Pyrenophora teres is the causal agent of net blotches, which are important foliar diseases of barley (Hordeum vulgare) worldwide. Pyrenophora teres has two forms, P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), which causes the net and spot forms respectively based on the symptoms that they induce on barley. The life cycles of both forms are almost identical in which they can undergo both sexual and asexual reproduction. Sexual reproduction contributes to genetic and pathogenic evolution and provides challenges for development of commercial resistant cultivars. It is necessary to understand the genetic and pathogenic diversity of P. teres to effectively breed commercial barley cultivars with resistance. This will improve productivity for barley growers and industry and help reduce reliance on chemical fungicides. The two forms of P. teres consist of different virulence genes. Sexual recombination between two forms of P. teres provides a potential threat to breeding for resistance as it may result in combination of virulences from the two forms. Hybrids have been reported occasionally in the field. This study was conducted to investigate the frequency of Ptt x Ptm hybrid development in the field where both forms of P. teres co-exist. For this purpose, three field trial sites were established for three successive years and Ptt and Ptm of opposite mating types were inoculated to facilitate hybridisation. In addition, samples collected from barley growing regions in Australia during 1976–2015 were analysed. To identify hybrids between the two forms, twelve Ptt and Ptm specific markers were developed using a whole genome comparative approach. These markers provided a more efficient and robust method than previously developed markers for identification of hybrids. No Ptt x Ptm hybrids were identified in the collected samples. This indicates that sexual recombination between the two forms of P. teres was rare, even where conditions were conducive. Further, pre- and postmating barriers which may be responsible ...