Over millions of years, plants have formed mutually-beneficial relationships with certain soil microbes. Arbuscular mycorrhizal fungi, for example, help plants to capture nutrients from the soil and protect their hosts from disease, while root-colonising rhizobacteria promote plant growth. While farmers traditionally use chemical pesticides and fertilisers to control plant diseases and improve growth, the EU has recently withdrawn some agrochemicals for safety reasons. To develop alternative treatments, the EU-funded MYCOCROP (Using mycorrhizal-induced resistance as a sustainable alternative to chemical pesticides in cereal agriculture) initiative studied how a mycorrhizal fungus and a ‘plant growth-promoting rhizobacterial strain’ interact to protect wheat from disease.Researchers inoculated two different wheat cultivars either with the mycorrhizal fungus, the rhizobacterium, or both. They then looked at the plants’ weight and chlorophyll content, and evaluated how well the fungus and rhizobacterium colonised the roots of each cultivar. MYCOCROP showed that root colonisation by the mycorrhizal fungus and the rhizobacterium differs between wheat cultivars. Researchers also found that the mycorrhizal fungus increased the number of rhizobacteria on wheat roots. Incredibly, the fungi recruited other rhizobacteria to the roots of plants which had not been inoculated with the selected strain. When both the mycorrhizal fungus and rhizobacterium colonised roots, they acted together to prime the wheat plants’ defence system. This confirmed that in certain wheat cultivars, mycorrhizal fungi can enhance disease defence and improve yields through recruiting plant growth-promoting rhizobacteria to the plant’s roots. Knowing which wheat cultivars are most influenced by mycorrhizal fungi will enable farmers to breed plants that recruit beneficial micro-organisms like rhizobacteria more efficiently. They can also inoculate plants in the field with both microbes as a cheap, environmentally friendly alternative to chemical fertilisers and pesticides.
Soil microbes, mycorrhizal fungi, plant growth-promoting rhizobacteria, wheat, disease defence