TIME-COURSE OF APPRESSORIUM FORMATION ON HOST PLANTS BY ARBUSCULAR MYCORRHIZAL FUNGI

Appressorium formation in arbuscular mycorrhizal fungi was monitored on the roots of three host plants over periods up to 156 h. The first appressoria were formed by Glomus mosseae within 36 h after the beginning of the interaction with Ocimum basilicum and Helianthus annuus. The first arbuscules were formed by G. mosseae and Glomus A6 within 42 and 48 h respectively, after their inoculation on H. annuus. The importance of the present data for the study both of the early events of recognition in arbuscular mycorrhizal symbioses and of infectivity of the different endophytes is discussed.