Actinomycetes for effective management of plant diseases and nematodes

Introduction

The quality of the plant products is impacted by a variety of biotic variables that affect the plants. Among them, soil-borne pathogens and plant parasitic nematodes are significant factors that restrict crop production. Utilizing microbial bioagents is a sustainable way to regulate the use of chemical methods due to their negative effects.

Numerous bacteria, fungi, and nematodes that are harmful to plants are controlled by a variety of rhizospheric microorganisms in plants. Actinomycetes are a class of gram-positive, spore-forming, aerobic microorganisms that are distinguished by having a high G+C content in their genomes. These organisms mainly grow by forming filaments. Due to the formation of several secondary metabolites which include antibiotics, enzymes and inhibitors, these are considered as the efficient biocontrol agents. By using a number of regulatory mechanisms, these metabolites regulate nematodes and plant pathogens.

Management of Plant Pathogenic Fungi by Actinomycetes

Actinomycetes produce antifungal peptides (AFPs) as secondary metabolites to combat fungi. These novel antibiotics belong to a naturally occurring class that is hydrophobic, amphiphilic (i.e., hydrophilic and lipophilic), and cationic. AFPs work in three different ways to prevent the growth of fungi, including the prevention of production of fungal cell walls, interfering with membrane components, and affecting intracellular targets such mitochondria and large nucleic acids.

Table 1. Antifungal Peptides in the Management of Fungal Pathogens

Management of Plant Pathogenic Bacteria by Actinomycetes

Many plant pathogenic bacteria can be controlled by the use of antibiotics. Many of the new antibacterial chemicals can be found in actinomycetes, which kill specific bacteria while having no negative effects on the host's tissues. Actinomycetes are responsible for producing 45% of the antibacterial chemicals found in microorganisms. Actinomycin, streptomycin, erythromycin, neomycin, etc. are some of these antibiotics.

Table 2. Antibiotics in the Management of Bacterial Pathogens

Management of Nematodes by Actinomycetes

Actinomycetes are the main tool for managing the nematodes. Actinomycetes produce numerous secondary metabolites which contain many nematicidal properties. Streptomyces spp. are the major group of actinomycetes which show activity against plant-parasitic nematodes by producing nematicidal metabolites.

Table 3.  Metabolites in the Management of Nematodes

Conclusion

Actinomycetes produce antifungal, antibacterial, and nematicidal antibiotics. These antibiotics are very helpful in addressing various problems, such as lowering the use of pesticides and soil toxicity, which has become a severe issue in recent years. As a result, it is essential to screen antibiotics from actinomycetes, which are the main mechanism for choosing the antibiotics that are effective against diseases and nematodes, in order to manage a variety of plant pathogenic microorganisms.

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Content contributors

• Sowjanya, B, ANGRAU, Bapatla
• Sankari Meena, K, ICAR-Indian Institute of Oilseeds Research, Hyderabad
• Vijayagopal, A, ANGRAU, Bapatla
• Prasad, R.D, ICAR-Indian Institute of Oilseeds Research, Hyderabad