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Establishment of the fungal entomopathogens Beauveria bassiana and Beauveria brongniartii as endophytes in pedunculate oak seedlings and different methods of their detection

Aside from their natural occurrence in the soil, fungal entomopathogens can be established as endophytes, naturally or by inoculating in plants. Aim of this research was to investigate possible endophytic growth of entomopathogenic fungi Beauveria bassiana and Beauveria brongniartii in pedunculate oak (Quercus robur L.) leaves and roots, in order to make a basis for further research of possibilities in regulation of insect populations by endophytic growth of these fungi. An inoculation method based on infiltration of leaves and drenching the soil by using B. bassiana and B. brongniartii blastospores suspensions resulted in no endophytic colonization of pedunculate oak seedlings within 5 weeks after inoculation. Techniques for detection included visualization of fungal structures by using common dyes, and immunological techniques with the use of polyclonal antibodies labelled with a fluorescent marker, investigated by fluorescence and confocal microscopy. Repeated shorter method of immunofluorescence labelling for a more rapid detection after 5 months discovered established B. brongniartii hyphae on the oak root surface, but not within their tissue. Except the fact that this fungi are not able to grow systematically within pedunculate oak plant tissue, this research revealed that endophytic behaviour of entomopathogenic B. bassiana and B. brongniartii in plants can be detected much quicker, and studies of introduced fungal endophytes can be much more improved. Also, this research demonstrated a long-term persistence of the applied B. brongniartii in the soil and therefore its potential as microbial agent in biological control of insect pests in soil.

Beauveria bassiana, Beauveria brongniartii, endophytes, entomopathogens, immunofluorescence microscopy, Quercus robur

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