Endophytes in Agriculture: Potential to Improve Yields and Tolerances of Agricultural Crops

Abstract

Endophytic fungi and bacteria live asymptomatically within plant tissues. In recent decades, research on endophytes has revealed that their significant role in promoting plants as endophytes has been shown to enhance nutrient uptake, stress tolerance, and disease resistance in the host plants, resulting in improved crop yields. Evidence shows that endophytes can provide improved tolerances to salinity, moisture, and drought conditions, highlighting the capacity to farm them in marginal land with the use of endophyte-based strategies. Furthermore, endophytes offer a sustainable alternative to traditional agricultural practices, reducing the need for synthetic fertilizers and pesticides, and in turn reducing the risks associated with chemical treatments. In this review, we summarise the current knowledge on endophytes in agriculture, highlighting their potential as a sustainable solution for improving crop productivity and general plant health. This review outlines key nutrient, environmental, and biotic stressors, providing examples of endophytes mitigating the effects of stress. We also discuss the challenges associated with the use of endophytes in agriculture and the need for further research to fully realise their potential.

Keywords: bioprospecting; endophytes; plant health; secondary metabolites; stress tolerance; sustainable agriculture.

Figure 2

Food insecurity illustrations representing the severity of insecurity from 2016 (A) to 2019 (B), outlining the increasing nature of food supply issues, particularly in southern Africa where food supply and undernutrition is increasing at an alarming rate [16].

Figure 1

Visual representation of the effects of an increasing population requiring more housing. Increasing the demand for housing space and township expansion encroaches on farmland, some of which is unable to move relative to this growth. An increased efficiency is required from reduced farmland or crops will have to adapt to survive in these marginal conditions. Endophytes can offer potential solutions for the aforementioned issues.

Figure 3

Overview of range of applications and desirable endophytic impacts upon host plants.

Figure 4

Iron accumulation strategies. (left) Strategy I is conducted by most non-grass plants, whereby iron is taken into the plant’s epidermis through a reduction of ferric iron to ferrous iron (FRO2). This pathway involves H⁺ soil acidification via ATPase AHA2 and phenolic excretion to improve iron availability. (Right) strategy II plants are mainly grasses and can directly uptake ferric iron when complexed with phytosiderophore (DMA) through transporters TOM1 and YS1. This pathway is much more energy efficient and tends to have a higher rate of iron accumulation.

Figure 5

Flowchart outlining the flow on effect that basic nutritional improvements, such as nitrogen, have on downstream processes. Endophyte association can improve a plants ability to metabolise ROS, reducing accumulation and resulting in a greater tolerance to saline conditions.

Figure 6

Sulphur containing amino acids found in plant proteins.