isolates BF05 and WA10.1 but length of latent period did not differ among the three isolates. Incidence of aboveground stems with sporangia was significantly (P < 0.05) greater for 'Russet Norkotah' than for 'Umatilla Russet' when inoculated near the point of seed piece attachment. Incidence of aboveground stems with sporulation did not differ among incubation temperatures of 10, 15, and 21.5°C. Latent period significantly increased as temperature decreased. Age of stem did not appear to affect incidence of transmission. Incidence of transmission of P. infestans to aboveground stems from the base of belowground stems was significantly lowered when aboveground stems were treated with selected fungicides 1 h before inoculation.

Recurrent Large Extrauterine Lipoleiomyoma in a Postmenopausal Woman: A Case Report.

Lipoleiomyoma is a type of tumor usually found in the uterine corpus. The pathophysiology is unclear; however, it is commonly seen in obese perimenopausal and postmenopausal women. While intrauterine lipoleiomyoma may be surveilled, there is less information about the management of extrauterine lipoleiomyoma, especially significantly large tumors.  This is a case involving a 51-year-old female who was incidentally found to have a 23-cm extrauterine lipoleiomyoma emanating from the peritoneum between uterosacral ligaments. She underwent hand-assisted laparoscopic removal of an intra-abdominal tumor, which was found to be an extrauterine lipoleiomyoma. Six months later, she was found to have a recurrent mass on a follow-up computed tomography (CT) of the abdomen and pelvis. She underwent a robotic-assisted total abdominal hysterectomy, bilateral salpingo-oophorectomy, and removal of the recurrent tumor.  While the mass is benign in nature, the mass effect that it may cause prompts a discussion about the best course of management and an investigation into recurrence rates, specifically in similar extrauterine presentations.

Dimerization in the Grb7 protein.

In previous studies, we showed that the tyrosine phosphorylation state of growth factor receptor-bound protein 7 (Grb7) affects its ability to bind to the transcription regulator FHL2 and the cortactin-interacting protein, human HS-1-associated protein-1. Here, we present results describing the importance of dimerization in the Grb7-Src homology 2 (SH2) domain in terms of its structural integrity and the ability to bind phosphorylated tyrosine peptide ligands. A tyrosine phosphorylation-mimic mutant (Y80E-Grb7-SH2) is largely dimerization deficient and binds a tyrosine-phosphorylated peptide representative of the receptor tyrosine kinase (RTK) erbB2 with differing thermodynamic characteristics than the wild-type SH2 domain. Another dimerization-deficient mutant (F99R-Grb7-SH2) binds the phosphorylated erbB2 peptide with similarly changed thermodynamic characteristics. Both Y80E-Grb7-SH2 and F99R-Grb7-SH2 are structured by circular dichroism measurements but show reduced thermal stability relative to the wild type-Grb7-SH2 domain as measured by circular dichroism and nuclear magnetic resonance. It is well known that the dimerization state of RTKs (as binding partners to adaptor proteins such as Grb7) plays an important role in their regulation. Here, we propose the phosphorylation state of Grb7-SH2 domain tyrosine residues could control Grb7 dimerization, and dimerization may be an important regulatory step in Grb7 binding to RTKs such as erbB2. In this manner, additional dimerization-dependent regulation could occur downstream of the membrane-bound kinase in RTK-mediated signaling pathways.

Stability of Slow-Rusting Resistance to Puccinia asparagi and Managing Rust in Asparagus.

The stability of slow-rusting resistance to Puccinia asparagi in several asparagus cultivars was evaluated in two replicated field trials. Rust epidemics were monitored in each trial for 8 years spanning a period of 13 years (1983-1990 and 1987-1995). Inoculum of P. asparagi, an autoecious macrocyclic rust, originated each year as teliospores. In the first trial, the cultivars Jersey Titan, Jersey Centennial, Jersey Giant, Delmonte-361, and UC-157 had consistently lower area under the disease progress curve (AUDPC) values than Wash T2 and WSU-1. Cultivar Mary Washington was intermediate between the two groups of resistant and susceptible cultivars in 6 of 8 years. Jersey Titan consistently ranked number 1 for resistance with the lowest AUDPC values all 8 years. In the second trial, Jersey Giant, Delmonte-361, and UC-157 had consistently lower AUDPC values than Larac, Gynlim, Cito, Largo 17-3, and Franklim in each of 8 years. Jersey Giant, Delmonte-361, and UC-157 always ranked low (1, 2, or 3) for AUDPC. A shift from rust-susceptible to rust-resistant asparagus cultivars began in central Washington around 1996. In 2011, resistant cultivars made up nearly 96% of the asparagus plantings. From 1996 to 2011, rust was not considered a problem in commercial fields with slow-rusting resistant cultivars. Use of durable, slow-rusting cultivars, along with sanitation practices that reduced levels of aecia in nonharvested nurseries and on volunteer asparagus plants and judicious irrigation management, has effectively managed asparagus rust in commercial fields for at least 29 years in south-central Washington.

Roles of Infected Seed Tubers and Soilborne Inoculum on Verticillium Wilt of 'Russet Burbank' Potato.

Verticillium dahliae, causal agent of Verticillium wilt of potato, persists in soil as microsclerotia and can be found in infected tubers used for seed. The effects of naturally infected tubers and soilborne inoculum on Verticillium wilt symptoms were compared in the greenhouse. Infected and noninfected tubers were grown in infested and noninfested potting soil. Chlorosis and necrosis were measured and converted to area under senescence progress curves (AUSPC). Aboveground stems and progeny tubers were assayed for V. dahliae. Plants from infested soils exhibited significantly greater AUSPC than plants from noninfested soil. Plants grown from infected and noninfected tubers had similar AUSPC and interactions between infected tubers and infested soil were not observed. The pathogen was isolated from the vascular system of 94% of plants grown in infested soils and 8% of plants grown from infected tubers in noninfested soil. Plants grown in infested soil contained microsclerotia on 46% of stems while plants grown from infected tubers in noninfested soils exhibited microsclerotia on <1% of stems. Infected progeny tubers were only recovered from plants grown in infested soil. Seed tuber infection did not contribute to premature senescence or potential inoculum production, indicating that management efforts should focus on reducing soilborne inoculum.

Impact of Seed Lot Infection on the Development of Black Dot and Verticillium Wilt of Potato in Washington.

The fungi Colletotrichum coccodes and Verticillium dahliae are two pathogens of potato which are prevalent in potato field soils and seed tubers. The objective of this study was to investigate the influence of seed lot infection by C. coccodes and V. dahliae on disease severity and yield using infested seed lots and fields with and without potato in their recent cropping histories. Greater incidence of C. coccodes in seed led to more root colonization in 2008 (both field types) but not in 2007 and did not influence tuber quantity or yield. Incidence of infection in seed lots by V. dahliae was not related to canopy necrosis, infection of progeny tubers, or yield. However, seed lots exhibited more V. dahliae aboveground vascular colonization, canopy necrosis, infested plant debris, and infected progeny tubers in 5-year potato rotation fields compared with long potato rotation fields. In general, foliar disease symptoms and yield reductions were not related to levels of either pathogen in seed lots. Symptoms of both diseases were more severe and yields were lower in fields with potato in their recent cropping histories, emphasizing the importance of soilborne inoculum in the development of black dot and Verticillium wilt of potato.