Fungal endophytes of barley roots

SUMMARYFungal infections of barley have tremendous agricultural significance, and can be detrimental or beneficial. Beneficial root infections often involve endophytic fungi, but endophytic associations do not always confer benefits on their hosts. Endophyte infection can be negative, positive or neutral for the host. Benefits to barley and other plants infected with endophytic root fungi include an increase in seed yield, enhanced resistance to pathogens and improved stress tolerance. Even if an endophyte is never pathogenic, it is not always beneficial. The most important factors that determine the nature of the relationship are the specific combination of partner genotypes and developmental stage, and the ecological and environmental setting. The nutrient status of the plant and the availability of soil nutrients may have little effect on the degree of beneficial endophyte colonization and, unlike mycorrhizae, there is no apparent increase in endophyte-associated phosphorous transfer. There are indications of an association between successful endophyte colonization and high soil pH and clay content. The greatest benefits to the barley plant resulting from the associations seem to be obtained in abiotically stressed environments. Fungal infection may give the plant a greater ability to cope with the stress if the partners are in a balanced relationship. Each new study reveals an increasing diversity of beneficial fungal root endophytes and the full potential of these organisms is still to be determined. Further studies are urgently required to develop specific beneficial root–endophyte associations, or combination of them, that are tailored to individual barley varieties for maximum impact in agriculture.