Investigating hybridisation between the forms of Pyrenophora teres based on Australian barley field experiments and cultural collections

Pyrenophora teres f. teres (Ptt) and P. teres f. maculata (Ptm) cause net and spot form of net blotch of barley (Hordeum vulgare L.), respectively. Both pathogens co-exist in barley fields and each can reproduce sexually, resulting in hybridisation and potential generation of novel virulences that could overcome barley host resistances. In this study, three field experiments were conducted during three successive years to investigate the occurrence of hybridisation. Susceptible barley was sown and inoculated with Ptt and Ptm. Form-specific PCR markers were used to analyse 822 conidia and 223 ascospores sampled from infected leaf tissue and 317 P. teres isolates collected across Australia during 1976–2015. None of the isolates were hybrids. Investigation of ascospores indicated that hybridisation had taken place within the forms, demonstrating preference for recombination within forms. Possible contributions of reproductive barriers have been appraised but further investigation is required to explore the rare hybridisation between the forms.