The Usefulness of Mycorrhizal Fungi to Mitigate Weaning Stress in Micropropagated Grapevine Plantlets

Large-scale mortality of in vitro raisedplantlets occurred during acclimatization، i. e. glasshouse hardening، and later at field transfer still has remained as a significant bottleneck in micropropagation. The usefulness potential of some arbuscular mycorrhizal fungi (AMF) to minimize mortality rate of three commercial grape rootstock genotypes during glasshouse acclimatization was studied. Inoculation was carried out using soil based inocula added below the root system per each plantlet. Of the three different AMF strains used، Glomus manihotis showed the highest survival rate (80. 15%) in the inoculated plants during hardening. All the inoculated plantlets exhibited morphological alterations such as higher vine length، leaf area and root length over the control. Beneficial effect of AMF inoculation on shoot growth resulted about 1. 6 times taller vines compared to the non-inoculated control plantlets. The biochemical analyses revealed that the amount of total chlorophylls in leaves and phenols in vines were increased significantly in the mycorrhizal plants. Though total phenolic compounds were significantly increased in the treated plants following inoculation، but inoculated plants with G. monosporum and G. manihotis showed higher phenols in their foliage. The present investigation revealed the integration of AMF association in tissue culture as a helpful strategy to minimize weaning stress and mortality rate of microplants during ex vitro acclimatization and may be utilized in commercial laboratories after verification of these results by the complementary experiments.