In agriculture, control of plant pathogens can be done by chemical or by biological methods. Both of them act on pathogen population as well as on rhizospheric microflora. Research have been done in order to study the structure of rhizospheric fungal community of two soybean cultivars under the influence of chemical and biological agents for the control of gray mould. A green house experiment was designed to compare the structure of fungal rhizospheric microflora of soybean cv. PR91M10 sensible to gray mould and PR92B62 resistant, treated with systemic and contact fungicides, as well as with four fungal preparations from genera Botrytis, Trichoderma and Penicillium administrated on plants and in soil. The taxonomic composition of fungal community was assessed by plating soil fragments on water agar and identifying the developed structures. A total number of 21 genera were identified for sensible soybean cultivar PR91M10 and 18 genera for resistant cultivar PR92B62. The frequency registration allowed the genera to be classified as constant accessory and accidental. Thus, the status of each taxon was the same or modified as a function of the nature of treatment (with biological or chemical control agents) or method of administration (on leaves or in soil). Apart of significant influence of fungal extracts on improving plant health, the ecological analysis of the rhizospheric fungal communities assessed the influence of biological control agents provided by selected microbial strains, on natural microflora composition and number. The use of water agar substrate allowed as to cultivate, identify and make photographs to four predaceous species of genera Arthrobotrys, Dactylaria, Nematoctonus and Harposporium, same of them rarely isolated on other usual media. The development of ring form fungal traps or adhesive knobs and haustoria-like hyphae was possible to be monitored as well as trapped nemathods digestion by predaceous fungi, demonstrating the dynamic relationships between microflora and fauna in the rhizosphere of cultivated plants such as soybean under the influence of control agents for gray mould.

fungi; rhizosphere; resistance; soybean; biological control

Presentation: oral