Resistance systemic acquired

1 Systemic Acquired Resistance. SAR is the induction of a transient long-distance (translocated) defence response to fungal attack that is distinct from the local production of phytoalexins. The transient nature of SAR is important and has likely been selected in the course of evolution as a corollary to the energy demands that are made on the plant by the permanent mobilisation of resistance mechanisms. However, plants challenged by fungi are sensitised to subsequent attack and the speed of their SAR response is increased. 

The phenomenon is well-known20 and correlates with the accumulation of /M,3 glucanases and chitinases, the cell wall degrading enzymes excreted by some fungi. Chemicals that promote SAR are potential 

---

Vallad GE, Goodman RM, Systemic acquired resistance and induced systemic resistance in conventional agriculture, Crop Sci 44 1920—1934, 2004. 

Gozzo, F. (2003). Systemic acquired resistance in crop protection From nature to a chemical approach.. Agric. Food Chem. 51, 4487-4503. 

Local infection of a plant will stimulate the development of natural defense mechanisms often resulting in an immune reaction toward a variety of pathogens. Certain chemicals can also trigger the same biochemical reactions in plants. Among the chemicals found to induce this systemic acquired resistance (SAR) are thieno[2,3-rf [ 1,2,3]-thiadiazoles 195 <1999JPR341>. 

K. Raschdorf, E. Schmid, W. Blum and B. Inverardi, Increase in Salicylic Acid at the Onset of Systemic Acquired Resistance in Cucumber , Science, 1990, 250,1004-1006. 

Systemic acquired resistance relies upon the stimulation of the natural host mechanisms against fungal attack. Only fungi that are sensitive to those chemical antagonists will be controlled. 

Gorlach, J., Volrath, S Knaufbeiter, G. et al. (1996). Benzothiadiazole, a novel class of inducers of systemic acquired resistance, activates gene expression and disease resistance in wheat. Plant Cell 8 629-643. 

Vallad, G.E. and Goodman, R.M. (2004) Systemic acquired resistance and induced... 

Metraux, J.P. (2001) Systemic acquired resistance and salicylic acid current state of knowledge. Eur. J. Plant Pathol., 107,... 

Park, S.-W., Kaimoyo, E., Kumar, D., Mosher, S. and Klessig, D.F. (2007) Methyl salicylate is a critical mobile signal for plant systemic acquired resistance. Science, 318, 113-116. 

Dong, X. Genetic dissection of systemic acquired resistance, Curr. Opin. Plant Biol. 2001, 4, 309-314. 

Smith-Becker et al. [55] have shown that the first measurable effect of the mobile signal for systemic acquired resistance in cucumber inoculated... 

A metabolic engineering approach has now provided direct evidence for the role of salicylic acid in systemic acquired resistance. Transgenic tobacco plants were produced expressing the "nah G" gene from Pseudomonas putida, which encodes a salicylate hydroxylase that converts salicylic acid... 

As indicated above, although less data is available that for herbicides, fungicides also have been implicated in the appearance of variations in phenolic metabolism. Molina et al. [116] have demostrated that the systemic acquired resistance signal transduction pathway, a salicylic acid-dependent plant-defence mechanism, mediates fungicide action in the plant. 

Uknes, S., Winter, A., Delaney, T., Vemooij, B., Morse, A., Friedrich, L., Nye, G., Potter, S., Ward, E., and Ryals, J., 1993, Biological induction of systemic acquired resistance in Arabidopsis, Mol. Plant-Microbe Interact. 6 692-698. 

Ward, E.R., Uknes, S.J., Williams, S.C., Dincher, S.S., Wiederhold, D.L., Alexander, D.C., Ahl-Goy, P., Metraux, J.-P., and Ryals, J.A., 1991, Coordinate gene activity in response to agents that induce systemic acquired resistance, Plant Cell 3 1085-1094. 

Systemic acquired resistance an inducible defence mechanism in plants... 

---