Race-specific elicitor

HammondKosack, K.E. et al. (1996) Race-specific elicitors of Cladosporium fulvum induce changes in cell morphology and the synthesis of ethylene and salicylic acid in tomato plants carrying the corresponding Cf disease resistance gene. Plant Physiol. 110, 1381-1394... 

The biochemical similarities of leaf and stem rust elicitors, the missing gene specificity of both elicitors, the fact that an equally active elicitor was isolated from germ tube cell walls of oat crown rust (60), together with the described reactions of different non-hosts to the stem rust elicitor led us to speculate that the isolated elicitors may play a role in the induction of general mechanisms of non-host resistance (130). Although they may be involved in the elicitation of race-cultivar specific resistance as well, race-cultivar specificity in the wheat-stem rust system clearly cannot be explained on the basis of the specificity of the isolated elicitors. One possible explanation would be the occurrence of race-cultivar specific suppressors of the resistance reaction (124,131,132). 

Figure 1. Hypothetical scheme of events leading to race-cultivar specific resistance or susceptibility in the rust system. If the substrate specificity of the fungal cell wall degrading enzymes (e.g., pectinases) is suitable for degradation of a specific host cell wall component (e.g., partly esterified pectin), endogenous suppressors will be produced which prevent the elicitor induced lignification response, thus leading to susceptibility.

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