Re: Contamination

[Maria Delgado <mdlgd@CLEMSON.EDU>]

Jumana;
If your cultures have a plant pathogenic bacteria, (esp. one that banana is
susceptible to) it will most likely attack the tissue first, and there
should be visible signs or symptoms of disease on it while in culture.
Contaminants in the culture media, however, are depending on the media's
sugar or nutrients. I think  the latter is the one  Mr. Herman is referring
to in that paper.
Best Regards,

Maria Delgado

----- Original Message -----
From: jumana serhan <jumana_fuad@YAHOO.COM>
To: <PLANT-TC@TC.UMN.EDU>
Sent: Sunday, February 11, 2001 4:51 PM
Subject: Re: Contamination

> hello,
>   i'd like to share with my experment in banana
> culturing, we had tow sources for banana meristems for
> initiation ( Grand Naine ) , the first one were young
> plantlets that were not planted in the field yet , and
> the other was larger and older and were planted in the
> field .
>  at the initiation ,the first one gave a very low
> contamination % and a great growth rate.
>  the second were worse, with a high contamination% and
> weak growth rate .
>  at the multiplication stage, the first one were good
> in growth with a low contamination % till the third
> multiplicaion , the contamination % exceeded 50% !!
>  while the second one kept on the very low
> contamination % , although that we multiplied them in
> the same day with same techniques , and even we had a
> high contamination % in the cultures that we
> multiplied after the first one which were from another
> generation.
>   the problem is when you know that the first one were
> produced by tissue culture , while the second were
> not!!!!!
>   so if these invisibly contaminated culture we
> produce are holding a pathogenic bacteria , then we
> are helping in spreading a new pathogen in our farming
> land!!!!!
>
>   any comments are welcomed
>   best regards
>   Jumana Serhan
> --- Agricell@AOL.COM wrote:
> > Latent microbial contamination of plant tissue
> > cultures has been described
> > since 1992, particularly by C. Leifert at the
> > University of Aberdeen. The
> > problem is that plant tissue culture medium is not a
> > particulary good growth
> > medium for many microorganisms. They can persist for
> > years without clouding
> > the medium or producing symptoms. The commonly used
> > method for determining
> > whether cultures are "clean" - holding them up to
> > the light to look for
> > cloudiness - is worthless, if the aim is to achieve
> > an axenic culture. All
> > "eyeballing"does is tell you that whatever
> > contaminants are present do not
> > produce visible growth in the medium that you are
> > using, with the explant
> > that you are growing, under the culture conditions
> > that you are using. I
> > wince whenever I read a paper that claims to deal
> > with an axenic or clean
> > culture when the author has used nothing but an
> > "eyeball" test for
> > contamination.
> >
> > The following are two recent Agricell Report
> > articles on latent contamination
> > that may be of interest in the contamination
> > discussion:
> >
> > Ed Herman, Editor
> > Agricell Report
> >
> > New Method for Detecting Latent Contaminants in
> > Plant Tissues
> >
> > (SEPT 98, Agricell Report) It is now well
> > established that microorganisms can
> > survive in plant tissue cultures for many years,
> > through multiple
> > subcultures, with no visible indication of
> > contamination. Such latent
> > contaminants are often difficult or impossible to
> > detect and isolate by means
> > of standard bacteriological methods, but may be
> > harmful to plants in vitro
> > and to plants regenerated from such contaminated
> > cultures. What is even more
> > dangerous is that latent plant pathogens may be
> > inadvertantly spread by
> > micropropagated plants contaminated with latent
> > pathogens.
> >     At the ISHS Conference: Methods and Markers for
> > Quality Assurance in
> > Micropropagation, held 24-27 August 1999 in Cork,
> > Ireland, University of
> > London scientists G. Tsoktouridis, G. Tasiamis and
> > S. Mantel described a
> > PCR-based strategy and protocols that permit rapid
> > detection and isolation of
> > low numbers of latent bacteria in tissue
> > culture-derived plants of Bilbergia.
> > The technique involves amplifying a fragment of the
> > 16S rDNA fragment of
> > bacteria without amplifying the pure plant DNA. This
> > PCR product can be used
> > to classify bacteria by cloning and sequencing.
> >     According to the authors, Use of any
> > combinations of primers and
> > subsequent sequence analysis of any amplified
> > fragment allows the rapid
> > detection and molecular identification of bacteria
> > associated with plants.
> > One combination of primers may detect eucaryotic
> > bacteria . . . present as
> > contaminants . . . and other combinations of primers
> > would even have the
> > potential to allow rapid detection of unculturable
> > bacteria.
> >     Tsoktouridis et al. suggest that their
> > â?omolecular diagnostic toolâ?� can
> > yield more reliable and consistent information about
> > latent contaminants than
> > has hitherto been possible. They add that the
> > potential benefits of the
> > technique offer â?oan extremely attractive
> > opportunity in those cases where
> > high numbers of samples require rapid analysis and
> > appropriate economies of
> > scale.â?�
> >
> > For further information:
> > G. Tsoktouridis, Dept. of Agric. & Hortic., Wye
> > Coll., Univ. of London, Wye,
> > Ashford, Kent TN25 5AH, U.K.
> >
> > Persistence of Pathogens in Plant Tissue Cultures
> >
> > OCT 99, Agricell Report) Because autotrophic plant
> > tissue culture does not
> > require the presence of added sugar, it is believed
> > to be less vulnerable to
> > microbial contamination than heterotrophic culture.
> > At the National
> > University of Ireland, however, S.M. Rafferty and
> > associates have found that
> > human food poisoning pathogens can persist in
> > autotrophic plant tissue
> > cultures despite normal disinfestation procedures
> > and can also persist in
> > regenerated plants. Rafferty et al. inoculated
> > cabbage seedlings with E.
> > coli, S. marcescens and enterococci. The seedlings
> > were disinfested by
> > placing them in 80% ethanol for 45 seconds, 2%
> > stericol for 30 minutes, then
> > washed in sterile distilled water three times. After
> > disinfestation, some of
> > the plantlets were homogenized and the homogenate
> > was plated onto an
> > appropriate bacterial culture medium and incubated.
> >     The authors reported at the meeting that
> > bacterial isolates could be
> > recovered both from direct culture of seedlings and
> > from homogenates. The
> > bacteria persisted during autotrophic culture,
> > apparently using plant
> > exudates as a carbon source, and could be repeatedly
> > re-isolated through
> > serial subcultures. Although some plants were
> > asymptomatic, in others the
> > bacteria became vitropathic (pathogenic in vitro).
> > When seedlings from these
> > cultures were transferred to greenhouse or field
> > conditions, bacteria could
> > be isolated endophytically initially and
> > epiphytically for long periods of
> > time, both from the plants and from the substrates
> > upon which they were grown.
> >     It thus appears that, despite normal
> > disinfestation procedures, in vitro
> > culture has the potential of spreading pathogenic
> > microorganisms, even when
> > the culture is performed under autotrophic
> conditions.

---

[Subject Prev][Subject Next][Thread Prev][Thread Next]

---

Plant-tc Listserv Homepage | 
Subject Index | 
Thread Index