Quantitative and Qualitative Studies of Phylloplane Bacteria from Lolium perenne

SUMMARY: Populations of heterotrophic bacteria occurring on healthy green leaves of Lolium perenne were estimated using a dilution technique. Bacterial populations in spring and summer were relatively low compared with counts obtained in September when the highest maximum and monthly mean air temperature was recorded. The area of leaf surface colonized rose from about 0·0001 % in May to approximately 0·1 % in September. Over 600 isolates were examined and most found to be Gram-negative and chromogenic. The bacterial populations consisted of only a few taxa and the variations in total numbers were due to changes in the relative abundance of these. The predominant flora were identified to the genera Chromobacterium, Corynebacterium, Pseudomonas and Xanthomonas. Leaf impression and overpour techniques gave some indication of the micro-ecology of bacteria on the leaf, and showed the presence of actinomycetes which were rarely observed on dilution plates.