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Many of the world's soils are experiencing degradation at an alarming rate. Climate change and some agricultural management practices, such as tillage and excessive use of chemicals, have all contributed to the degradation of soil fertility. Arbuscular Mycorrhizal Fungi (AMFs) contribute to the improvement of soil fertility. Here, a short review focusing on the role of AMF in improving soil fertility is presented. The aim of this review was to explore the role of AMF in improving the chemical, physical, and biological properties of the soil. We highlight some beneficial effects of AMF on soil carbon sequestration, nutrient contents, microbial activities, and soil structure. AMF has a positive impact on the soil by producing organic acids and glomalin, which protect from soil erosion, chelate heavy metals, improve carbon sequestration, and stabilize soil macro-aggregation. AMF also recruits bacteria that produce alkaline phosphatase, a mineralization soil enzyme associated with organic phosphorus availability. Moreover, AMFs influence the composition, diversity, and activity of microbial communities in the soil through mechanisms of antagonism or cooperation. All of these AMF activities contribute to improve soil fertility. Knowledge gaps are identified and discussed in the context of future research in this review. This will help us better understand AMF, stimulate further research, and help in sustaining the soil fertility.

Drought stress strongly affects soil biota and impairs crop production, which under climate change will be exacerbated in semi-arid cropping regions such as the Sahel. Hence soil management systems are needed that can buffer against drought. In West Africa, field studies have found intercropping of millet with the native shrub Piliostigma reticulatum improves soil-plant-water relations, microbial activity and diversity, and suppress parasitic nematodes, which can significantly increase crop yield. However, little information is available on its beneficial or negative effects on soils or crops during water stress. Therefore, the objective was to investigate the impact of P. reticulatum in moderating water stress effects on soil properties and pearl millet (Pennisetum glaucum [L.] R. Br.) productivity. In the greenhouse, soil chemical and microbial properties and millet growth were investigated with a factorial experiment of varying levels of soil moisture (favorable, moderately stressed, or severely stressed water conditions) that was imposed for 55 days on soils containing sole P. reticulatum or millet, or millet + P. reticulatum. The results showed that the presence of P. reticulatum did not buffer soils against water stress in relation to soil chemical and microbial properties measured at the end of the experiment. Severe water stress did significantly decrease the height, number of leaves, and aboveground biomass of millet plants. Additionally, respiration, nematofauna trophic structure and abundance decreased as water stress increased. Lastly, bacterial feeders and plant parasitic 190nematodes were the most sensitive to severe water stress while fungal feeding nematodes remained unaffected. The results suggested that the intensity of water stress had more negative effects on soil basal respiration rather than soil microbial biomass.

The excessive application of mineral fertilizers in maize cultivation leads to progressive soil contamination in the long term and increases the cost of production. An alternative to reduce over-fertilization is to perform a partial replacement with microbes that promote nutrition and growth, such as Arbuscular Mycorrhizal Fungi (AMF). A pot experiment which was followed by two field experiments was performed with and without the application of indigenous AMF in combination with five nitrogen–phosphorus–potassium (NPK) fertilization rates (100% NPK = N120P60K60; 75% NPK = N90P45K45; 50% NPK = N60P30K30; 25% NPK = N30P15K15; control = N0P0K0). The objective was to investigate whether the soil application of indigenous mycorrhizal fungi inoculum combined with NPK fertilization can provide higher maize yields and soil-available N, P, and K than chemical fertilization can alone. The greenhouse results showed that the application of AMF with a 50% NPK treatment significantly increased the plant’s growth, root colonization, leaf chlorophyll content, and N, P, and K tissue content. The results from the field conditions showed that there was a highly significant yield after the treatment with AMF + 50% NPK. The study also revealed that mycorrhizal fungi inoculation increased the available soil N and P concentrations when it was combined with a 50% NPK dose. This suggests that the inoculation of fields with AM fungi can reduce the chemical fertilizer application by half, while improving soil chemistry. The results suggested that AMF inoculation can be used in integrated soil fertility management strategies.

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Rice (Oryza spp. L., 1753) is the most staple food cereal in Senegal. However, national production is low and cannot cover the country needs. Salinity limits rice production in Senegal River valley which is main rice growing area in Senegal. This study assessed salinity tolerance of 30 rice lines at vegetative stage in station of Senegalese Institute for Agricultural Research (ISRA) at Ndiol in Senegal River valley. Experimental design adopted was alpha lattice with three rehearsals. Observations were performed on plant height, main stem development and number of tillers. The level of salinity and pH in surface water, groundwater and soil were monitored. The results indicate that salinity affects plant height and tillering ability and among 30 lines, four were identified highly tolerant to salinity at vegetative stage. These are the varieties HK11-NDIOL-11-LON-1, D20-ART20-ARS-1, D56-ARS-NCRIB-1-1 and HK72-NIONO-5-1-1. The decision to incorporate these varieties in salinity tolerance breeding programs would depend on salt tolerance screening across all growing stages.

Maize is part of the essential food security crops for which yields need to tremendously increase to support future population growth expectations with their accompanying food and feed demand. However, current yield increases trends are sub-optimal due to an array of biotic and abiotic factors that will be compounded by future negative climate scenarios and continued land degradations. These negative projections for maize yield call for re-orienting maize breeding to leverage the beneficial soil microbiota, among which arbuscular mycorrhizal fungi (AMS) hold enormous promises. In this chapter, we first review the components relevant to maize-AMF interaction, then present the benefits of arbuscular mycorrhizal symbiosis (AMS) to maize growth and yield in terms of biotic and abiotic stress tolerance and improvement of yield and yield components, and finally summarize pre-breeding information related to maize-AMF interaction and trait improvement avenues based on up-to-date molecular breeding technologies.

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