Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2003
Publication Date: 11/14/2003
Citation: NAVARRE, D.A., THOMAS, P.E., BROWN, C.R., KACHROO, P. SYSTEMIC ACQUIRED RESISTANCE IN POTATO. ACTA HORTICULTURAE, 619:177-181. 2003. Interpretive Summary: This paper reports on systemic acquired resistance (SAR) in potato, a natural plant defense mechanism in which plants activate certain defenses in response to a pathogen attack. A plant expressing SAR has enhanced protection against a wide range of pathogens that can last for weeks to months. SAR can also be activated by spraying with certain chemicals that activate the plant's defenses and are environmentally friendly. Over ten companies now market products purported to induce SAR. Manipulating a plant's inducible defenses for disease and stress protection is a strategy with tremendous potential, but will likely require optimization for each crop. We are characterizing SAR in potato and have found significant differences in SAR signaling relative to other crops. At least some of the PR genes that are turned off in most plants until activated by for example, pathogen attack, are constitutively on in potato. Salicylic acid is a compound that plays a critical role in regulating certain plant defenses, and is normally present in low levels unless induced by pathogen attack or stress. However, salicylic acid is present in high levels of all potato tissues examined. The consequences of the high constitutive levels of PR proteins and salicylic acid for potato diseases and stress resistance is unknown, but are likely very significant and will be analyzed in future studies.
Technical Abstract: Systemic acquired resistance (SAR) is a defense mechanism that is increasingly being exploited for crop protection. However, successful utilization of SAR will likely require optimization of defense induction for each crop followed by a determination of the pathogens against which SAR is effective. We are examining the capacity of different potato tissues to mount an SAR response. Both free and bound basal salicylic acid concentrations were measured in leaves, flowers, stems, roots and tubers. SA levels were the highest in leaves and flowers, with concentrations of up to 15 mg/gram fresh weight. Relative to Arabidopsis or tobacco, high SA levels were also found in stems, roots and tubers. SAR induction by different SAR elicitors, including harpin and BTH was examined. PR-1 was pressed constitutively, in the absence of elicitation. Little or no increase in PR-1 gene expression was seen after treatment with SAR inducers.