Searching for Novel Fungal Biological Control Agents for Plant Disease Control Among Endophytes

Abstract

There are increasing efforts aiming to utilise endophytes as biological control agents (BCAs) to improve crop production. However, reliability remains a major practical constraint for the development of novel BCAs. Many organisms are adapted to their specific habitat; it is optimistic to expect that a new organism added can find a niche or even out-compete those adapted and already present. Our approach for isolating novel BCAs for specific plant diseases is therefore to look in healthy plants in a habitat where disease is a problem, since we predict that it is more likely to find competitive strains among those present and adapted. In vitro inhibitory activities often do not correlate with in planta efficacy, especially since endophytes rely on intimate plant contact. They can, however, be useful to indicate modes of action. We therefore screen for in planta biological activity as early as possible in the process in order to minimise the risk of discarding valuable strains. Finally, some fungi are endophytic in one situation and pathogenic in another (the mutualism-parasitism continuum). This depends on their biology, environmental conditions, the formulation of inoculum, the health, developmental stage and cultivar of the host plant, and the structure of the plant microbiome .

Interaction between endophytic Proteobacteria strains and Serendipita indica enhances biocontrol activity against fungal pathogens

“…On the basis of the accelerated depletion of the currently available fungicides, and the huge amounts of crops affected worldwide by plant pathogens, the upcoming generation of bioinoculants shall combine plant growth enhancement with biological control of plant pathogens (Collinge et al 2019). Notwithstanding that these bacterial strains harbor genes involved in biocontrol of plant diseases, bacteria inoculated individually were generally not able to control fungal pathogens.…”

Fusarium Head Blight Modifies Fungal Endophytic Communities During Infection of Wheat Spikes

“…Since these microorganisms possess similar characteristics and share essentially the same biological niche as pathogens, it is relevant to understand their relationships and behaviour during disease outbreaks [16]. Moreover, some of these microorganisms may have the potential to be exploited in disease control as biological alternatives or to complement current control options [17]. If fungal endophytes were to be exploited as a new source of biocontrol agents, it would necessitate a thorough understanding of their behaviour when the pathogen arrives and the disease occurs [18].…”

Beneficial Endophytic Bacteria-Serendipita indica Interaction for Crop Enhancement and Resistance to Phytopathogens

“…secretion of antifungal compounds, mycophagy) have also been widely reported (Bonfante and Anca, 2009;Kobayashi and Crouch, 2009). Understanding and exploiting the association between different kinds of beneficial microorganisms, together with the management and engineering of the plant microbiome, may lead to improving soil fertility, crop productivity, and biological control of plant pathogens (Berg, 2009;Collinge et al, 2019;Compant et al, 2019).…”

“…Only few studies have demonstrated in vitro that particular bacterial strains can be detrimental for the growth of S. indica (Varma et al, 2013) or in contrast have stimulatory effects, like strain WR5 of Azotobacter chrococcum, which enhanced mycelial growth and sporulation of S. indica in vitro (Bhuyan et al, 2015). In the last few years, some researchers have developed co-inoculations (microbial consortia) of fungi and bacteria, searching synergisms between two beneficial microbes (Artursson et al, 2006;Collinge et al, 2019). Special focus has been laid on the combination of S. indica with PGPR.…”