Hello

What I have seen in the trials of my colleagues is that because successive passes are made in the media and no new pathogen is obtained from its normal state (be it plants, field, etc.), this pathogen loses its pathogenicity. In Cenipalma, we work with Phytophthora palmivora, and my colleagues make frequent passes on cocoa fruits and young palm leaves, in such a way that the pathogen does not lose its virulence.

I hope I could have been useful.

Best Regards.

Dr. Anita

In relation to your question, a classic problem is that the loss of the aggressiveness of isolation is due to the repetitive use for the generation of inoculum, as in growing conditions not faced problems acquisition of energy sources fact that may be related to reduction of its machinery to cause disease. Therefore this continually recommended reactivating isolates and retrieve experiments.

Best Regards

Thank you C.E. Aucique Perez and Rodrigo Andrés Avila Diazgranados ·for yours valuable suggestions. when I was working with the strain Fusarium oxysporum f.sp. cubense I also frequently inoculate the pathogen to banana plant-lets to maintain its pathogenicity.  The question was always there in my mind that why an organism a fungi losses its expression of certain virulence genes over time if they did't have their host plants? In what way the host plant confers virulence to pathogen.  

Dear Dr. Anita Kumari

Pls. find the attached files

Page 446 in: P. Vidhyasekaran. 2007. Fungal Pathogenesis in Plants and Crops: Molecular Biology and Host Defense Mechanisms, Second Edition CRC Press,Pp. 536. ISBN 1420021036, 9781420021035

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044101

http://www.sciencedirect.com/science/article/pii/S1087184514001145

http://www.sciencedirect.com/science/article/pii/S0261219499000708

https://www.apsnet.org/publications/phytopathology/backissues/Documents/1988Articles/Phyto78n01_107.pdf

page 505 in: G. Mulè, John A. Bailey, B.M. Cooke, A. Logrieco. 2012. Molecular Diversity and PCR-detection of Toxigenic Fusarium Species and Ochratoxigenic Fungi: Under the aegis of COST Action 835 ‘Agriculturally Important Toxigenic Fungi 1998–2003’, EU project (QLK1-CT-1998-01380) and the ISPP ‘Fusarium Committee’ Springer Science & Business Media,Pp.221. ISBN1402022859, 9781402022852

http://www.annualreviews.org/doi/pdf/10.1146/annurev.py.32.090194.002333

page  193 in : K. R. Khanna. 1990. Biochemical Aspects of Crop Improvement. CRC Press,Pp.472. ISBN 0849354188, 9780849354182

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3730556/

http://www.upm.es/sfs/E.U.I.T.%20Agricola/Departamentos/Produccion%20Vegetal:%20Botanica/Documentos/2013%20The%20effects.pdf

http://link.springer.com/article/10.1007/s11046-006-0023-z

http://www.mycologia.org/content/97/4/901.full

http://www.sciencedirect.com/science/article/pii/S1319562X11000088

http://www.nature.com/articles/srep21367

http://link.springer.com/article/10.1007/s12600-012-0239-z

https://espace.library.uq.edu.au/view/UQ:205309/s40729781_phd_totalthesis.pdf

https://www.ncbi.nlm.nih.gov/pubmed/18211014

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2687792/

http://www.annualreviews.org/doi/abs/10.1146/annurev.py.32.090194.002333?journalCode=phyto

http://www.apsnet.org/EDCENTER/ADVANCED/TOPICS/Pages/BiologicalControl.aspx

Hoping this will be helpful

Regards

Prof. Houda Kawas

Also

Also

Hoping this will be helpful

Dear Anita,

Fungi and other organisms have many genetic mechanisms of adaptation to changing environment and energy sources. It can be random mutation, transposable genetic elements activation, etc., etc.  If you wish to have a stable results of inoculation you have to maintain the culture of fungi in many replications (at least equal to the number of your inoculation experiments) during your project  by such way that does not need repeatable re-cultivation of test isolate  either on nutrient medium or on susceptible host plant.

Regards

Alex

 Therefore, safe long-term preservation methods are required to ensure fungal survival and retention of any valuable characteristics. To minimize the risk of any morphological, physiological, or genetic changes, several different preservation conditions should be used whenever possible to retain pathogenecity.

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Hi Dr. Anita

I agree with Dr.Aucique Perez

Thank you Houda Kawas  madam for providing me great resources, Thanks  Suresh K Malhotra Sir, Barbara Sawicka mam and  Alex Ignatov. Yes, I get some idea about how fungi losses its pathogenicty, how phenotypic plasticity of it contributes to adapting in changed environment.   Random mutation and  transposable elements not only helps in adaptation but are the sources of variations and diversity. 

Heterokaryosis and micro-evolutionary changes also helps in gradual adaptation and loss or gain of pathogenicty in pathogenic fungi. Thank you all for providing me such wonderful asset.  

Dear Dr.Anita

you most welcome

Houda

Thank you Barbara Sawicka  mam

From a genetic point of view, this might be a possibility especially when we are working with a pure culture. Loss of pathogenicity in this case can be attributed to continuous selfing leading to inbreeding depression of factors related to virulence.

For asexual strains, the nature of the environment (the culture media) and the interaction between the genetic and the culture media can negatively affect the virulence of the strain. 

Thanks, Walter Ajambang 

I studied in regard also. Heterokaryosis plays an important role in loss or gain of pathogenicty in phytopathogenic fungi.

 Penicillium commonly occurs wild in the form of heterokaryons enjoying an advantage in growth rate over the homokaryons which can be extracted from them. You can have a look on following publication.

http://rspb.royalsocietypublishing.org/content/140/898/83

Article The Effect of Long-Term Storage on the Physiochemical and Ba...