The Influence of Trichoderma harzianum Rifai T-22 and Other Biostimulants on Rhizosphere Beneficial Microorganisms of Carrot

Abstract

The principles of good agricultural and horticultural practice, which consider both giving environmental protection and high yielding of plants, require modern cultivation methods. Modern cultivation of horticultural plants uses, for example, cover crops, living mulches, plant growth-promoting microorganisms (PGPMs), plant growth regulators (PGRs) and other biostimulants protecting the soil against degradation and plants against phytopathogens and stress. The purpose of field and laboratory studies was to determine the effect of Trianum P (containing Trichoderma harzianum Rifai T-22 spores), Beta-Chikol (a.s.—chitosan), Timorex Gold 24 EC (based on tea tree oil) and fungicide Zaprawa Nasienna T 75 DS/WS (a.s.—tiuram 75%) on the health of carrot (Daucus carota L.) plants and the microorganism population in the rhizosphere of this plant. Moreover, the antagonistic effect of rhizosphere fungi on selected carrot fungal pathogens was determined. Laboratory mycological analysis allowed one to determine the qualitative and quantitative composition of fungi colonizing the underground parts of carrot plants. In addition, the total population of fungi and bacteria was determined (including Bacillus sp. and Pseudomonas sp.) based on the microbiological analysis of the rhizosphere soil. The application of the plant growth-promoting fungus (Trichoderma harzianum T-22), chitosan and tea tree oil positively influenced the growth, development and health status of carrot plants. T. harzianum T-22, chitosan and fungicide most effectively protected carrots against infection by soil-borne fungi from the genus Alternaria, Fusarium, Haematonectria, Sclerotinia and Rhizoctonia. The rhizosphere population of Bacillus sp. and Pseudomonas sp. in the treatments with Trianum P or Zaprawa Nasienna T 75 DS/WS was bigger than in the other experimental treatments. A reverse relationship was observed in the population of rhizosphere fungi. T. harzianum T-22, chitosan and tea tree oil promoted the growth of antagonistic fungi (Albifimbria sp., Clonostachys sp., Penicillium sp., Talaromyces sp. and Trichoderma sp.) in the carrot rhizosphere. Antagonistic activity of these fungi towards Alternaria dauci, Alternaria radicina, Sclerotinia sclerotiorum and Rhizoctonia solani was higher after the application of the preparations compared to control. Consequently, Trianum P, Beta-Chikol and Timorex Gold 24 EC can be recommended as plant biostimulants in ecological agricultural production, including Daucus carota cultivation.

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

“…They lead to the accumulation of harmful microorganisms, including phytopathogens and pesticides and their derivatives in soils and plants [4,5]. Suitable conditions for the growth and development of plants can be achieved by maintaining high activity and biodiversity of beneficial soil microorganisms, by more complex agricultural management, and by applying biological plant protection [6][7][8][9]. In modern agriculture, it is possible to use biostimulants that protect the soil against degradation and plants against phytopathogens and stress.…”

“…This is associated with the necessity to obtain a large and good-quality root yield [10,15]. The health-promoting properties of root vegetables, including scorzonera, is determined, among others, by physical and biochemical properties of the arable environment [10,16] and biodiversity of soil microorganisms, especially the presence of soil-borne pathogens [6,17,18]. Despite the relatively rare cultivation of scorzonera, information about infectious agents that threaten this species is available in the literature.…”

“…Therefore, appropriate methods of growing Scorzonera hispanica should be used, which would limit its infestation by phytopathogens. Such conditions can be obtained by using biostimulants, PGPMs (plant growth-promoting microorganisms) and PGRs (plant growth regulators) in plant cultivation [6,23,24]. They protect the soil from degradation and plants from phytopathogens and stress [23,25].…”

“…Useful microorganisms applied as biostimulants include, among others, bacteria: Pseudomonas spp., Bacillus spp., Arthrobacter spp., Enterobacter spp., Rhodococcus spp., Ochrobactrum spp., Serratia spp. [23,[33][34][35] and fungi: Trichoderma harzianum, Trichoderma reesei, Trichoderma atroviride, Heteroconium chaetospira, Claroideoglomus etunicatum, and Glomus intraradices [6,25,[36][37][38]. These microorganisms, inhabiting the rhizosphere soil and colonizing plant roots, belong to the PGPM (plant growth-promoting microorganisms) group [6,23,24,[33][34][35].…”

“…[23,[33][34][35] and fungi: Trichoderma harzianum, Trichoderma reesei, Trichoderma atroviride, Heteroconium chaetospira, Claroideoglomus etunicatum, and Glomus intraradices [6,25,[36][37][38]. These microorganisms, inhabiting the rhizosphere soil and colonizing plant roots, belong to the PGPM (plant growth-promoting microorganisms) group [6,23,24,[33][34][35]. Among them, we can distinguish PGPR (plant growth-promoting rhizobacteria) [23,24,33] and PGPF (plant growth-promoting fungi) [6,25,38].…”