Fitness of Races 0 and 1 of Phytophthora parasitica var. nicotianae

Deployment of tobacco (Nicotiana tabacum) varieties with complete resistance to race 0 of Phytophthora parasitica var. nicotianae has led to a rapid increase in the field populations of race 1 in North Carolina. In a field study, population levels of race 1 decreased relative to race 0 when cultivars with partial resistance to both races were planted, suggesting that race 1 isolates were less fit than race 0 isolates. Experiments were conducted to quantify differences in aggressiveness and survivability of the two races. Tobacco varieties with low, moderate, or high levels of partial resistance were inoculated with 60 pathogen isolates, and symptom development was monitored for 3 weeks. Race 0 isolates were more aggressive than race 1 isolates on cultivars with moderate or high levels of partial resistance; incubation periods were shorter and root rot severity was greater with race 0 isolates. Isolates of race 1, however, caused greater stunting of plants with moderate and high levels of partial resistance than race 0 isolates. Field microplots were infested with either a single race or an equal mixture of each race. Soil samples were collected at the end of two growing seasons and again the following spring. Pathogen populations declined from 40 to 80% during winter months, but population declines for race 0 were lower than for race 1 in each treatment over each winter. Race shifts from race 1 to race 0 that were observed in the presence of cultivars with partial resistance appear to be primarily the result of differences in aggressiveness of the races, with a possible minor effect of enhanced overwintering survival of race 0 compared with race 1.

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Managing the Race Structure of Phytophthora parasitica var. nicotianae with Cultivar Rotation

Plant Disease ◽

10.1094/pd-89-1285 ◽

2005 ◽

Vol 89 (12) ◽

pp. 1285-1294 ◽

Cited By ~ 33

Author(s):

M. J. Sullivan ◽

T. A. Melton ◽

H. D. Shew

Keyword(s):

Partial Resistance ◽

Disease Incidence ◽

Single Gene ◽

Growing Season ◽

Phytophthora Parasitica ◽

Black Shank ◽

Complete Resistance ◽

Race 1 ◽

High Level ◽

Different Levels

Deployment of tobacco cultivars with single-gene, complete resistance to race 0 of the tobacco black shank pathogen, Phytophthora parasitica var. nicotianae, has resulted in a rapid increase in the occurrence of race 1 of the pathogen in North Carolina. Cultivar-rotation studies were conducted in three fields to assess how different levels and types of resistance affected the race structure and population dynamics of the pathogen when deployed in fields initially containing single or mixed races of the pathogen. In a field with both races present, a high level of partial resistance in cv. K 346 was most effective in reducing disease and decreasing the proportion of race 1 in the pathogen population. The deployment of complete resistance in cv. NC 71 resulted in intermediate levels of disease control and race 1 became the predominate race. The cv. K 326, with a low level of partial resistance, had the highest levels of disease, and race 0 was the dominant race recovered. In a field where no race 1 was detected initially, disease incidence was high with the use of partial resistance. Complete resistance was very effective in suppressing disease, but race 1 was recovered after only one growing season. By the end of the third growing season, race 1 was recovered from most treatments where single-gene resistance was deployed. A high level of partial resistance was most effective in suppressing disease in a field where race 1 initially was the predominant race. A rotation between cultivars with single-gene resistance and cultivars with a high level of partial resistance should provide the most effective approach to black shank management. This rotation will reduce disease incidence and minimize race shifts in the pathogen and, over time, should prolong the usefulness of the Ph gene for black shank control in commercial production of tobacco.

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Resistance of Eucalyptus pellita to rust (Puccinia psidii)

Cropp Breeding and Applied Biotechnology ◽

10.1590/1984-70332014v14n4a38 ◽

2014 ◽

Vol 14 (4) ◽

pp. 244-250 ◽

Cited By ~ 9

Author(s):

Marisângela Rodrigues Santos ◽

Lúcio Mauro da Silva Guimarães ◽

Marcos Deon Vilela de Resende ◽

Leonardo Novaes Rosse ◽

Karina Carnielli Zamprogno ◽

...

