QUANTITATIVE AND QUALITATIVE SEASONAL-CHANGES IN THE MICROBIAL COMMUNITY FROM THE PHYLLOSPHERE OF SUGAR-BEET (BETA-VULGARIS)

Bacteria, yeasts and filamentous fungi colonizing immature, mature and senescing primary leaves of field grown Beta vulgaris (sugar beet) we re analysed over a complete growing season. Greatest microbial numbers were detected on senescing primary leaves and these numbers increased over most of the season. The number of colonizers detected on mature leaves was found to be stable over most of the study. Filamentous fung i and yeasts were identified to the genus level and the communities fo und to have greatest diversity during the summer months. There was no consistent pattern of diversity according to leaf type. Two genera of filamentous fungi, Cladosporium and Alternaria and two yeast general, Cryptococcus and Sporobolomyces were the most numerous fungal populati ons isolated. Only 8 filamentous fungi and 3 yeast genera were commonl y isolated on PDA (potato dextrose agar). Bacterial strains (1236) wer e isolated on Tryptic Soy Broth (TSB) agar and identified to species, or in some cases sub-species level, by analysis of their fatty acid me thyl ester (FAME) profiles. Isolated bacteria were grouped into 78 nam ed and 37 unnamed species clusters. Greatest number of bacterial speci es were isolated from young plants and leaves, sampled during the autu mn months. Bacterial community diversity was lowest in mid-summer and winter months. Pseudomonas was the most commonly isolated genus and Er winia herbicola the most common species. P. aureofaciens was the only species isolated from soil that was also isolated from the phyllospher e of B. vulgaris throughout the season.