Chemistry: molecular biology and microbiology – Process of mutation – cell fusion – or genetic modification – Introduction of a polynucleotide molecule into or...
Patent
1997-07-25
1999-07-13
Railey, II, Johnny F.
Chemistry: molecular biology and microbiology
Process of mutation, cell fusion, or genetic modification
Introduction of a polynucleotide molecule into or...
435471, 435484, 4352546, 424 932, C12N 115, C12N 1531, C12N 1580, A01N 6304
Patent
active
059226030
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the production of transgenic cells and organisms for controlling phytopathogenic fungi and nematodes and, more particularly, to a method for obtaining strains of Trichoderma spp. that are improved in their capacity as biological control agents for soils.
BACKGROUND TO THE INVENTION
The production of transgenic cells and organisms is opening a very interesting field in genetic engineering; said field is making it possible to incorporate a large number of desirable characteristics into organisms that are directly or indirectly beneficial to man.
At the current state of the art, the methods that are used to control phytopathogenic fungi and nematodes involve the use of large amounts of chemicals, which make it possible to select strains that are resistant to them, making them unsuitable for use in the future, in addition to the fact that they remain in the soil for long periods of time and may prove toxic to both humans and to other species of animals and plants.
Because of this, the ecosystem may be irreversibly affected, which is always undesirable.
One alternative, which people have attempted to apply more widely, is to use agents that exist in nature and are the natural enemies of the phytopathogen(s) to be controlled. Many organisms that can be used in this way have been described in the state of the art. However, the use of said control agents has been limited, primarily because in the majority of the cases the level of control has not been comparable to that achieved with a very efficient chemical fungicide.
Among the most successful agents for biological control of phytopathogenic fungi are those belonging to the genus Trichoderma. These organisms have been favored because they are able to control a wide variety of phytopathogenic fungi that are of great importance to agriculture.
Despite the relative success with which these organisms have been employed, it still has not been possible to achieve the desired levels of disease control.
Various techniques have been used in attempts to obtain organisms of this genus that have improved efficiency as biological control agents; the improvement techniques utilized include that of mutagenesis of both the physical and the chemical types, and protoplast fusion.
Even though the production of strains that have been improved by these techniques has been described, one of the most serious problems that has been encountered is that in these cases some of the organism's desirable characteristics may be affected since it is not possible to direct the changes toward a single type of characteristic, at least as far as is now known in the prior art.
These techniques do not make it possible to modify these organisms selectively, nor do they guarantee that improved strains will be obtained.
A reliable and highly effective way of modifying these organisms without altering characteristics of theirs that are desirable, while still making it possible to do so in a controlled manner, is to introduce the desirable characteristic using the segment of genetic information that codes it in order to transform said organism.
The existing techniques do not make it possible to modify said organisms selectively, nor do they guarantee that improved strains will be obtained.
To date, the literature has given a detailed description of three methods of transforming the genus Trichoderma.
The first of these methods is based on forming protoplasts of this organism and subsequently treating them with polyethylene glycol (PEG) and calcium chloride (CaCl), in combination with thermal shock and in the presence of transformant DNA; this makes it possible to introduce said DNA into the cell being treated. Once inside the cell, the DNA is incorporated into the genome of the microorganism by a mechanism that is inherent in this organism itself (Herrera-Estrella et al., 1990, "High efficiency transformation system for the biocontrol agent Trichoderma spp.", Molecular Microbiology, 4:839-843).
The second method is based on using cells that are treated
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Chet Ilan
Flores-Martinez Alberto
Herrera-Estrella Alfredo H.
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