Below-ground-above-ground Plant-microbial Interactions: Focusing on Soybean, Rhizobacteria and Mycorrhizal Fungi

Abstract

Introduction:Organisms seldom exist in isolation and are usually involved in interactions with several hosts and these interactions in conjunction with the physicochemical parameters of the soil affect plant growth and development. Researches into below and aboveground microbial community are unveiling a myriad of intriguing interactions within the rhizosphere, and many of the interactions are facilitated by exudates that are secreted by plants roots. These interactions can be harnessed for beneficial use in agriculture to enhance crop productivity especially in semi-arid and arid environments.The Rhizosphere:The rhizosphere is the region of soil close to plants roots that contain large number of diverse organisms. Examples of microbial candidates that are found in the rhizosphere include the Arbuscular Mycorrhizal Fungi (AMF) and rhizobacteria. These rhizosphere microorganisms use plant root secretions such as mucilage and flavonoids which are able to influence their diversity and function and also enhance their potential to colonize plants root. Natural Interactions between Microorganisms and Plant:In the natural environments, plants live in interactions with different microorganisms, which thrive belowground in the rhizosphere and aboveground in the phyllosphere. Some of the plant-microbial interactions (which can be in the form of antagonism, amensalism, parasitism and symbiosis) protect the host plants against detrimental microbial and non-microbial invaders and provide nutrients for plants while others negatively affect plants. These interactions can influence below-ground-above-ground plants’ biomass development thereby playing significant role in sustaining plants. Therefore, understanding microbial interactions within the rhizosphere and phyllosphere is urgent towards farming practices that are less dependent on conventional chemical fertilizers, which have known negative impacts on the environments.Below Ground Rhizobacteria Interactions Alleviate Drought Stress:Drought stress is one of the major factors militating against agricultural productivity globally and is likely to further increase. Belowground rhizobacteria interactions could play important role in alleviating drought stress in plants. These beneficial rhizobacterial colonize the rhizosphere of plants and impart drought tolerance by up regulation or down regulation of drought responsive genes such as ascorbate peroxidase, S-adenosyl-methionine synthetase, and heat shock protein.Insights into Below and above the Ground Microbial Interactions via Omic Studies:Investigating complex microbial community in the environment is a big challenge. Therefore, omic studies of microorganisms that inhabit the rhizosphere are important since this is where most plant-microbial interactions occur. One of the aims of this review is not to give detailed account of all the present omic techniques, but instead to highlight the current omic techniques that can possibly lead to detection of novel genes and their respective proteins within the rhizosphere which may be...

Rhizobium Inoculation Drives the Shifting of Rhizosphere Fungal Community in a Host Genotype Dependent Manner

“…Almost 70% of the total P acquired by rice enters symbiotically through AMF (Yang et al, 2012). These soil fungal networks are also more resilient than bacterial networks under drought conditions, and some might tolerate disturbances (de Vries et al, 2018;Igiehon and Babalola, 2018). Fungal and bacterial interactions affect plant participation in symbiotic relationships with mycorrhizal fungi, which further reinforces that multiple positive interkingdom interactions exist in plant-associated microbiota (Garbaye, 1994).…”

Straw input can parallelly influence the bacterial and chemical characteristics of maize rhizosphere

“…Because the members of phylum Proteobacteria have been reported to facilitate the horizontal transfer of genes related to photosynthesis, its high abundance is particularly vital for crop growth [47]. Furthermore, many taxa within this phylum exhibit disease-suppression activity, such as defending plant roots from fungal pathogen infection, which may improve the health of plant and soil [27]. In a previous study, during crop residue decomposition, the amount of easily decomposable compounds is positively related to the stimulation of Proteobacteria [48].…”

“…Wang et al (2017) also found that the soil diazotrophic community was influenced more by the soil type and associated characteristics than by crop's roots [57]. The richness and abundance of microorganisms in the rhizosphere can be determined by the plant, while the microbial diversity was strongly influenced by other ecological changes [27]. There are some relations between rhizosphere bacteria, plant roots, soil and other factors, but how they affect each other, need further research.…”

“…In a previous work, we found that root morphology, growth, and architecture were significantly influenced by biochar addition [25]. As cascade events, thus facilitated root growth by straw input may stimulate root secretions and consequently influence the information communicated and energy transferred between the plants and soil within the rhizosphere [26][27][28]. Besides the nature of root exudates, metabolite composition in the rhizosphere also is governed by the secretions from rhizobacteria, fungi and other soil organisms [29].…”

Alfalfa Powder Affects Soil Nutrient and Walnut Dry Matter Accumulation under Drought

“…Such constant and persistent low nutrient contents and water supplies reduce the biological production of aboveground plants and vegetation coverage, which would diminish C inputs to the soil and inactivate nutrient cycling in mountainous and hilly areas with poor soil (Potthast et al, 2012; Shimoda and Koyanagi, 2017; Willcock et al, 2014; Zhiyanski et al, 2016). Ecologists and agronomists have tried to increase soil C inputs and promote geochemical cycling in a variety of ways to prevent soil infertility, such as by adding high‐efficiency C sources (Yu et al, 2018), microbial fertilizers (Wu et al, 2018; Igiehon and Babalola, 2018), and soil improvement agents (Dannehl et al, 2016; Kathijotes et al, 2016); planting green manure (GM); and covering the soil with straw (He et al, 2018). The addition of plant materials is an important soil improvement practice in mountainous and hilly areas.…”