Application of yeasts as biocontrol agents for controlling foliar diseases on sugar beet plants

Survey of foliar diseases on sugar beet plants during 2008-2009 in Kafr El-Sheikh Governorate, Egypt, indicated that sugar beet plants are attacked by some foliar diseases i.e Cercospora leaf spot caused by Cercospora beticola, powdery mildew caused by Erysiphe betae and rust caused by Uromyces betae. Cercospora leaf spot disease was more epidemic followed by powdery mildew, meanwhile rust disease recorded at lowest levels. Five applications by yeasts i.e., Saccharomyces cerevisiae, Pichia albicans, Candida sake and commercial biocontrol agent Rhizo-N (Bacillius subtilis) as well as fungicide (Topsin-M 70%) significantly reduced powdery mildew disease incidence on sugar beet than untreated plants. Topsin M-70% was the best treatment, it completely suppressed powdery mildew followed by S. cerevisiae, C. sake and P. albicans, meanwhile Rhizo-N was the highly effective treatment in this respect. Also, all treatments were significantly reduced Cercospora leaf spot incidence on sugar beet than untreated plants. Topsin M-70% was the best and significant treatment followed by C. sake, S. cerevisiae and P. albicans. Scanning electron microscopy (SEM) showed that S. cerevisiae highly colonized on leaf surface of sugar beet and adhere itself around mycelium of Erysiphe betae. Sucrose in sugar beet roots was recoded as highly percentage on sugar beet treated by P. albicans followed by Rhizo-N and Topsin M-70% treatments. Topsin M-70% was the best and significantly treatment increased of root weight yields followed by S. cerevisiae then P. albicans and C. sake. On the other hand, Rhizo-N treatment was the lowest treatment increased yields of sugar beet.