Optimizing plant interactions with mycorrhizal fungi to improve forage productivity and stress tolerance

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Arbuscular mycorrhizal fungi (AMF) and important plant symbionts that provide many benefits to plants, including increased access to soil nutrients, drought tolerance, and salinity tolerance. Optimizing plant interactions with AMF has the potential to enhance agricultural sustainability, although agricultural practices reduce plant benefits from AMF. Breeding plants for rapid growth and nutrient uptake selects against dependency on AMF, whereas tillage, fertilizers, and pesticides reduce the abundance of AMF in the soil. For forage crops, AMF may be especially important as forages are often grown on marginal lands that lave low nutrients, poor nutrient retention, and increased salinity. Little work has been done, however, to optimize the benefits of AMF in forages. We will take a two-pronged approach to this issue: 1) selecting forage plants that respond positively to AMF and 2) identifying and culturing AMF that are beneficial to forage crops, especially in saline conditions. To select for AMF responsive genotypes, we will use existing breeding nurseries of two common forage legumes (alfalfa and sainfoin). We will first identify AMF-associated plant traits (e.g. colonization, AMF composition) that are associated with enhanced growth and tolerance of low nutrients and drought. We will then test whether the progeny of these plants exhibit similar traits and AMF benefits. Importantly, these trials include commercial varieties that will be assessed for AMF benefits and can be immediately recommended. To culture beneficial AMF, we will sample soils from both saline and non-saline native grasslands. This follows from our hypothesis that native grasslands will have more diverse AMF and that AMF sampled from saline grasslands will be more salt tolerant. The cultured AMF will then be used to test whether they increase growth and salinity tolerance of three salt-tolerant forage types: a legume (alfalfa), a perennial grass (tall wheatgrass grass), and an annual grass (barley). Combined, this project will determine if we can breed forage crops for AMF benefits and if we can develop AMF inoculums that benefit forage crops.