**4. Drought tolerance**

*Mycorrhizal Fungi - Utilization in Agriculture and Forestry*

their nutritional requirements (**Figures 2** and **3**) [9].

resistance to host plant and infective organisms [10].

and productivity in plant communities [14].

**3. AMF as biofertilizers**

reports supported that AMF was essential constituents in predominant land plants in most taxa in all the ecological niches for ages. The Glomeromycota are a distinctive obligate biotrophic fungi that majorly comprises AMF related in symbiosis with many Embryophytes [7]. Nevertheless, certain mycoheterotroph plant species on AMF symbiosis turned in to obligate parasites having completely lost plastid genetic apparatus, photosynthesis genes with secondary functions, NADH dehydrogenaselike genes and photosynthesis genes. As another diversity was seen in plant taxa such as Brassicacea (or Cruciferae) and Chenopodiaceae, where they have shown asymbiotic interaction with AMF and these plants developed other strategies for

Many active or dormant strains of bacteria or fungi or in combinations are used diametrically or collaterally to activate the rhizo-microbiome and trigger the nutrient supply from soil to plants that would ultimately result in enhancement of crop yields. These microbial strains are broadly termed as biofertilizers, bioinoculants, agricultural inoculants, soil inoculants, or microbial inoculants. These bio-inoculants with unique merits are highly encouraged globally and are earning prominence in modern agricultural customs, practices and maneuvers contrasting to other conventional or synthetic pesticides and fertilizers. These biofertilizers are safe to handle, are required only in small quantities as they capable of fast replication, their action can be leveraged or optimized based on their incumbencies, decompose quickly with negligible ill effects to the environment and show lower

Plant growth promoting and disease suppressing microbial inoculants such as *Azospirillum, Bacillus, Pseudomonas, Rhizobium, Serratia, Stenotrophomonas,* and *Streptomyces, Ampelomyces, Coniothyrium, Glomus,* and *Trichoderma are* extensively examined and analyzed for their mechanism of action and regulatory gear. Even though multiple categories of biofertilizers are at hand, the AMF is reported of manifold advantages and graded high for soil health and crop productivity [11]. Studies have shown comparative progress where plants get better nourishment with greater AMF colonization than that of the non-mycorrhizal plants even with conditions like mineral deficiency and abiotic stress. AMF establishes symbiotic interconnection with many different types of Plants or the other way round, that leads to the formation of common mycorrhizal networks (CMNs) and such mycorrhizal interactions are exceptionally valuable for healthier plant growth and yield in most of the scenarios [12]. Certain AMF show specific combinatorial benefits with specific types of plant species from all types of geographical locations that can result in positive mycorrhizal growth response (MGR) and this is a progressive mutual adaptation that did not correlate with phylogenetic lineage patterns relevant to variant species [13]. Contrarily, some studies though agree with the functional specialization of AMF, proved that such incidence is a flexible phenomenon where plant species are required to show compatibility with at least a few AMF. This scenario with minimal host specificity and broad functional specialization encourages vast biodiversity

Rampant use of inorganic fertilizers, herbicides, and fungicides are causing multiple injurious health risks to every living organism by hazardous impacts on the quality of food, soil, air, and water systems [15]. Over the years, many investigations have proven the efficacy of AMF for best agricultural production compared to other synthetic or chemical fertilizers under the prevalent stressful conditions, as

**34**

addressed below.

Drought is the scarcity of water in soil for prolonged durations affects plant growth. It has severe implications on the entire plant biorhythm and growth at every notch. Deficit water supply to roots causes oxidative stress due to anomalies in transpiration [16], affects enzyme activity, ion uptake, and nutrient assimilation [17]. Many investigations have evidenced that AMF can allay drought stress in varied crop like wheat, barley, maize, soybean, strawberry, and onion [18]. This remarkable tolerance is reasoned essentially due to the extra-radical hyphae of AMF that has the capability of vast area spread [19]. Further, the osmotic adjustment, stomatal regulation, enhanced proline, and glutathione level are exhibited to have augmented root efficiency, leaf area index, and biomass under the instant drought conditions and against severe environmental conditions. Reports have demonstrated that the enhancement in growth and photosynthesis in C3 (*Leymus chinensis*) and C4 (*Hemarthria altissima*) plant species through up-regulation of antioxidant system by AMF symbiosis (**Figure 4**) [20].

#### **Figure 4.**

*2017 California spring trials. Coreopsis plants (image 1) inoculated with AMF (left) showed better tolerance than plants without AMF under same drought stress. Coreopsis plants (image 2) treated with AMF showed improved top growth and root system development (left) than that without AMF inoculation (right) (photo courtesy: Mycorrhizal applications @ GPNMAG.COM 2018).*
