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Vegetable IPM Updates Archive
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Plant Disease Resistance (Aug. 8, 2012)

Plants are resistant to many potential pathogens, but what are the mechanisms behind this resistance? One method is physical defense. Just as our skin provides a physical barrier preventing movement of microbes into our bodies, the cuticle or surface covering on plants serves a similar function. Many plant pathogens must adhere to the plant surface for a given time in order to penetrate into the plant and initiate infection and disease. This ability to colonize plants may be disrupted by the amount of wax present and the quality of the cuticle that covers plants. Waxes prevent the formation of a film of water on plants, which is essential for deposition and growth of bacterial and most fungal pathogens on plants. Abundant plant hairs can perform a similar water repellency function. Cuticle thickness and toughness of epidermal cell walls play an important role in the resistance of plants to several pathogens. However, this form of disease resistance can be circumvented by wounds. Many pathogenic bacteria and fungi enter plants only through stomata or other natural openings. The structure and size of these openings can greatly affect the ability of some pathogens to invade plants. These physical plant attributes that are present before exposure to potential plant pathogens play an important role in a plantís ability to resist many disease causing pathogens. Without the presence of these physical barriers, plants in general would be susceptible to many more plant pathogens.

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