Variability in Alternaria alternata Infecting Periwinkle (Catharanthus roseus)

Significant morphological, cultural and pathogenic variability was observed among different isolates of Alternaria alternata infecting periwinkle (Catharanthus roseus). ARS Ganganagar, Saduwala and Karanpur isolates showed excellent sporulation. Hanumangarh junction, Jobner and Phulera isolates showed moderate sporulation whereas, Renwal isolate showed poor sporulation with a little colony diameter. Isolates differed in their conidial length and width. Number of horizontal and vertical septa varied between 3 to 8 and 2–5, respectively. All the isolates were pathogenic to periwinkle and produced characteristic symptoms of disease. ARS Ganganagar isolate was found most virulent and produced 80% infection. Minimum infection was observed with Jaipur isolates.