Keyword(s):

Rust Resistance ◽

Minor Effect ◽

Primary Method ◽

Narrow Sense Heritability ◽

Puccinia Psidii ◽

Eucalyptus Pellita ◽

Eucalypt Plantations ◽

Race 1 ◽

Promising Source ◽

Resistant Genotypes

Eucalypts rust (Puccinia psidii) is currently one of the major diseases in commercial eucalypt plantations in Brazil. The primary method of disease control is the use of resistant genotypes, and, among the different species of Eucalyptus, E. pellita is indicated as a promising source of resistance. In this work, the genetic control of rust resistance in E. pellita through inoculations under controlled conditions of 441 plants from four full-sibling families was studied. Inoculations were performed using the monopostular isolate UFV-2, race 1. All families tested segregated for rust resistance, and the number of resistant plants was higher than susceptible in all crosses. Inheritance models based on few genes did not fully explain the observed segregation patterns, and the narrow-sense heritability of rust resistance was estimated between 32.7% and 37.3%. The results suggested that rust resistance in E. pellita is complex and is controlled by major- and minor-effect genes.

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Species and trichothecene genotype of pathogens causing Fusarium head blight of wheat in Nebraska, USA

Plant Health Progress ◽

10.1094/php-02-21-0020-rs ◽

2021 ◽

Author(s):

Esteban Valverde-Bogantes ◽

Andreia Bianchini ◽

Stephen Wegulo ◽

Heather Hallen-Adams

Keyword(s):

Fusarium Head Blight ◽

Fusarium Species ◽

Management Strategies ◽

Elongation Factor ◽

Head Blight ◽

Single Spore ◽

Additional Species ◽

Growing Seasons ◽

Worldwide Distribution ◽

Pathogen Populations

Fusarium head blight (FHB) is an economically important disease caused by several Fusarium species affecting wheat and other small grain cereals. In recent years, reports of shifts in populations of FHB pathogens around the world have shown that these populations are dynamic and change continuously, often resulting in increased yield losses or changes in the mycotoxins produced in the grain, which highlights the need for increased vigilance. The objective of this research was to identify the species and trichothecene genotypes of FHB pathogens in Nebraska in order to monitor their populations and the major toxigenic risks in the state. A total of 74 single-spore Fusarium isolates were obtained from 42 FHB symptomatic wheat spikes collected from Nebraska fields during the growing seasons in 2015-2018. Most of the isolates were identified as F. graminearum (n=67) based on translation elongation factor 1α (TEF1), trichothecene 3-O-acetyltransferase (TRI101), and reductase (RED) sequences. Additional species included F. boothii (n=3), F. poae (n=2), F. acuminatum (n=1), and one isolate was an F. graminearum × F. boothii interspecific hybrid. All F. graminearum and F. boothii isolates had the 15-ADON trichothecene genotype. This study shows that F. graminearum is not the only pathogen causing FHB in Nebraska and helps expand knowledge on the worldwide distribution of F. boothii. The information obtained from this survey will be useful in developing effective FHB management strategies in Nebraska, since different pathogen populations can cause varying levels of disease intensity and can be selectively sensitive to management tactics.

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Resistance to Phytophthora nicotianae in Tobacco Breeding Lines Derived from Variety Beinhart 1000

Plant Disease ◽

10.1094/pdis-05-12-0480-re ◽

2013 ◽

Vol 97 (2) ◽

pp. 252-258 ◽

Cited By ~ 6

Author(s):

Kestrel McCorkle ◽

Ramsey Lewis ◽

David Shew

Keyword(s):

Partial Resistance ◽

Phytophthora Nicotianae ◽

Sources Of Resistance ◽

Black Shank ◽

Breeding Lines ◽

Stem Resistance ◽

Race 1 ◽

Low Levels ◽

Dh Lines ◽

Rapid Emergence

Black shank, caused by Phytophthora nicotianae, is managed primarily by host resistance. The rapid emergence of race 1 eliminated the usefulness of available complete resistance, leading breeders to search for new sources of resistance. Cigar tobacco ‘Beinhart 1000’ (BH) is highly resistant to all races of P. nicotianae. Doubled-haploid (DH) lines from a cross of BH and the susceptible ‘Hicks’ were evaluated for black shank resistance, and quantitative trait loci (QTL) on linkage groups (LGs) 4 and 8 accounted for >43% of the phenotypic variation in resistance. Forty-three DH lines and parents were evaluated, and genotypes with one or both QTL from BH on LGs 4 and 8 had increased incubation periods and decreased root rot but higher final inoculum levels than genotypes with neither QTL. A low level of stem resistance was observed in BH and DH lines with the QTL from BH on LG 4 but not LG 8. Low levels of leaf resistance were seen for Hicks, BH, and DH lines with both QTL from BH on LG 4 and 8. The partial resistance from BH has not been used commercially and may provide an increase in level of partial resistance in future tobacco varieties.

