Evaluation of certain Penicillium frequentans isolates against cercospora leaf spot disease of sugar beet

Abstract

The impact of six local isolates of Penicillium frequentans recovered from healthy sugar beet (Beta vulgaris L.) leaves was evaluated against Cercospora beticola, the causal pathogen of Cercospora sugar beet leaf spot under laboratory and field conditions. In in vitro studies, all the six isolates were able to inhibit the mycelial growth of C. beticola with variation in their antagonistic capability. P. frequentans isolates produce pectinase and cellulase at different degrees. There was a correlation between enzyme activity and the antagonistic ability for each isolate. The high antagonistic ability isolates had the most enzyme activity. In field studies, some adhesives such as agar, starch flour, white glue, gum, and commercial adhesive (Triton Mok) were added to conidia spore suspensions of P. frequentans at 1% to improve conidial adhesion to sugar beet plant surface. Data also showed that all adhesives increased (P = 0.05) the efficiency of the spore suspension of P. frequentans to control the disease. The starch flour at 1% gave a significant reduction in disease severity from 43.23 to 10.42% pre-infection and from 43.23 to 10.52% post-infection. The application of P. frequentans led to improved root yield and the sugar percent of sugar beet crop in two tested seasons.