ROLE OF CERTAIN MICROORGANISMS IN BIOCONTROL OF LEAF SPOT DISEASE OF SUGAR BEET.

Abstract

The present study was carried out in order to select and increase the antimicrobial activity of some soil microorganisms to be used in the . biological control of leaf spot pathogens of sugar beet Cercospora hetico/a and Alternaria altemata. This was achieved through isolation, screening and optimization of the nutritional and physical requirements for the most active microorganisms.

The study began by isolating and purifing fourty-seven microorganisms including fungi, bacteria and actinomycetes from Egyptian soils collected from fields cultivated with the sugar beet at Kafr El-Sheikh Govemorate.

I Most of these isolates were found to have antagonistic activity

against C. heticola and A. a/ternata. Out ofthe fourty-seven isolates, ninteen isolates have antagonistic activity against A. altemata, and fom1een isolates against C. heticola.

The four most active isolates against C. beticola and A. altemata were identified. The isolate No. 1 was identified as Streptomyces anulatus (syn. S. cavourensis), the isolate No. 3 was identified as Streptomyces cltromofuscus (syn. S. galhus), the isolate No. 21 was identified as Streptomyces a/hadtmcus and The isolate No. 35 was identified as T. viride.