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Effects of Chemical Control, Cultivar Resistance, and Structure of Cultivar Root System on Black Shank Incidence of Tobacco

Plant Disease ◽

10.1094/pdis-94-5-0613 ◽

2010 ◽

Vol 94 (5) ◽

pp. 613-620 ◽

Cited By ~ 15

Author(s):

Dimitrios F. Antonopoulos ◽

Thomas Melton ◽

Asimina L. Mila

Keyword(s):

Partial Resistance ◽

Adventitious Roots ◽

Early Stage ◽

Laboratory Studies ◽

Critical Factors ◽

Cultivar Resistance ◽

Black Shank ◽

Initial Application ◽

Race 1 ◽

Tobacco Growth

Black shank, caused by the hemibiotrophic oomycete Phytophthora parasitica var. nicotianae, is a major disease of tobacco (Nicotiana tabacum). The rise of race 1 in the late 1990s, after extensive cropping of cultivars possessing the Php gene, confirming immunity to race 0 of P. parasitica var. nicotianae, imposed new challenges to black shank management. The effects of tobacco cultivars and chemical controls with mefenoxam (Ridomil Gold) on black shank incidence were investigated in naturally infested fields. Twenty-five cultivars were tested and the highest resistance for races 0 and 1 of P. parasitica var. nicotianae was provided by RJR 75 and SP 227 based on field and laboratory studies. When race 1 was prevalent, mefenoxam was effective to control black shank. An initial application at an early stage of tobacco growth, such as a few days before or after transplant, was essential to successfully control the disease. In greenhouse experiments, cultivars carrying the Php gene produced fewer and shorter adventitious roots than cultivars possessing only partial resistance to all races of P. parasitica var. nicotianae. Strategies such as use of mefenoxam, especially at an early stage, when adventitious roots are emerging, and planting a cultivar with high partial resistance or possessing the Ph gene when race 1 or race 0, respectively, predominates are critical factors in reducing loss due to P. parasitica var. nicotianae.

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Demography of Bell's Vireos in Missouri Grassland-Shrub Habitats

The Auk ◽

10.1093/auk/117.4.925 ◽

2000 ◽

Vol 117 (4) ◽

pp. 925-935 ◽

Cited By ~ 10

Author(s):

Joel M. Budnik ◽

Mark R. Ryan ◽

Frank R. Thompson III

Keyword(s):

Nest Predation ◽

Molothrus Ater ◽

Nesting Success ◽

Growth Potential ◽

Population Declines ◽

Annual Survival ◽

Rate Of Increase ◽

Study Population ◽

Breeding Seasons ◽

Seasonal Fecundity

Abstract Numbers of Bell's Vireos (Vireo bellii) have declined throughout much of the breeding range in recent years, yet little information exists to determine factors that are causing these declines. We studied Bell's Vireos nesting in grassland-shrub habitats at two study areas in central Missouri to determine reproductive performance, survival, and population growth potential. Birds were color banded and observed during the breeding seasons of 1996, 1997, and 1998 to determine seasonal fecundity. We monitored 124 breeding pairs (127 pair years) and 213 nests. Density declined from 1.00 to 0.80 territories per 10 ha at the first site and increased from 1.11 to 1.33 at the second site during the study. Mean nesting success was 31 ± SE of 0.03% overall and ranged from 13 to 42% among years and study areas; 57% of the pairs fledged at least one young. Low annual production was a function of high rates of nest predation (41% of all nests observed, accounting for 44 to 78% of daily nest mortality annually) and nest parasitism by Brown-headed Cowbirds (Molothrus ater; 29% of nests observed, 17 to 37% of daily nest mortality annually). Mean seasonal fecundity was 1.60 young fledged per pair per year (range 1.00 to 1.79). Annual survival of adults was 61 ± 0.04% and was higher than previously reported. We used our estimates of seasonal fecundity and annual survival of adults to determine the finite rate of increase (λ) for our study population. Our study areas seemingly comprised sink habitats (λ = 0.85). Thus, the vireos on our study areas likely were limited by low reproductive success. Population declines also may be caused by habitat loss, which highlights the need for investigation of historical and current rates of loss of grassland-shrub habitat.

