Genetic diversity of Phytophthora nicotianae reveals pathogen transmission mode in Japan

Black shank, caused by Phytophthora nicotianae, occurs worldwide and is responsible for significant yield loss in tobacco production in Georgia. Management of the disease has primarily relied on utilization of tobacco cultivars with resistance to race 0 of the pathogen and application of the fungicide mefenoxam. Races of P. nicotianae currently prevalent in tobacco production in Georgia, their sensitivity to mefenoxam, and genetic diversity of the pathogen are largely unknown. To determine population structure and genetic diversity of the pathogen, simple sequence repeat (SSR) markers were used. Three races of P. nicotianae (races 0, 1, and 3) were isolated from infected tobacco plants, with race 3 identified in Georgia for the first time. The majority of isolates were identified as A2 mating type and all isolates were sensitive or intermediately sensitive to mefenoxam at 1 or 10 μg/ml, with effective concentration of mefenoxam for 50% mycelial growth reduction values ranging from <0.01 to 0.12 μg/ml. Bayesian and unweighted pair group method with arithmetic means analyses of 59 isolates using SSR markers grouped the isolates in two major groups. Group I contained 20 isolates, of which 19 isolates were collected from Berrien County. Group II contained 39 isolates collected from Bacon, Cook, Tift, and Toombs Counties as well as one sample from Berrien County. Genetic diversity of the isolates was associated with geographical location of collection, and isolates in group I were primarily (75%) race 1, whereas isolates in group II were primarily (69%) race 0. The presence of a single pathogen mating type at most of the locations implies low probability of sexual recombination that may have contributed to the low genetic diversity at a particular geographical location. Sensitivity of the isolates to mefenoxam indicates that the fungicide remains to be a potent tool for growers to combat the disease. Information generated in the study advances our knowledge about diversity and population structure of P. nicotianae, which facilitates development and implementation of effective disease management programs.

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Evolutionary bi-stability in pathogen transmission mode

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2009.2211 ◽

2010 ◽

Vol 277 (1688) ◽

pp. 1735-1742 ◽

Cited By ~ 23

Author(s):

F. van den Bosch ◽

B. A. Fraaije ◽

F. van den Berg ◽

M. W. Shaw

Keyword(s):

Pathogen Transmission ◽

Transmission Mode

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The context dependent effects of host competence, competition, and the pathogen transmission mode on disease prevalence

The American Naturalist ◽

10.1086/715110 ◽

2021 ◽

Author(s):

Michael H. Cortez ◽

Meghan A. Duffy

Keyword(s):

Disease Prevalence ◽

Pathogen Transmission ◽

Transmission Mode ◽

Host Competence ◽

Context Dependent

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An Assessment of the Genetic Diversity in a Field Population of Phytophthora nicotianae with a Changing Race Structure

Plant Disease ◽

10.1094/pdis-94-4-0455 ◽

2010 ◽

Vol 94 (4) ◽

pp. 455-460 ◽

Cited By ~ 10

Author(s):

M. J. Sullivan ◽

E. J. Parks ◽

M. A. Cubeta ◽

C. A. Gallup ◽

T. A. Melton ◽

...

Keyword(s):

Genetic Diversity ◽

Single Gene ◽

Phytophthora Nicotianae ◽

Bootstrap Support ◽

Resistant Variety ◽

Aflp Analysis ◽

Pathogen Population ◽

Independent Events ◽

Race 1 ◽

High Level

One hundred fifty-three isolates of Phytophthora nicotianae that were collected over a 4-year period from a single field were subjected to amplified fragment length polymorphism (AFLP) analysis to investigate the effect of different types of resistance in tobacco (Nicotiana tabacum) on genetic diversity in the pathogen population. No race 1 isolates were detected in the field prior to initiating the study, but the race was present in multiple plots by the end of the 4-year period. There were 102 race 0 isolates and 51 race 1 isolates characterized. Seventy-six of the 153 isolates had a unique AFLP profile, whereas the remaining 77 isolates were represented by 27 AFLP profiles shared by at least two isolates. Isolates of both races were found in both the unique and shared AFLP profile groups. Twenty-three of the AFLP profiles were detected in multiple years, indicating a clonal component to the pathogen population. Race 1 isolates that were detected over multiple years were always obtained from the same plot. No race 1 profile was found in more than one plot, confirming the hypothesis that the multiple occurrences of the race throughout the field were the result of independent events and not pathogen spread. Three identical race 0 AFLP profiles occurred in noncontiguous plots, and in each case, the plots contained the same partially resistant variety. Cluster analysis provided a high level of bootstrap support for 41 isolates in 19 clusters that grouped primarily by race and rotation treatment. Estimates of genetic diversity ranged from 0.365 to 0.831 and varied depending on tobacco cultivar planted and race. When averaged over all treatments, diversity in race 1 isolates was lower than in race 0 isolates at the end of each season. Deployment of single-gene resistance initially decreased genetic diversity of the population, but the diversity increased each year, indicating the pathogen was adapting to the host genotypes deployed in the field.

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Genetic Diversity and Phylogeny of Antagonistic Bacteria against Phytophthora nicotianae Isolated from Tobacco Rhizosphere

International Journal of Molecular Sciences ◽

10.3390/ijms12053055 ◽

2011 ◽

Vol 12 (5) ◽

pp. 3055-3071 ◽

Cited By ~ 32

Author(s):

Fengli Jin ◽

Yanqin Ding ◽

Wei Ding ◽

M.S. Reddy ◽

W.G. Dilantha Fernando ◽

...

Keyword(s):

Genetic Diversity ◽

Phytophthora Nicotianae ◽

Antagonistic Bacteria

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Observation of surface morphology by reflection electron holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154652 ◽

1989 ◽

Vol 47 ◽

pp. 536-537

Author(s):

N. Osakabe ◽

J. Endo ◽

T. Matsuda ◽

A. Tonomura

Keyword(s):

Phase Shift ◽

Surface Morphology ◽

High Sensitivity ◽

High Energy ◽

Path Difference ◽

Transmission Mode ◽

Electron Holography ◽

Dynamical Process ◽

High Vertical Resolution ◽

Amplification Technique

Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.

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