565 Influence of Mycorrhizae in Geranium Irrigated with Saline Water: Agronomic and Environmental Responses A. Navarro and M. Mastrorilli A. Elia and G. Conversa Agricultural Research Council University of Foggia Research Unit for Cropping Systems in Department of Agro- Environmental Dry Environments Science, Chemistry and Plant Protection Bari Foggia Italy Italy Keywords: Pelargonium × hortorum, AM fungi, salinity, chemical composition, growth parameters, leaching Abstract No information seems to be available on the effect of mycorrhizae on reducing the environmental impact of saline-water irrigation. This study investigated 1) the behaviour of mycorrhizal and non-mycorrhizal geranium plants irrigated with saline water; and 2) the influence of the symbiosis on the leachates and the substratum. Mycorrhizal (Glomus deserticola and Glomus intraradices) and non-mycorrhizal plants of Pelargonium × hortorum ‘Markab’ were grown in pots for three months in a greenhouse and subjected to three irrigation treatments. Each treatment represented an EC salinity level (0.85 dS m -1 , control, C; 3 dS m -1 , medium salinity, MS; 6 dS m -1 , high salinity, HS). The frequency and intensity of mycorrhizal colonization by G. intraradices in geranium roots was greater than colonization by G. deserticola. For increasing salinity levels, ionic uptake in geranium plants (Cl - , Na + and Ca 2+ ) was greater and accordingly, ionic concentrations (Cl - , Na + , Ca 2+ but also K + ) were higher in the leached water. The chemical composition of the substratum was significantly modified by salinity. Mycorrhizae increased leaf area and dry shoot weight and the Cl - , Na + and Ca 2+ concentrations found in mycorrhizal plants were smaller than in non-mycorrhizal plants. A decrease in Cl - and Na + concentration was observed in MS geraniums inoculated with G. deserticola, while G. intraradices reduced Ca 2+ and Cl - in HS plants. In leachates, the impact of salinity was mitigated by mycorrhizae, mainly G. intraradices and in the substratum, G. deserticola reduced Na + concentration in the HS treatment and total limestone in the MS treatment. Based on these results, mycorrhizal inoculation improves the growth of geranium plants under saline conditions and reduces harmful environmental effects caused by salinity. INTRODUCTION It is well known that the quantity and quality of irrigation water is an important issue for floriculture in regions with a hot-arid climates. For this reason, the agronomic and environmental consequences should be considered when irrigation involves the use of low quality water (i.e. saline water). Geranium is a species well adapted to Mediterranean climatic conditions. In this sense, the effects of water stress on growth, water relations and gas exchange have been studied previously (Montero et al., 2001; Sánchez-Blanco et al., 2009), but those related to salt stress have received very little attention. Mycorrhizae have been shown to protect crops from pathogen attacks, to increase photosynthesis and to improve the water status of plants. Nevertheless, the mycorrhizal symbiosis in geranium plants is poorly characterized, especially in relation to the ability of mycorrhizal fungi to alleviate the negative effects of salinity in irrigation water. The objective of this study was to determine the effects of different salinity concentrations of irrigation water on mycorrhizal and non-mycorrhizal geranium plants, studying growth and nutritional content of the plants and environmental responses via analyses of the quality of the substratum and leaching solutions. Proc. 6 th IS on Irrigation of Hort. Crops Eds.: S. Ortega-Farias and G. Selles Acta Hort. 889, ISHS 2011