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A Single, Plastic Population of Mycosphaerella pinodes Causes Ascochyta Blight on Winter and Spring Peas (Pisum sativum) in France

Applied and Environmental Microbiology ◽

10.1128/aem.01543-12 ◽

2012 ◽

Vol 78 (23) ◽

pp. 8431-8440 ◽

Cited By ~ 9

Author(s):

Christophe Le May ◽

Michèle Guibert ◽

Aurélie Leclerc ◽

Didier Andrivon ◽

Bernard Tivoli

Keyword(s):

Ascochyta Blight ◽

Plant Diseases ◽

Mycosphaerella Pinodes ◽

Physiological Status ◽

Late Winter ◽

Content Type ◽

Evolutionary Forces ◽

Growing Seasons ◽

Field Peas ◽

Pathogen Populations

ABSTRACTPlant diseases are caused by pathogen populations continuously subjected to evolutionary forces (genetic flow, selection, and recombination). Ascochyta blight, caused byMycosphaerella pinodes, is one of the most damaging necrotrophic pathogens of field peas worldwide. In France, both winter and spring peas are cultivated. Although these crops overlap by about 4 months (March to June), primary Ascochyta blight infections are not synchronous on the two crops. This suggests that the disease could be due to two differentM. pinodespopulations, specialized on either winter or spring pea. To test this hypothesis, 144 pathogen isolates were collected in the field during the winter and spring growing seasons in Rennes (western France), and all the isolates were genotyped using amplified fragment length polymorphism (AFLP) markers. Furthermore, the pathogenicities of 33 isolates randomly chosen within the collection were tested on four pea genotypes (2 winter and 2 spring types) grown under three climatic regimes, simulating winter, late winter, and spring conditions.M. pinodesisolates from winter and spring peas were genetically polymorphic but not differentiated according to the type of cultivars. Isolates from winter pea were more pathogenic than isolates from spring pea on hosts raised under winter conditions, while isolates from spring pea were more pathogenic than those from winter pea on plants raised under spring conditions. These results show that disease developed on winter and spring peas was initiated by a single population ofM. pinodeswhose pathogenicity is a plastic trait modulated by the physiological status of the host plant.

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Role of the Shrub Tamarix nilotica in Dissemination of Fusarium oxysporum f. sp. radicis-lycopersici

Plant Disease ◽

10.1094/pdis.2001.85.7.735 ◽

2001 ◽

Vol 85 (7) ◽

pp. 735-739 ◽

Cited By ~ 6

Author(s):

Y. Rekah ◽

D. Shtienberg ◽

J. Katan

Keyword(s):

Fusarium Oxysporum ◽

Root Rot ◽

Selective Medium ◽

Sampling Location ◽

Susceptible Host ◽

Growing Seasons ◽

Tomato Field ◽

Crown And Root Rot ◽

Pathogen Populations

The saltcedar shrub Tamarix nilotica grows as a weed in the Arava region of Israel. This weed is commonly found in cultivated fields naturally infested with Fusarium oxysporum f. sp. radicis-lycopersici, the causal agent of tomato crown and root rot. Young bushes, 20 to 40 cm tall, were randomly uprooted from different fields. The roots were cut into segments which were placed on Fusarium-selective medium. Although the plants did not show any symptoms of disease, the roots of the shrub were colonized by the pathogen. The incidence of infected saltcedar plants and level of root colonization by F. oxysporum f. sp. radicis-lycopersici decreased with increasing distance of the sampling location from a tomato field infected with crown and root rot. F. oxysporum f. sp. radicis-lycopersici was also isolated from chaff of inflorescence samples taken from mature T. nilotica shrubs. Identity of the pathogen isolates obtained from T. nilotica roots and chaff samples was verified by pathogenicity and vegetative compatibility tests. Roots of T. nilotica plants sown under greenhouse conditions in soil naturally infested with F. oxysporum f. sp. radicis-lycopersici became colonized by the pathogen. Uprooting and removing saltcedar plants throughout the season from fields not cultivated with tomatoes lowered the inoculum density of F. oxysporum f. sp. radicis-lycopersici in the soil from 611 to 6 and from 176 to 10 CFU/g of soil in the 1998-99 and 1999-2000 growing seasons, respectively. These results demonstrate that T. nilotica may contribute to the buildup of the pathogen populations in the absence of a susceptible host. Colonization of saltcedar by F. oxysporum f. sp. radicis-lycopersici is an additional mechanism for survival of this pathogen in the fields and for dissemination through the spread of infested seed or chaff of T. nilotica.

