STUDIES OF SEASONAL-CHANGES IN THE MICROBIAL-POPULATIONS ON THE PHYLLOSPHERE OF SPRING WHEAT AS A PRELUDE TO THE RELEASE OF A GENETICALLY-MODIFIED MICROORGANISM

Populations of bacteria, yeasts and filamentous fungi colonising leaf 3, the flag leaf and the ears of spring wheat were analysed over two c omplete growing seasons in both the glasshouse and field in 1990 and t he field only in 1991. Bacterial isolates were identified by analysis of their fatty acid methyl-ester (FAME) profiles and a total of 37 gen era and 88 species was identified. Of the 15 bacteria most frequently recovered and identified, Curtobacterium flaccumfaciens, Microbacteriu m lacticum, Pantoea agglomerans, Pseudomonas aureofaciens, Pseudomonas fluorescens, Pseudomonas putida and Serratia plymuthica occurred in b oth years in the glasshouse and field but only Pseudomonas aureofacien s occurred at a similar frequency in all three experimental series. Se veral plant pathogenic species were identified. By dilution plating, 1 2 genera of fungi were identified with Aureobasidium, Cladosporium, pi nk and white yeasts being the most common, occurring at 80% or more of the sampling times and sites. Populations of the major groups of micr obes (pink and white yeasts, filamentous fungi and bacteria) generally increased in size with time on all tissues sampled in both glasshouse and field, despite plants growing faster in the glasshouse than the f ield. However, microbial populations were generally significantly larg er on field grown plants than on glasshouse grown ones. The value of u sing FAME profiles to quantify bacterial populations in environmental samples is considered. The significance of the results in relation to monitoring the impact of a future introduction of a genetically modifi ed microorganism (GMM) into the phyllosphere of wheat is discussed.