Characterisation of toxins from Pyrenophora teres in net form net blotch disease

Abstract

Proteinaceous phytotoxins isolated from culture filtrates of Pyrenophora teres f. teres have been characterised for their role in virulence in net form net blotch disease (NFNB) and whether they can be used directly as a selection tool for NFNB-resistant germplasm. Thirty-six isolates were chosen for phytotoxin production based on: the variety from which isolates were collected, when isolates were collected, how virulent they were and their genetic sub-group. Subsets of isolates sharing genetic similarity were determined by genotypic analysis (microsatellite markers) of over 300 isolates. Virulence/aggressiveness of isolates was tested against 12 key varieties (Barque, Buloke, Clipper, Commander, Fleet, Franklin, Keel, Maritime, Schooner, Skiff, SloopSA, Navigator) and compared with symptoms caused by culture filtrates. The types and extent of symptoms induced varied significantly between isolates and on different varieties. Where an isolate infected a large number of varieties, its proteinaceous phytotoxin mixture (from culture filtrates) also caused damage across a large number of varieties suggesting they may be useful in screening for resistant germplasm. Over 70 individual proteins that may act as virulence factors have also been identified and are currently being characterised for their effect on parents of mapping populations.