Role of mycorrhizae on mineral nutrition of fruit trees

Citrus, cherry, plum, peach, apple, pear, nectarine, apricot, grape, kiwifruit, pomegranate, fig, olive and pistachio along with several native fruits such as wild black cherry and pecan are important temperate horticultural fruit species which are of keen interest to farmers. The roots of these species are naturally inoculated with mycorrhizal fungi. As the harvest time of fruits under Mediterranean climatic conditions is earlier than in many other regions, consequently there is an economic advantage for horticultural producers. Many soils in the Mediterranean region are deficient in plant nutrients (such as N, P, Zn, Fe and Mn) due to high clay and lime contents, often coupled with alkaline pH and limited water resources. To achieve an optimum plant growth, and obtain good fruit yield, chemical fertilizers are used. However, the excess use of chemical fertilizers negatively affects viable soil microorganisms, especially mycorrhizal fungi. Recent trends for the protection of the environment and the demand for healthy and ecologically-produced food, suggest minimal or no use of chemicals in agricultural production. Mycorrhizal fungi can promote plant root growth in marginally poor soils and under environmental stress. Mycorrhizal inoculation can contribute to the production of high quality fruit trees with balanced mineral nutrient uptake. In this work, the effect of mycorrhizal fungi on growth and nutrient uptake of micro-propagated cherry, grapevine, fig and banana rootstocks were investigated during acclimation and plant establishment. Banana and fig plantlets were also produced through micro-propagation. Several types of mycorrhizal fungi were used. Mycorrhizal inoculated plants had high shoot and root dry weight, greater nutrient uptake than non-mycorrhizal plantlets. Under field conditions, the effect of several mycorrhizal species on orange, mandarin and lemon trees was successfully demonstrated. Mycorrhizal inoculation also significantly increased the P and Zn uptake. Different mycorrhizal fungi differentially affected nutrient uptake and this effect depended upon the species. Mycorrhizal dependency of a range of tree species was assessed. It has been found that many plants, including citrus, pistachio, cherry, banana and grapevine rootstocks are dependent on mycorrhizae for P nutrition. Overall, it is concluded that utilizing AM fungi can make a useful contribution to horticultural plant growth, nutrient uptake and also fruit quality. © 2018 International Society for Horticultural Science. All rights reserved