Use of arbuscular mycorrhiza for acclimatization of micropropagated plantlets of melon, oregano, artichoke and spanish broom

Micropropagation has been extensively used for rapid multiplication of many important plant species. However, its more widespread use is restricted by the often high percentage of plants lost or damaged when transferred to ex vitro condition. In this context, a biotechnological tool that allows to overcome these problems is the manipulation of mycorrhizas, because the establishment of the symbiosis with the root system of micropropagated plants gives positive effects on survival and growth rates after acclimatization. The purpose of this investigation was to evaluate the influence of mycorrhiza on plant survival and on growth responses of four different species of micropropagated plants: Cynara cardunculus L., Cucumis melo L. var. inodorus, Origanum vulgare L. subsp. hirtum and Spartium junceum L. Plants were micropropagated, multiplied and rooted in vitro in appropriate media under the following conditions: temperature 23° C photoperiod l6 h light intensity 60 μE s-1 m-2. After rooting, the plants were transferred to the greenhouse in pots containing a sterile mixture of peat and perlite and inoculated with the fungus AM Glomus viscosum under controlled conditions. The number of plants surviving transplantation was recorded after 1 month. Fresh and dry weight of shoot and root systems were determined after 60 days growth for each plant. Leaf area index and shoot/root fresh weight ratio were also calculated. Mycorrhizal development was evaluated microscopically on subsample. Survival rate was variable between the four tested species. Mycorrhizal colonization improved the growth of all the micropropagated species. These results corroborate the key role of arbuscular mycorrhiza in inducing beneficial changes in the general developmental of micropropagated plants.