Pyrenophora teres f. teres (Ptt) and P. teres f. maculata (Ptm) are foliar fungal pathogens of barley that respectively cause the net and spot forms of net blotch disease. Both pathogens co-exist on crop residue and reproduce sexually, potentially leading to hybridisation between them and the evolution of new virulent pathotypes that could overcome sources of resistance in current commercial barley varieties. To date only few studies have reported Ptt x Ptm hybrids in the field, but reproduction between Ptt and Ptm has been successfully induced under laboratory conditions.
To investigate the incidence of sexual recombination between Ptt x Ptm in the field, susceptible barley varieties were infected with Ptt and Ptm isolates of opposite mating types at each of three sites to facilitate hybridisation. To test for Ptt x Ptm hybrids, 723 single conidia were isolated from infected leaf samples. Sequence-specific PCR markers amplified across DNA of each isolate indicated that none of the isolates were hybrids. Furthermore DArT (Diversity Array Technology) marker analysis indicated that recombination had taken place among Ptt and among Ptm isolates. These findings suggest that sexual hybridisation between Ptt x Ptm is rare and that there is preference for sexual recombination among isolates of the same form. Further investigations are needed to determine the conditions under which hybridisation may occur in the field.