author(s)
Y Sireesha and R Velazhahan

abstract
Downy mildew, caused by Peronosclerospora sorghi (Weston & Uppal) Shaw, is an economically important disease of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] in India. The symptoms of downy mildew on sorghum and maize are difficult to distinguish from each other using morphologic criteria. Hence cross infectivity assay was conducted to monitor the development of symptoms in maize and sorghum after reciprocal inoculation. When maize seedlings were inoculated with P. sorghi isolates from maize and sorghum, typical symptoms of downy mildew appeared 5 days after inoculation. Sorghum isolate induced more disease (82%) on maize compared to maize isolate (71%). When sorghum seedlings were inoculated with P. sorghi isolate from maize, typical symptoms of downy mildew were produced. In contrast, sorghum seedlings when inoculated with maize isolate did not produce any symptom of the disease indicating pathogenic variability among the isolates of P. sorghi from sorghum and maize.