Effects of fertilizers and arbuscular mycorrhizal fungi on the post-vitro growth of micropropagated strawberry

A 5-wk factorial experiment was conducted to examine the effects of osmocote (18N:11P:10K; commercial controlled-release fertilizer), rock phosphate and 3 species of arbuscular mycorrhizal fungi on the growth of the strawberry cultivar Senga Sengana in a peat-sand-vermiculite substrate. Three Glomus species, G98 (probably G intraradices), G128 (an undescribed species) and G geosporum were compared. G98 and G128 significantly increased shoot dry weights compared with the non-mycorrhizal control. Levels of root colonization by G98 and G128 were significantly greater than by G geosporum. The addition of both fertilizer types significantly increased shoot dry weights. Neither osmocote (0.5-2.0 g/l) nor rock phosphate (1.0-5.0 g/l) addition had a significant effect on colonization by the 3 fungi. An osmocote fertilizer applied at 25% of the minimum recommended commercial rate to mycorrhizal plants was sufficient to produce equivalent dry matter yields as non-mycorrhizal plants receiving the full application of osmocote. All 3 fungal species significantly increased the stolon number per plant when compared with the non-mycorrhizal controls. Results clearly show that healthy mycorrhizal strawberry plants can be produced at weaning using commercial or reduced rates of osmocote or a rock phosphate formulation.