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Metabolite Composition of Paper Birch Buds after Eleven Growing Seasons of Exposure to Elevated CO2 and O3

Forests ◽

10.3390/f11030330 ◽

2020 ◽

Vol 11 (3) ◽

pp. 330

Author(s):

Johanna Riikonen ◽

Minna Kivimäenpää ◽

Vladimir Ossipov ◽

Amelie Saunier ◽

Paula Marquardt

Keyword(s):

Phenolic Compounds ◽

Elevated Co2 ◽

Phenolic Acids ◽

Freezing Tolerance ◽

Polar Compounds ◽

Minor Effect ◽

Target Concentration ◽

Elevated O3 ◽

Growing Seasons ◽

Paper Birch

Research Highlights: Long-term exposure of paper birch to elevated carbon dioxide (CO2) and ozone (O3) modified metabolite content of over-wintering buds, but no evidence of reduced freezing tolerance was found. Background and Objectives: Atmospheric change may affect the metabolite composition of over-wintering buds and, in turn, impact growth onset and stress tolerance of perennial plant species in spring. Materials and Methods: Low molecular weight compounds of paper birch (Betula papyrifera) buds, including lipophilic, polar and phenolic compounds were analyzed, and freezing tolerance (FT) of the buds was determined prior to bud break after 11 growing seasons exposure of saplings to elevated concentrations of CO2 (target concentration 560 µL L−1) and O3 (target concentration 1.5 × ambient) at the Aspen FACE (Free-Air CO2 and O3 Enrichment) facility. Results: The contents of lipophilic and phenolic compounds (but not polar compounds) were affected by elevated CO2 and elevated O3 in an interactive manner. Elevated O3 reduced the content of lipids and increased that of phenolic compounds under ambient CO2 by reallocating carbon from biosynthesis of terpenoids to that of phenolic acids. In comparison, elevated CO2 had only a minor effect on lipophilic and polar compounds, but it increased the content of phenolic compounds under ambient O3 by increasing the content of phenolic acids, while the content of flavonols was reduced. Conclusions: Based on the freezing test and metabolite data, there was no evidence of altered FT in the over-wintering buds. The impacts of the alterations of bud metabolite contents on the growth and defense responses of birches during early growth in spring need to be uncovered in future experiments.

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Climate change and the demographic demise of a hoarding bird living on the edge

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2006.3667 ◽

2006 ◽

Vol 273 (1603) ◽

pp. 2809-2813 ◽

Cited By ~ 45

Author(s):

Thomas A Waite ◽

Dan Strickland

Keyword(s):

Climate Change ◽

Reproductive Success ◽

Cold Storage ◽

Migratory Bird ◽

Lower Latitude ◽

Subalpine Forest ◽

Population Declines ◽

Perisoreus Canadensis ◽

Local Extinctions ◽

Study Population

Population declines along the lower-latitude edge of a species' range may be diagnostic of climate change. We report evidence that climate change has contributed to deteriorating reproductive success in a rapidly declining population of the grey jay ( Perisoreus canadensis ) at the southern edge of its range. This non-migratory bird of boreal and subalpine forest lives on permanent territories, where it hoards enormous amounts of food for winter and then breeds very early, under still-wintry conditions. We hypothesized that warmer autumns have increased the perishability of hoards and compromised subsequent breeding attempts. Our analysis confirmed that warm autumns, especially when followed by cold late winters, have led to delayed breeding and reduced reproductive success. Our findings uniquely show that weather months before the breeding season impact the timing and success of breeding. Warm autumns apparently represent hostile conditions for this species, because it relies on cold storage. Our study population may be especially vulnerable, because it is situated at the southern edge of the range, where the potential for hoard rot is most pronounced. This population's demise may signal a climate-driven range contraction through local extinctions along the trailing edge.

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