The effects of JA treatment on the growth and some enzyme activities of eggplant embryos grown in vitro under salt stress conditions

In many areas of the world, soil salinization is an important concern for the sustainability of irrigated agriculture and accounts for large decreases in the yield of a wide variety of crops. Numerous attempts have been employed to optimize plant growth under saline conditions. One of them is to produce salt tolerant genotypes in different crops by traditional breeding. In addition, many other attempts have been made to overcome this disorder by exogenous application of plant growth regulators. Plant hormones are active members of the signal compounds involved in the induction of plant stress responses. Jasmonic acid (JA), which is naturally synthesized by plants, plays an important role as a signal molecule that induces the tolerance mechanisms under the influence of both biotic and abiotic stresses. In this study we aimed to investigate the effects of JA individually and/or accompanied with salt stress on two cultivars of eggplant embryos cultured in vitro. Embryos gently isolated from the 32-days old eggplant seeds and then were transplanted onto hormone-free MS medium basically containing 2% saccharose, 0.7% agar at pH 5.7. Different concentrations of NaCl and JA were applied with nine different applications. Two cultivars of eggplant were used: cv. Mardin Kiziltepe (M: Tolerant) and cv. Kemer (K: Sensitive). Germination percentage and antioxidative enzymes, SOD, CAT and APX activities were determined after harvesting. Among all applications of JA, plantlets that were pre-treated with 10 mu M JA and then transferred to the salty media showed relatively better development than the other applications. Germination rate was 100% and plant growth was normal in control application. However germination rate and plant growth were inhibited by salt or JA application. The addition of JA caused more inhibition than salt stress. Among all applications of JA, embryos that were pre-treated with JA (cultured on the medium with 10 mu M JA for 4 days and then transferred to the growth media with salt) showed relatively better development than the others. Antioxidative enzyme (SOD, CAT and APX) activities, increased with salt or JA treatments compared to control plants. The SOD, CAT and APX activities of the salt-tolerant Mardin Kiziltepe genotype were higher than salt-sensitive Kemer variety.