Novel Ecofriendly Approaches for Controlling Soil Borne Fungal Pathogens: A Review
Abstract
The application of chemical fungicides for controlling soil borne plant pathogens is rapidly increasing due to their potential to deliver desirable results in a short span of time. However their rampant use has made many invasive plant pathogens resistant to any chemical control making them way harder to eradicate or eliminate as compared to the past days. The uncontrolled use of chemical fungicides is also causing soil toxicity and water pollution leading to several health hazards. The aim of the review article is to highlight the recent advancements in the field of eco-friendly disease management using the extracts obtained from natural resources and biologically active antagonistic organisms. The review article highlights the management of Black scurf disease (Rhizoctonia solani) in Potato using Bacillus subtilis V26 strain and by using a mixture of cattle manure and date palm compost. Biological control of Fusarium wilt of tomato (Fusarium oxysporumf.sp. lycopersici) by the application of endophytic bacterial isolates from Silver Leaf (Solanum elaeagnifolium) has been also mentioned. The review includes the management of Late blight of potato (Phytophthora infestans) using antagonistic Poplar (Populus nigra) bud extracts and peptide extracts obtained from Common Horsetail (Equisetum arvense). The review article also mentions the innovative method of management of Black shank disease of tobacco (Phytophthora parasitica var. nicotianae) by colonization of tobacco roots with Paenibacillus polymyxa C5 strain. As per the article, Foot rot of rice or rice bakanae (Fusarium moniliforme) can be effectively managed by the application of antifungal Surfactin-A extracted from Bacillus subtilis NH-100 and NH-217 strains. The article highlights the potential of the Bacillus subtilis RH5 strain as a bioformulation for controlling Sheath blight of rice (Rhizoctonia solani). The extracts and the antagonistic biocontrol agents can be used in the effective management of some economically important soil-borne plant diseases as a novel, innovative and environmentally safe approach.
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Introduction
Soil borne diseases are considered a major hurdle in crop production. Soil borne plant pathogens such as Rhizoctonia spp., Fusarium spp., Sclerotinia spp., Verticillium spp., Pythium spp., and Phytophthora spp. can cause around 50%–75% yield loss for many crops such as wheat, cotton, maize, vegetables, fruit and ornamentals as reported to date [1, 2, 3]. Soil-borne fungal pathogens like Rhizoctonia, Fusarium, Pythium, Verticillium, Phytophthora, Sclerotinia, Rosellinia, etc. exist in the form of dormant propagules or spores and start growing when the micro-environment becomes favorable [7]. Infected seeds act as a primary source of infection that travels from one place to another, crossing demographic boundaries [7].
The significant problems caused by soil borne pathogens in crop production include reduced crop performance, decreased yield, and higher production costs. The threats of soil borne disease epidemics in crop production, high cost of chemical fungicides and development of resistance towards fungicides, climate change, new disease outbreaks and increasing environmental concerns along with soil health are becoming increasingly evident. Inorganic farming most of the soil borne fungal diseases can be controlled by stimulating bio-diversity in and above the soil, by feeding soil life with organic soil amendments and good soil management [4]. The review article summarizes innovations for controlling soil borne pathogens using antagonistic microorganism and plant extracts.
Conclusion
/ FUTURE PROSPECTS The review article efficiently demonstrates the potential of non-chemically synthesized products (plant extracts and bioformulations) in the management of some of the most devastating diseases like Late blight, Fusarium wilt, Black shank and Sheath blight occurring on economically important crops such as potato, tomato, tobacco and rice respectively. The exact mechanisms behind the management of Black scurf of potato using Bacillus subtilis V26 and date palm compost; biological control of Fusarium wilt using bacterial isolates from Silver Leaf stems and management of Late blight of potato using poplar bud extracts and peptide extracts of Common Horsetail have been clearly described in the research papers of some scientists. However, besides the mechanism of biofilm formation by the antagonists, the principal biocontrol mechanism behind the management of Black shank of tobacco by colonization of roots by Paenibacillus polymyxa C5 strain; biocontrol of foot rot in rice by Surfactin-A and management of Sheath blight of rice by RH5 strain of Bacillus subtilis have not been clearly elaborated. Therefore, comprehensive research works are needed on those areas for making them commercially successful. The innovative approaches mentioned in the review article can be emphasized upon for their commercialization so that the farmers across the globe can quickly switchover from chemically synthesized fungicides to the eco-friendly bioformulations for effective management of major soil-borne plant diseases.
