Microbial Signalling of Rhizobium Bacteria as a Method for Cereal Crop Germination Enhancement

1.Rhizobium nitrogen-fixing bacteria are a well studied microorganism family in the scientific community and its effects have been investigated thoroughly since its initial identification. This study aimed to research further the interactions of this bacteria with members of non-legume plant families, i.e. the poaceae grass species. This multi-year experimental series focuses on the germination stage of these plants, with varying treatments being applied to the seeds pre-germination in order to first test for a quantifiable effect taking place, and later to characterise the mechanism due to which an effect was noted. The identifier used to establish the presence of an effect was the germination rate of the seeds, which was found by examining the testa of each seed for the emergence of a radicle or plumule. Approximately 15,000 samples were tested during this process, the results of which were subsequently statistically analysed at a 95% confidence level. A conclusive increase of 40% (p<0.0001) was noted in the germination of barley seeds when treated with R. leguminosarum. Following tests which confirmed increase enzymatic activity, tests using a different bacterium (A. tumefaciens) and further review of existing literature, it was deemed likely that this effect was due to the release of lipo-chitooligosaccharides (LCOs) by the bacteria. It has been established that synthetically isolated LCOs can positively effect barley germination. It is believed that this is the first time it has been demonstrated that free Rhizobium bacteria in suspension can stimulate faster germination in the poaceae species due to the natural release of LCOs by the bacteria.