A recent survey of worldwide isolates of Stagonospora nodorum showed that all Australian isolates expressed the host-specific toxin ToxA (Stukenbrock and McDonald 2007). In contrast, very few Chinese isolates did. All the Australian Pyrenophora tritici-repentis isolates that were tested expressed ToxA. We therefore postulated that the wheat gene that confers sensitivity to ToxA, Tsn1, would vary in prevalence in wheat cultivars in use in the two countries. Contrary to expectation, 10 out of 21 Chinese cultivars responded to ToxA as did 26 out of 46 Australian cultivars. The result suggests that ToxA has not had a determining effect on the survival of wheat cultivars in either country. They also suggest that despite the widespread use of Tsn1 markers in Australia, sensitive alleles are still commonplace. The removal of sensitive alleles from breeders’ lines could be readily achieved and could significantly affect the resistance of wheat to both diseases.