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United States Department of Agriculture

Agricultural Research Service

Research Project: PECAN CULTIVATION AND DISEASE MANAGEMENT

Location: Fruit and Nut Research

Title: Induced resistance – does it have potential as a tool in pecan disease management?

Authors
item Bock, Clive
item Wood, Bruce
item Hotchkiss, Michael

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: June 6, 2012
Publication Date: July 1, 2012
Citation: Bock, C.H., Wood, B.W., Hotchkiss, M.W. 2012. Induced resistance – does it have potential as a tool in pecan disease management?. Pecan Grower. 24:20-28.

Interpretive Summary: Pecan scab (Fusicladium effusum) causes losses of pecan nutmeat yield and quality in the southeastern US. New methods are needed to manage the disease. Plants possess resistance mechanisms that can be activated in response to infection with certain diseases (or damage from a pest). These mechanisms are induced by preconditioning a plant or plant part (e.g., a leaf) such that resistance to the disease develops systemically (i.e., translocated to remote locations within the plant) throughout the plant. Depending on the stimulus location and biochemical signaling pathways activated in the plant, this mechanism is called ‘systemically acquired resistance’ (SAR) or ‘induced systemic resistance’ (ISR). It is noteworthy that SAR and ISR mechanisms are subtly different than the type of resistance typically targeted by plant breeders, in which emphasis is usually on identifying and/or selecting for resistance genes. Whereas the ISR mechanisms are activated primarily through the roots (first observed due to plant growth promoting rhizo-bacteria [PGPR]), the SAR mechanisms are activated through exposure of roots or foliage to disease causing agents and subsequent exposure of the plant, or plant part, to particular chemicals. During the last 40 years there has been progress in understanding the SAR/ISR mechanisms in certain crops, with identification of the chemicals and biotic agents that induce them, and application in crop situations to protect plants from disease. The potential for a SAR/ISR-type of response in trees has not been explored as widely as in field crops, and virtually no work has been done to assess whether pecan might possess an inducible, SAR/ISR-type response subsequent to exposure to specific disease or chemical agents.

Technical Abstract: Pecan scab (Fusicladium effusum) causes losses of pecan nutmeat yield and quality in the southeastern US. New methods are needed to manage the disease. Plants possess resistance mechanisms that can be activated in response to infection with certain diseases (or damage from a pest). These mechanisms are induced by preconditioning a plant or plant part (e.g., a leaf) such that resistance to the disease develops systemically (i.e., translocated to remote locations within the plant) throughout the plant. Depending on the stimulus location and biochemical signaling pathways activated in the plant, this mechanism is called ‘systemically acquired resistance’ (SAR) or ‘induced systemic resistance’ (ISR). It is noteworthy that SAR and ISR mechanisms are subtly different than the type of resistance typically targeted by plant breeders, in which emphasis is usually on identifying and/or selecting for resistance genes. Whereas the ISR mechanisms are activated primarily through the roots (first observed due to plant growth promoting rhizo-bacteria [PGPR]), the SAR mechanisms are activated through exposure of roots or foliage to disease causing agents and subsequent exposure of the plant, or plant part, to particular chemicals. During the last 40 years there has been progress in understanding the SAR/ISR mechanisms in certain crops, with identification of the chemicals and biotic agents that induce them, and application in crop situations to protect plants from disease. The potential for a SAR/ISR-type of response in trees has not been explored as widely as in field crops, and virtually no work has been done to assess whether pecan might possess an inducible, SAR/ISR-type response subsequent to exposure to specific disease or chemical agents.

Last Modified: 8/30/2014