Microbials In Agriculture: A Current Review on the Perspectives and Challenges for Large Scale Implementation

The Food and Agriculture Organization (FAO) estimates the world’spopulation to reach about 8.5 billion people in 2025 (1). Due to this rapid growth rate in population (approximately 1.05% per year), malnutrition has emerged in roughly 2.4 billion individuals across the world (2). Global food production will need to increase by at least 60% if food security is to be achieved by the year 2050 (3). In addition, an increase in agricultural productivity is also essential in realizing numerous sustainable development goals (SDG) including zero hunger (SDG 2), no poverty (SDG 1), and good health and well-being (SDGs 1 and 2), which can all ultimately benefit life on land (4). It is thus important to upgrade existing cropping systems, despite present limitations of limited resources and reduction in arable land.

Agricultural production, however, faces a number of unforeseen environmental issues such as drought, heatwaves and flooding. More significantly, plant pests and pathogens cause a range of plant diseases significantly reducing agricultural output (5). For example, farmers face major food losses annually, ranging from 21.5% in wheat, 30.3% in rice, 22.6% in maize, 17.2% in potato, and 21.4% in soybean, due to pests (5). Downstream effects to human health are inevitable due to decreased yields, loss of species variety and increase in pest mitigation costs (5). Thus, along with an increase in production, a major reduction in food loss due to pests and pathogens is also required.

Currently, agrochemicals are used to increase yields and scale up crop productivity with the goal of intensive farming (4). This is done in attempt to increase agricultural production on current agricultural land, rather than an expansion in arable surface. Farmers rely on traditional agricultural practices which use inorganic fertilizers, pesticides, and other chemical inputs, as they substantially increase yield without the need of more land. Among all, phosphorus and nitrogen fertilizers are commonly used, in combination with herbicides and pesticides to help maintain crop productivity and yields, in addition to managing invasive plants, diseases, and insects (4).

The continuous and excessive use of agrochemicals, however, has led to increased soil salinity and toxicity, hardening of soil, decreased nutrient carrying capacity and water logging (6,7). Additional issues in the form of pesticide resistance prompting the use of higher doses which lead to aggressiveness of disease and pathogen mutations, have pronounced negative environmental impacts and serious implications for food security (7). Not only do they have direct effects on the environment, but they can also be damaging to human health indirectly or directly. Chemical pesticides find their way into drinking water systems and food products, exposing humans to high levels of toxicity. According to a study published in 2014, many chemical pesticides used throughout the world are far more harmful to human health and the environment than previously assumed (7). A well-known example is DDT which was the first synthetic insecticide to be produced. DDT is highly effective against insects and plant pathogens but was recently suspected to be a probable human carcinogen (7). Numerous other studies have linked chemical pesticides to cancer, Alzheimer’sdisease, ADHD and birth defects (7). In addition to this, the rising cost of pesticides particularly in less developed countries, and customer demand for pesticide-free food has prompted a search for alternatives. Many fastidious diseases also do not have chemical solutions as they are ineffective or do not exist. Thus, for all the above reasons and disadvantages of existing farming systems, it is necessary to shift to using of sustainable practices for increased crop output. Sustainable practices have the potential to offer long-term solutions to secure global food security (7). One of the most promising sustainable practices that is being implemented today is the use of microbials for crop growth promotion/ protection. Microbials are a class of biologicals that use living microorganisms for crop protection (6,7). It is a form of biological control that is preventative and/or curative indirect pest control. In addition to crop protection, they work together with the plant microbiome to help improve overall plant growth, nutrient efficiency, and stress tolerance (4,6). Microbial products contain organisms from most microorganism genera (viruses, bacteria, fungal pathogens, yeast and protozoa) (11). Bacteria are the most commonly used microbials due to their lower costs and ease of usage as compared to fungal biological control agents (11).

Microbial products have the potential to boost crop yields and supplement or replace agricultural chemicals and fertilizers (4,6,11). As opposed to chemical pesticides, microbials are made from naturally occurring materials (11). It presents as avery appealing alternative because it would drastically minimize the consumption of agrochemicals. Many companies have begun to use single or multiple microorganisms as biocontrol or biofertilizer products, as well as develop carrier-based inoculants of beneficial strains (12). Large-scale field trials have shown an improvement in crop yield of 10–20% on commercially important crop plants (11). Currently, microbials makeup the largest part of the biologicals market and are expected to grow up to 60% of the biological control market by 2025 (12).

Growing consumer interest inorganic agriculture, the reduction of synthetic products, and the economic potential of rising countries like India are all major growth factors in the development of the microbials market (14). However, despite the benefits and potential of agricultural microbial products, according to a recent study on microbials, "the scientific literature abounds with numerous potentially highly helpful strains that did not arrive on the commercial market" (15). It was found that, approximately 72% of biocontrol company endeavors failed over a 30-year period ending in 2002 (16).

This can be attributed to many challenges faced in the development of microbial products. Usually, the development of a commercial microbial product is a lengthy process that necessitates a high level of expertise and close collaboration among experts from numerous domains (13). The research domain includes strain isolation, efficiency testing in vitro and in vivo, and trials in natural settings. Following this, the product must be produced on a commercial scale, conserved for storage, and prepared to assure biocompatibility in order to be delivered commercially. Only then, these procedures could be patented for large scale implementation. Even the registration process appears to be an issue as, large number of patents are issued, but only a few products have been registered (6,13). Failures are also caused by underestimating the expenses of creating and marketing microbial goods. The disparity between effective microbial strains and profitable agricultural products shows that unexpected challenges must be overcome.

Microbes will undoubtedly playa role in agricultural revolution in the coming decades, helping to fulfill the needs of a growing population. In order to realize the actual potential of microbes in agriculture, more research is required to improve industry standard of microbials and commercialization. Research and industry implementation always go hand in hand. In this review, we will discuss the major challenges faced by microbial production. To highlight this, amain research question with two sub questions is formulated to delve deeper into how these challenges are currently being overcome, in addition to the current microbials market. What are the challenges faced by translation of microbial products from lab to field? What is the importance of using microbials in enhancing plant growth promotion and crop protection? What are the existing solutions to the current challenges and future perspectives? While some reviews focus either on the research or industry side, this review aims to combine both as they would go hand in hand for ultimate improvement.