PARAQUAT - A TOOL FOR THE QUICK DEVELOPME NT OF LATENT FUNGAL-INFECTIONS AND ENDOPHYTIC FUNGI

Detached winter wheat leaves without any symptom of fungal infection w ere thoroughly washed, surface desinfected, treated with paraquat (0.0 3-0.32% a.i.) and incubated on nutrient agar or in moist chambers unde r sterile conditions. Microscopic examinations showed that hyphae and yeast cells emerged from several stomata within 48-72 h after treatmen t. Fungal colonies developed on agar within the same period of time. M ore than 27 filamentous fungal genera and yeasts were identified durin g a wheat crop in healthy, green leaves. Non-treated leaves showed ver y few early emergences of fungi from stomata, but senescent leaves eve ntually yielded several fungal taxa observed after paraquat treatment. Similar observations were made on non-detached wheat leaves, and on d etached sugarbeet leaves. Paraquat also induced development of Fusariu m spp. from detached healthy winter wheat ears before or after heading . In grape berries, paraquat induced the development of latent infecti ons of Botrytis cinerea a few days after treatment. The usefulness of paraquat for the detection of endophytes and for the diagnosis of earl y and latent fungal infections in plants, and the possible involvement of endophytes in tissue senescence are discussed.