The Phakopsora pachyrhizi-Kennedia rubicunda host-pathogen association and its relation to leaf rust of Glycine spp

Abstract

The relationship of isolates of Phakopsora pachyrhizi found on the coastal legume Kennedia rubicunda to isolates found on Glycine spp. was determined by assessing the virulence of ten Kennedia-derived isolates on a wild line of Glycine canescens and on a commercial cultivar of G. max. These two lines are both known to be susceptible to all Glycine-derived isolates of the pathogen. Three patterns of pathogenicity were detected among the Kennedia-derived isolates with isolates being either avirulent or virulent on both host lines; or being avirulent on G. canescens and virulent on G. max.The pathogenicity of five of these Kennedia isolates of P. pachyrhizi was also tested on ten populations of K. rubicunda. The mean levels of resistance and virulence of the host populations and pathogen isolates respectively showed a considerable range. Significant interactions were detected between particular host population-pathogen isolate combinations. These results were compared with those obtained with two representative isolates of P. pachyrhizi collected on Glycine hosts.