Resistance to septoria nodorum blotch in the Aegilops tauschii accession RL5271 is controlled by a single gene

Septoria nodorum blotch is the most important leaf disease of wheat in West ern Australia. A potentially useful source of resistance has been identifie d in an accession of Aegilops tauschii. To study the genetics of resistance of this source a cross was made between the resistant Ae. tauschii accessi on, RL5271, and a susceptible accession, CPI110889. The resistant parent to ok significantly longer to develop symptoms, developed significantly fewer lesions and expressed significantly lower levels of disease than the suscep tible parent. The F1 mean response for disease severity indicated there was no complete dominance. The F3 families were classified using three approac hes. In the first approach the individual F3 plant response was used to cla ssify the F3 families. In the second approach the F3 family means and stand ard errors were used to classify the F3 families. In the final approach Bes t Linear Unbiased Predictors of disease score and standard error for each F 3 family derived from a REML analysis were used to classify the F3 families . The genotypic ratios generated by each of the approaches suggested that r esistance is controlled by a single gene. The effectiveness of the resistan ce and its simple genetic control in the Ae. tauschii, accession RL5271 may be a useful resistance source for use in a bread wheat breeding program.