Endophytes

An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; however, most of the endophyte/plant relationships are not well understood. Some endophytes may enhance host growth, nutrient acquisition and may improve the plant's ability to tolerate abiotic stresses, such as drought, and enhance resistance to insects, plant pathogens and herbivores. As often with other organisms associated with plants such as mycorrhizal fungus, endophytes gain carbon from their association with the plant host.

Endophytes may be transmitted either vertically (directly from parent to offspring) or horizontally (among individuals). Vertically transmitted fungal endophytes are typically considered clonal and transmit via fungal hyphae penetrating the embryo within the host’s seeds, while reproduction of the fungi through asexual conidia or sexual spores leads to horizontal transmission, where endophytes may spread between plants in a population or community.

Most endophyte/plant relationships are not well understood.

Endophytes and plants often engage in mutualism, with endophytes primarily aiding in the health and survival of the host plant with issues such as pathogens and disease, water stress, heat stress, nutrient availability and poor soil quality, salinity, and herbivory. Plant-microbe interactions are not strictly mutualistic, with endophytic fungi potentially becoming pathogens or saprotrophs that only become active and reproduce under specific environmental conditions or when their host plants are stressed or begin to senesce.

Endophytes may benefit host plants by preventing pathogenic or parasitic organisms from colonizing them, by extensively colonizing plant tissues and competitively excluding potential pathogens and herbivores..

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