In several plant species, lesion-mimic mutants simulate the disease-resistance response in the absence of pathogens. Interestingly, some of these mutants confer broad-spectrum resistance to diverse pathogens. We previously demonstrated that the HLP (hypersensitive-like phenotype) mutant of bread wheat (Triticum aestivum L.) exhibited spontaneous hypersensitive response (HR) in the absence of any pathogen input. However, when HLP plants showing HR phenotype were challenged with leaf-rust

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... a triticina) they were more resistant than plants of the mother-line of comparable developmental stage that did not show spontaneous HR, suggesting that the HLP mutation may confer enhanced resistance to the fungus. In this paper we validate the aforementioned finding in several wheat genetic backgrounds. Twoway crosses were performed among the HLP mutant and eight wheat commercial stocks, and third backcross progenies with and without spontaneous HR were challenged with leaf-rust to investigate the response to the fungus. Backcrosses to cv. Sinvalocho M.A., the motherline, and cv. Purplestraw, highly susceptible to leaf-rust attack, were used as controls. Third backcross progenies of cvs. Sinvalocho M.A., Purplestraw, Buck Guaraní and Pro INTA Imperial bearing spontaneous HR phenotype were more resistant to the fungal pathogen than third backcross progenies that did not carry the HLP mutation. Other four wheat stocks were as healthy as the HLP mutant. As expected, backcross to the mother-line demonstrated that the HLP mutation conferred an additional resistance to the already healthy performance displayed by the mother-line at adult plant stage. The introgression of the HLP mutation conferred heightened leaf-rust resistance and caused no kernel weight reduction on the backcrossed progenies. Taken together, these data validate the direct use of this type of mutations in disease-resistance breeding.