ARBUSCULAR MYCORRHIZAL INOCULATION OF MICROPROPAGATED STRAWBERRY AND FIELD OBSERVATIONS IN FINLAND

Micropropagated plantlets of strawberry (Fragaria x ananassa Duch Senga Sengana) were inoculated at the beginning of the weaning stage with a Glomus mosseae strain from Rothamsted Experimental Station (UK) or with 8 Finnish Glomus isolates, including 1 G mosseae isolate, 4 G intraradix isolates and 3 isolates of an unidentified Glomus species. After 8 wk (July 1990), inoculated plants were planted in the field: the most efficient fungi, ie G mosseae Rothamsted, Glomus sp V3 and Glomus sp V4, increased shoot growth several-fold during the weaning stage. Growth responses persisted throughout the 1 st yr in the field, and partly throughout the 2nd yr. Root colonization by different fungi was from near 0-60% during the weaning stage. In the 2nd yr, after overwintering, root colonization of inoculated plants ranged from 8-35% as compared to 4% for the control plants. The need for more precise studies of the influence of winter on the biological efficiency of introduced VAM fungi to strawberry roots is discussed.