Journal of Applied Botany and Food Quality 87, 182 - 189 (2014), DOI:10.5073/JABFQ.2014.087.026 Department of Horticulture, Faculty of Agriculture, Shiraz University, Shiraz, Iran Effect of 24-epibrassinolide on salinity-induced changes in loquat (Eriobotrya japonica Lindl) Fatemeh Sadeghi, Akhtar Shekafandeh* (Received October 30, 2013) * Corresponding author Summery This study was carried out to investigate the role of 24-epibrassinolide (24-EBL) in inducing loquat plant salt tolerance. Plants were treated with ive levels of salt, so that the electrical conductivity (EC) of 0.5 (control), 2, 4, 6 and 8 dS m -1 was established in pots. Then, the plants were sprayed with different concentrations of 24-EBL (0, 0.25, 0.5 and 0.75 mg l -1 ). Under salt stress, the plant growth parameters and chlorophyll content decreased, while the total soluble sugars and proline contents considerably increased. However, the application of 24-EBL signiicantly ameliorated the plant growth by reducing the adverse effects of salinity on the examined parameters. The ion concentrations showed an increase in accumulation of Na + and Cl - coupled with a decrease in K + with increasing salinity in medium. Exogenous application of 24-EBL had a signiicant effect on leaf Na + , K + , Cl - contents. Out of different 24-EBL concentrations, the effects of 0.5 mg l -1 proved the best under stress conditions. Introduction Loquat (Eriobotrya japonica Lindl.) is a subtropical evergreen fruit tree of Rosaceae family, (Lin et al., 2007; Zheng, 2007) which is grown commercially in subtropical to mild temperate climate. Loquat is commonly propagated by seed; as a result, the plants possess variable performance and different fruit characteristics owing to heterozygosis and cross-pollination. Therefore, in some parts of the world, the seedlings employ as a rootstock for cultivars with high fruit quality (Lin, 2007). Salinity is one of the major abiotic stresses that affects plant production and growth in many arid and semi-arid areas throughout the world (CheLLi-Chaabouni et al., 2010). Iran is now faced with salinity problems in about 34 % of its area in addition to harsh conditions of climate in about half of the country. This also signals that global climate change and consecutive years of drought is likely to increase salinity of the main agricultural lands (Rahimian et al. 2013). The deleterious effects of salinity on plant growth are associated with low osmotic potential (water stress), nutritional imbalance, speciic ion effect (salt stress), or a combination of these factors. All these factors cause adverse effects on plant growth and development at physiological and biochemical and molecular level (ashRaf and haRRis, 2004). Among the most common effects of salinity is growth inhibition by NaCl. In many plants, compatible osmoprotectant metabolites, such as proline, glycine-betaine, and soluble sugars are produced to protect the cells against the damaging effects from salt stress (CheLLi-Chaabouni et al., 2010). Although, soil salinity directly affects root system, hence breeding and selection of salt tolerant rootstock for sustainable fruit produc- tion is inevitable, but this is a time consuming. For reducing adverse effects of salinity different strategies have also been developed. One of these approaches is; employing different types of phytohormones (houimLi et al., 2008). Among them, Brassinosteroids, a recent class of plant hormone not only play prominent role in various physio- logical and biochemical processes in plants, like stem elongation, vascular differentiation, leaf bending and epinasty, induction of ethylene biosynthesis, regulation of gene expression, nucleic acid and protein synthesis and photosynthesis (hayat et al., 2010; KRishna, 2003; yu et al., 2004; Cao et al., 2005), but has also attracted increasing attention in studies addressing to adaptive response to environmental stresses, such as heavy metal (aLi et al., 2008; hayat et al., 2007), salt (aLi et al., 2007), temperature (WiLen et al., 1995), drought (Zhang et al., 2008). Loquat is considered as having a moderate tolerance to drought but there are some conlicting evidences on the loquat salt tolerance. Some sources have mentioned its moderate tolerance to NaCl (giLman and Watson 1993) and others its salt-sensitive (http:// aciar.gov.au/files/node/2275/mn050_part_5_pdf_19541.pdf). Knowing about salt tolerance limit of loquat helps us in extending its cultivation in area with certain levels of salinity which are not suitable for citrus. So, the present investigation was conducted to discover the salt tolerance of seedlings, effect of 24-EBL on its salt tolerance, and to determine the interactive effects of salinity and 24- EBL on plants morphophysiological characteristics. Materials and methods Plant material and treatments The loquat uniform seeds were extracted from mature fruits and immediately washed with tap water and placed at 4 ˚C for 2 weeks. Germinated seedlings were allowed to grow in perforated polyethylene pots contained a mixture of peat-moss, sand and clay (1:1:1, v/v/v). Then, when the height of the seedlings in pots was about 30 to 40 cm, the same vigour seedlings were transferred to 7 litre plastic pots illed with 6 kg soil mixture as mentioned above. The ield capacity of the soil used for potting was determined according to the protocol described by RiChaRds (1949). Potted seedlings were irrigated for 8 months to ield capacity level. In order to achieve optimum seedling vegetative growth, Fasemko complete fertilizer (pH 6.7) was applied to each pot with irrigation water each fortnight. The seedlings were grown in the greenhouse at day/night temperature: 30/25±4 °C and relative humidity of 40-45 % under natural sun light. After this period, when the seedlings were well established, a factorial experiment was conducted in completely randomized design with 4 replications. Treatments were 5 levels of salt (NaCl) × 4 levels of 24-epibrassinolide (24-EBL). The salts were applied to pots by irrigation water step-wise until an electrical conductivities (EC) of 0.5(control), 2, 4, 6 and 8 dS m -1 were attained. After that, plant were treated exogenously with 0.0, 0.25, 0.5 and 0.75 mg l -1 of 24-epibrassinolide (24-EBL) at run-off. This action was repeated 3 times with one week interval, and then six weeks after spraying, data were recorded. Growth measurements At the end of experiment, plants were harvested and divided into shoots and roots, after measuring of shoot and root fresh weight