Most plants have harmless bacteria living inside their tissues, known as ‘endophytes’, which can benefit plants by providing nutrients and suppressing diseases. It may one day be possible to enhance crop plants by altering the species of endophytes living within them, but we still know little about the relationship between plants and endophytes. Scientists have developed a new technique to grow wheat plants without any endophytes, allowing them to introduce different bacterial species into them, which will reveal more about this interaction. The researchers hope that the method could give insights enabling the production of cereal plants with increased yields. The work was carried out at Rothamsted Research, which receives strategic funding from the BBSRC, with support from the University of Reading and Novozymes. It was published in May in the journal Scientific Reports.

Bacterial endophytes live in the spaces between the cells of plant tissues. They can enter plants via the roots, and may live inside stems and leaves, moving through the same vessels as water and sugars. Inside wheat grains, the scientists found that the embryo-derived plants had very few, if any, endophytes. By dissecting the grains and allowing embryonic plants to grow in sterile conditions, they created seedlings lacking endophytes. This allowed them to test whether a range of bacteria were able to enter the seedlings and live as endophytes. The team chose 24 bacterial species that had previously been found in the tissue within wheat plants. They found that 23 of them could colonise this tissue, and the introduced bacteria were found in the leaves after they were introduced to the roots. However, other bacterial species tested as controls were unable penetrate the plants.

Dr Rebekah Robinson, who performed the research, said: “The finding that some bacteria were unable to become endophytic, even in the absence of competing bacteria is exciting, and suggests that the host plant operates a gating system to control entry from bacteria that live around the roots. It will be fascinating to discover how this operates”.

Dr Tim Mauchline, scientist in the Microbial Ecology group at Rothamsted Research, said: “The ability to create wheat plants in which we can control the species of bacterial endophytes will be invaluable for research. It allows us to determine the precise role that particular microbes have on plant health in the absence of a background of other competing species”.  

Wheat is one of the three main cereals grown worldwide, so the crop is a major focus of efforts to improve the quality and quantity of grain produced. Modifying the community of endophyte species inside of wheat plants, perhaps by applying a coating to seeds before planting, could help tackle plant diseases, improving yields for farmers and helping to feed more people with limited resources. To use this approach to control diseases in crops, researchers need to better understand the diversity and effects of endophytes, and how they colonise plants.