| Objectives for Today's Class | ||
|---|---|---|
| Reference: Agrios Chapter 3 |
Some plants exude onto their surface compounds which inhibit the germination of fungi (Tomato- Cercospora). Other plants (Onion) produce phenolic compounds that protect them from infection. The interest in chemical defense started with red scaled onions and protocatechuic acid. The observation of the red coloration; while it recognized that there was something chemically different between resistant and susceptible plants, lead to a lot of misconceptions which are still extant. As it turns out, the red color is not necessary for resistance. The red color, or tissue darkening sometimes even to purple or black, is the result of oxidation of phenolic compounds involved. Sometimes the oxidized phenols have very little anti-microbial properties. None-the-less color, or lack thereof, has been take as an indication of resistance.
If the parasite needs a particular recognition site and the host does not provide it then perhaps infection will be avoided.
If the host is lacking a specific attachment/receptor site for a toxin then no toxic activity will occur.
phenols, tannins, chitinases, glucanases
Chitinases are receiving a lot of attention as possible resistance factors and a great deal of Biotech. Research is aimed at providing increased chitinase capacity for cells. What in vivo conditions are necessary for chitinase to be effective? Are these conditions being considered by the biotech. pundits?
An Elicitor is any compound of parasitic origin that elicits the production of an anti-parasite compound by the host.
There is no demonstrable evidence that detoxification of host specific toxins occurs.
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Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln
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