Wednesday, February 2, 2011

Siderophore Production by Trichoderma

This post is in continuation to Competition and Rhizosphere Competence of Trichoderma: A Magical plant health manager.

Siderophores (Gr. “iron-bearers”) are defined as ‘low molecular weight, virtually ferric specific legends, the biosynthesis of which is carefully regulated by iron and the function of which is to supply iron to the cell’. Iron is generally present in the microbial environment as the ferric ion (Fe (III)), which is virtually insoluble in the presence of O2 and therefore, is not available for microbial growth. Siderophore chelate Fe (III) and microbial membrane receptor proteins specifically recognize and take-up the siderophore-Fe-complex. This results in making iron unavailable to rhizosphere microorganisms, including plant pathogens, which produce less or different siderophores with lower binding coefficients. The result is less pathogen infection and biological control. Siderophores also help in improving antagonistic activities, rhizosphere competence and plant growth.
Trichoderma virens is reported to produce three types of hydroxymate siderophores: a monohydroxamate (cis- and trans-fusarinines), a dipeptide of trans-fusarinine (dimerum acid), and a trimer disdepsipeptide (copragen).

In coming post I shall be discussing more about

Monday, January 17, 2011

Competition and Rhizosphere Competence

This post is in continuation with my previous posts on Mechanisms of Anti-fungal Actions of Trichoderma A Magical Plant Health Manager. Today I shall be discussing about the most accepted mechanism of antifungal action Biological Control Agents (BCAs) i.e. Competition and Rhizosphere Competence

Competition is considered as 'classical' mechanism of biological control. It involves competition between antagonist and plant pathogen for space and nutrients. The idea of the involvement of this mechanism in biocontrol by Trichoderma has gained popularity in recent years.

The omnipresence of Trichoderma in agricultural and natural soils throughout the world proves that it must be an excellent competitor. For example, B. cineria conidia require external nutrients for germination and infection when conidia of Trichoderma sp were applied to leaves, germination of conidia of the pathogen was slowed, an effect attributed in part to competition. The competitive ability of Trichoderma and therefore its biocontrol potential is affected by soil properties.
In coming posts I shall be talking about Siderophore Production by the Trichoderma species. These help in plant growth promotion........

Saturday, January 15, 2011

Antibiosis: Mechanisms of Antifungal Action

This post is a continuing series of the Trichoderma a Magical Plant Health Manager:
This is the second major mechanism implicated in the biocontrol of pathogens by Trichoderma. Trichoderma species are reported to produce a number of antibiotics. These include gliotoxin and glioviridin from T. virens, viridin, alkyl pyrones, isonitriles, polyketides, peptaibols, diketopiperazines, sesquiterpenes and some steroids from other Trichoderma species.
My next post will be on the most accepted mechanism of anti-fungal action of the BCAs i.e. Competition .

Tuesday, January 11, 2011

Mechanisms of Antifungal Action of Trichoderma:Enzymes

Its quite a long time I have posted anything on this blog. There were certain technical reasons for not posting the anything. Now the problems seams to be resolved therefore I shall be continuing on Trichoderma a Magical Plant Health Manager.

Most of the pathogenic fungi contain chitin and Beta-glucans in their cell walls. Dissolution or damage of these structural polymers has adverse effects on the growth of these fungi. Recent research work has implicated a major role of enzymes in biological control by Trichoderma species and the secretion of enzymes is reported to be an integral step of the mycoparasitic process of Trichoderma. Trichoderma species secrete a number of hydrolytic enzymes, which includes chitinases, proteases, cellulases, glucanases and xylanases. Chitinases and beta-1,3 glucanases secreted by T. harzianum plays an important role in degrading hyphae of S. rolfsii. Various enzymes that are present in the different Trichderma species includes protease, beta-1,4-glucanases, exo alpha-1,3- glucanase (AGN 13.1).

Dear Sharad as you have suggested that I shall write on Apple Diseases one by one, surely I shall be writing after finishing off this topic. Hope you will bear with me....