PURIFICATION AND CHARACTERIZATION OF PEPTIDES FROM RHYNCHOSPORIUM-SECALIS INDUCING NECROSIS IN BARLEY

A new class of toxic compounds has been identified in culture filtrates of the barley pathogen Rhynchosporium secalis race US238.1. Three necrosis-inducing peptides (NIPs) with relative ssmolecular masses of <10 kDa were purified to homogeneity. NIP1 and NIP2 appear to be non-glycosylated, but NIP3 is a glycopeptide, although its toxic activity resides in the peptide moiety. In bioassays, these toxins were host nonspecific since they caused necrosis in primary leaves of both resistant and susceptible near-isogenic cultivars. However, upon fungal infection, NIP3 and a peptide cross-reacting with antisera raised against NIP1, but with a higher relative molecular mass, were detected only in the susceptible cultivar. The appearance of both peptides in vivo correlated with lesion development. Their possible role in pathogenesis is discussed. © 1991.