CHARACTERIZATION OF PYRENOPHORA ISOLATES ASSOCIATED WITH SPOT AND NET TYPE LESIONS ON BARLEY IN SOUTH-AFRICA

Single-spored isolates of Pyrenophora associated with spot and net type net blotch of barley were compared using total DNA banding patterns, morphological and cultural characteristics, symptomatology and mating studies. Isolates of spot and net type net blotch were found to vary regarding conidium length and cultural growth rate. Mating studies among and between ascospore, spot and net type isolates proved unsuccessful under the conditions studied. Total DNA polymorphisms of the net, spot and ascospore isolates digested with the restriction enzymes HpaII and HaeIII showed that the isolates have similar banding patterns. Random amplified polymorphic DNA (RAPD) showed that the banding patterns of the spot and net type isolates were again similar, but were distinct from outgroups such as P. semeniperda and P. triticirepentis. The homology in DNA banding patterns of local isolates indicated that the difference in conidium length is insufficient to separate them as two species. It is concluded that spot and net type isolates occurring in South Africa belong to P. teres. Therefore, spot type lesions are caused by P. teres f. sp. maculata, and not by P. japonica as reported previously.