**4. The role of AMF in nutrients management**

The arbuscular mycorrhizal fungus can enhance the health of the soil and the plants by synthesizing metabolites and plant growth hormones, increasing the availability of essential vitamins to the plants in nutrient-deficient soils, and providing other ecological services. All these factors are further discussed.

#### **4.1 The function of arbuscular mycorrhizal fungi in soil nutrient uptake**

Numerous macro- and micronutrients are required by plants, including nitrogen (N), sodium chloride [NaCl], potassium (K), copper (C), calcium (Ca), iron (Fe), and zinc (Zn), amongst others [14]. Plants often take up these nutrients in an inorganic or fixed form from the soil or the air [6], before transferring them to the host plant. Conventionally, chemically produced fertilizer has been used to meet all the needs of plants because the quality of the soil's nutrients had decreased owing to overuse and pollution [15]. Unfortunately, the continuous application of these chemicals on farms has led to issues with pollution and the degradation of soil quality [14].

Therefore, the use of AMF in connection with other nutrients-solubilizing or -fixing microorganisms has recently been taken into consideration as a sustainable alternative to soil nourishment [9, 10, 16]. The soil's nutrients were mobilized to the host plant by AMF, through the mycorrhizal hyphae, which connect the plant roots to the soil. Several investigations into the mechanism of action of nutrient absorption and translocation with AMF have found that:


*Recent Advances in Plant: Arbuscular Mycorrhizal Fungi Associations and Their Application… DOI: http://dx.doi.org/10.5772/intechopen.108100*

absorption [12]. Similarly, Püschel [18], reported that the ability of mycorrhizal to modify their hyphal diameter by the size of the soil pore enables them to provide nourishment for plants regardless of soil texture.

Similarly, several researchers documented the beneficial impact of mycorrhizae on cassava plants with nutrient intake [8, 19–22]. For instance, AMF's contribution to Phosphate uptake was examined by Ndeko et al. [23]. They discovered that using AMF is suitable for enhancing cassava's phosphate nutrition in various soil types. The results of their experiment demonstrated that the root abundance and dry weight were increased by the inoculation of an unusual fungal strain (*Rhizophagus iregularis*). However, following AMF inoculation in unsterilized soil, the root dry weight dropped. They concluded that the *Rhizophagus iregularis* strain, particularly when the soil is not treated with phosphorus, increases the Phosphate uptake of the cassava plants [23].

Furthermore, the advantages of phosphorus nutrition were revealed using cassava and *Rhizophagus irregularis* inoculum. To determine whether the paradigm holds in tropical field settings, field tests were carried out in three areas utilizing varied AMF and cassava cultivars in both Kenya and Tanzania at varied Phosphorus fertilization levels. It was discovered that contrary to what the paradigm would have us believe, Cassava's ability to colonize AMF and respond to inoculation does not necessarily decrease as phosphorus availability rises. The obtained results showed that cassava genotypes and fungal availability play a role in maximizing inoculation responsiveness, which is not always the case in low Phosphorus availability settings [24].

Also, Poku [21], investigated how AMF could help cassava absorb more phosphorus from the soil. Phosphorus-fertilizer, AMF, Phosphorus + AMF, and Untreated (Control) were the four treatments used. In comparison to Phosphorusfertilizer treatment plots, the Phosphorus + AMF were significantly (p0.05) taller, and the Control and AMF-treated plots were significantly (p0.05) identical. At all four locations, the percentage of leaf Phosphorus was statistically comparable, with a grand mean was 0.4%. The content of Phosphorus in the leaves was significantly raised to 0.5% by adding AMF and Phosphorus + AMF to the soil. In comparison to control plots, tubers taken from Phosphorus + AMF-treated plot lines were meaningfully longer (p 0.05). when compared to the control samples, tuber length rose in plots treated with Phosphorus and AMF. The tuber yields on all soil treatments were higher than on control-treatment plots by a substantial amount (p 0.05). Phosphorus+AMF treated plots and AMF treated plots, however, had considerably higher values than P than the control plots. According to this study, cassava yield can be increased by utilizing AMF or Phosphorus+AMF in comparison to Phosphorus alone or untreated control plants and this can be used to maximize tuber yield [21].

