Glycine tabacina, native to Australia, is an alternate host of Erysiphe diffusa causing powdery mildew on soybean

Abstract

Powdery mildew, caused by Erysiphe diffusa, is an emerging pathogen in Australian soybean crops. Since its initial detection in 2012, the disease has been observed every season in soybean paddocks throughout Australia. It is not known how E. diffusa survives between soybean cropping seasons in the Australian environment. This study identified the native Glycine species, G. tabacina, as an alternate host for E. diffusa in Australia. G. tabacina specimens naturally infected with powdery mildew were collected and the pathogen was identified based on morphological characters and nrDNA ITS and MCM7 sequences. Cross‐inoculation experiments demonstrated that the E. diffusa isolates infecting G. tabacina in the field were pathogenic to soybean. This study is the first to report E. diffusa on G. tabacina in Australia. As a perennial native often found in the vicinity of the annual soybean crops, G. tabacina can easily serve as an alternate host for E. diffusa and could be an example of a host range expansion in this powdery mildew species. Weed control in soybean crops, with special attention to the removal of the native Glycine species, may be an option for powdery mildew management for Australian soybean growers.