Research in Plant Biology, 2(6): 23-29, 2012 ISSN : 2231-5101 www.resplantbiol.com Received: 5.10.2012; Revised: 28.11.2012; Accepted: 30.11.2012 Regular Article In vitro evaluation of iron-deficiency tolerance in an endemic putative apple rootstock Hassan Mahdavikia and Nasser Mahna * Departmen of Horticultural Sciences, Faculty of Agriculture, University of Tabriz, 51666- 16471, Tabriz, Iran * Corresponding author: mahna@tabrizu.ac.ir & n.mahna@gmail.com In most species of fruit trees, iron deficiency-induced chlorosis causes several economic damages. Recently, in vitro culture techniques have been used to assess rootstocks for susceptibility to iron deficiency-induced chlorosis. In the present study, the in vitro shoots of three apple genotypes including Malus baccata, MM.106 and Gami- Almasi, a native putative apple rootstock, were evaluated on MS medium supplemented with four concentrations of Fe (0, 9, 18, 36 mg/L) from Fe-NaEDTA and the concentration of Fe in MS medium as the control. Visual chlorosis index, leaf chlorophyll index, leaf area, fresh weight increment and dry weight of shoots were determined 26 days after culture. Iron concentrations affected the visual chlorosis index of M. baccata and MM.106. However, there were no chlorosis symptoms in Gami-Almasi. Leaf chlorophyll index were affected significantly by genotypes and Fe concentration. Leaf area and fresh weight increment differed significantly in various genotypes; nevertheless, the effect of Fe concentration was not significant. Leaf area and fresh weight were recorded the highest in M. baccata compared to the other two genotypes. Genotypes and Fe concentration treatments were not affected dry weight of the shoots. Keywords: apple rootstocks, in vitro evaluation, iron deficiency. Chlorotic reaction of plants to iron deficiency is a common nutritional disorder and a major contributing factor in reducing production level and horticultural products quality (Tagliavini et al, 2000). This nutritional disorder occurs frequently in calcareous soils and often results in appearance of chlorosis (Marschner & Romheld, 1994). Most of leaf iron content has been found in chloroplasts (about 80%), about 60 percent of which is stored in thylakoid membrane (Terry and Abadia 1986). Therefore, iron deficiency affects chloroplast structure and activity at first, because of the iron-dependent enzymes being mostly inactivated or damaged (Soldatini et al. 2000). For example, antioxidant enzymes such as talase C (CAT), Peroxidase (POX) and one of Superoxide dismutase (SOD) isoforms require iron in their active sites. These enzymes inactivate the reactive oxygen species (ROS) which could bind to DNA, protein and membrane lipid and lead to mutation, reduction of photosynthesis, senescence and finally death (Scandalios 1990). Perennials, especially fruit trees, when planted in alkaline and calcareous soils, normally demonstrate iron deficiency symptoms (Romera et al. 1991). Such conditions could result in diminished production level, fruit quality, and