Furthermore, in the work of Lopes et al. [25], they sought to ascertain whether co-inoculating micro-propagated cassava with AMF (*Glomus clarum*) and PGPBs (Plant growth promoting bacteria) improved greenhouse growth. Inoculated PGPB strains in the cassava variety "*BRA Pretinha III*" affected the number of glomerospores and mycorrhizal colonization, while *Glomus clarum* and PGPBs had synergistic interactions, the *Glomus clarum* and PGPBs combined inoculation promoted higher performance in cassava development with time like all the variants examined. Hence, Co-inoculating PGPBs and AMF can meet cassava's need for nitrogen, therefore, minimizing the need for nitrogen fertilizer [25].

#### **4.2 How arbuscular mycorrhizal fungi contribute to soil aggregation**

Sand, silt, and clay particles are bonded together to form aggregates of different sizes, and this arrangement is referred to as the soil structure [26]. Soil aggregation is essential to the health of the entire ecosystem because it serves as a major site for the exchange of water, gaseous, and nutrient flows as well as a significant source of carbon storage [27]. It is believed that fungal hyphae are one of the key binding agents involved in maintaining micro aggregates. However, intensive agricultural practices used today have significantly impacted soil structure by lowering aggregation stability [26, 27], via the following steps.

The first step is that the extraradical hyphae compress the soil physically as they ramify around plant roots, causing clay particles to reorient and ramification in macroaggregate pores [28], thereby affecting the plant water status, and contributing to the soils' cohesion and strength, particularly in drought conditions [29]. Also, the production of glomalin, which is a hydrophobic glycoprotein generated by AMF hyphae enables the hydrophilic fungal wall to stick to hydrophobic surfaces found on soil particles [30]. Glomalin production also increases carbon storage and availability, which has an impact on the microbial community, aggregate stability, and soil structure. Based on the design of the plant's roots and how they are connected to the fungus, glomalin promotes aggregation to varying degrees; the greatest impact on macro aggregation was observed with thin host plants' roots (0.2–1 mm in diameter) [28].

Furthermore, numerous authors have positively confirmed AMF's ability to lessen soil aggregation's detrimental impact on plant growth [28–31], but few studies have explicitly focused on cassava crops. One of these uncommon investigations was conducted by Morris et al. [31]. They were able to assess how AMF altered aggregate turnover durations. They demonstrated how AMF accelerated the production of large macroaggregates and slowed the dissolution of both big and small macroaggregates. In the presence of AMF, macroaggregates turnover increased. The internal aggregate organization suggested that although the accretion of soil to organic materials in the form of micro aggregates is a prevalent process, it is not the only one at work [31].

### **5. How arbuscular mycorrhizal fungi manages abiotic stressors**

Numerous abiotic stress studies have demonstrated how human activities associated with agriculture (such as irrigation, overuse of chemical fertilizers and pesticides deforestation, and waste material diffusion) have hurt the plant's growth, health, and output, leading to major production losses [12, 26, 27]. A general route is involved in how plants respond to stress; it begins with the membrane receptor acquiring the stress signal that culminates in the creation of genes, whose byproducts may defend the plant either directly or indirectly [32]. However, numerous investigations on AMF symbiosis have demonstrated that the contributing fungus typically uses several strategies to help the plant resist some abiotic stressors, including but not limited to salinity, heavy metal pollution, and drought [33]. Abiotic stressors are the main obstacle to achieving global food security since they significantly reduce crop production quality and quantity [30, 32, 33].

*Recent Advances in Plant: Arbuscular Mycorrhizal Fungi Associations and Their Application… DOI: http://dx.doi.org/10.5772/intechopen.108100*
