Biostimulants Managed Fungal Phytopathogens and Enhanced Activity of Beneficial Microorganisms in Rhizosphere of Scorzonera (Scorzonera hispanica L.)

Abstract

The principles of good agricultural and horticultural practice, considering both environmental protection and high yielding of plants, require modern cultivation methods. In modern agriculture, it is possible to use biostimulants that protect the soil against degradation and plants against phytopathogens and stress. The purpose of 3-year field and laboratory studies was to determine the effect of Trichoderma harzianum T-22 and other biostimulants on the health status of scorzonera (Scorzonera hispanica L.) plants and microorganism populations in the rhizosphere of this plant. For this purpose, Biosept Active (a.s.—grapefruit extract), Timorex Gold 24 EC (based on tea tree oil), Trianum P (spores of Trichoderma harzianum Rifai T-22) and Zaprawa Nasienna T 75 DS/WS fungicide (a.s.—tiuram) were applied for the pre-sowing seed dressing of scorzonera cv. “Duplex”. The number of seedlings and the health status of scorzonera plants were determined during three growing seasons. In each year of the study, mycological analysis of seedling roots and roots after scorzonera harvest was conducted to establish the quantitative and qualitative composition of fungi colonizing these parts. Moreover, microbiological analyses of scorzonera rhzisphere soil were conducted and served as the basis to determine the total population of fungi and bacteria (including Pseudomonas sp. and Bacillus sp.). Antagonistic activity of rhizosphere bacteria Pseudomonas sp., Bacillus sp. and fungi was determined based on laboratory tests on selected scorzonera soil-borne fungal pathogens (Alternaria scorzonerae, Fusarium culmorum, Fusarium oxysporum, and Rhizoctonia solani). The experiments showed that Trianum P most effectively protected the roots of scorzonera against infection by Alternaria alternata, A. scorzonerae, Neocosmospora solani, Fusarium spp., Sclerotinia sclerotiorum, Rhizoctonia solani, and Botrytis cinerea. The rhizosphere population of Bacillus sp. and Pseudomonas sp. in the treatments with Trianum P or Zaprawa Nasienna T 75 DS/WS was larger than in the other experimental treatments. A reverse relationship was observed in the population of rhizosphere fungi. The application of grapefruit extract, tea tree oil and Trichoderma harzianum T-22 increased antagonistic activity of Pseudomonas sp., Bacillus sp. and selected saprotrophic fungi against soil-borne fungal pathogens, especially Alternaria sp., Rhizoctonia sp., and Fusarium sp. In summary, Biosept Active, Timorex Gold 24 EC and Trianum P can be recommended as plant biostimulants in Scorzonera hispanica cultivation.