INFECTIVITY OF MONOAXENIC SUBCULTURES OF THE ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS VERSIFORME ASSOCIATED WITH RI-T-DNA-TRANSFORMED CARROT ROOT

Glomus versiforme was associated in vitro with Ri-T-DNA-transformed ca rrot root and after 4 months of cultivation, numerous axenic arbuscula r mycorrhizal (AM) propagules were obtained. Three successive generati ons of spores and mycorrhizal root pieces were obtained by reassociati ng a 4-month-old root piece with a new carrot root. A biological test was conducted to assess the infectivity of the three generations of in oculum. Both for spores and mycorrhizal root pieces, a significant dec rease in infectivity was observed among the successive generations. My corrhizal root pieces however, exhibited, higher infectivity than spor es. These results show the possibility of maintaining AM fungi culture s in axenic conditions for a long time and raise questions about the l oss of infectivity among the generations. The necessity of maintaining the same strains in vitro and in vivo in two separate collections is discussed.