Research Article Plant Growth-Promoting Rhizobacteria Enhance Salinity Stress Tolerance in Okra through ROS-Scavenging Enzymes Sheikh Hasna Habib, 1,2 Hossain Kausar, 3,4 and Halimi Mohd Saud 1 1 Department of Agricultural Technology, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia 2 Oilseed Research Centre, Bangladesh Agricultural Research Institute (BARI), Gazipur 1701, Bangladesh 3 Laboratory of Food Crops, Institute of Tropical Agriculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia 4 Department of Agroforestry and Environmental Science, Sher-E-Bangla Agricultural University, Dhaka, Bangladesh Correspondence should be addressed to Halimi Mohd Saud; halimi@upm.edu.my Received 10 September 2015; Revised 29 December 2015; Accepted 30 December 2015 Academic Editor: Qaisar Mahmood Copyright © 2016 Sheikh Hasna Habib et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Salinity is a major environmental stress that limits crop production worldwide. In this study, we characterized plant growth- promoting rhizobacteria (PGPR) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase and examined their efect on salinity stress tolerance in okra through the induction of ROS-scavenging enzyme activity. PGPR inoculated okra plants exhibited higher germination percentage, growth parameters, and chlorophyll content than control plants. Increased antioxidant enzyme activities (SOD, APX, and CAT) and upregulation of ROS pathway genes (CAT, APX, GR, and DHAR) were observed in PGPR inoculated okra plants under salinity stress. With some exceptions, inoculation with Enterobacter sp. UPMR18 had a signifcant infuence on all tested parameters under salt stress, as compared to other treatments. Tus, the ACC deaminase-containing PGPR isolate Enterobacter sp. UPMR18 could be an efective bioresource for enhancing salt tolerance and growth of okra plants under salinity stress. 1. Introduction Soil salinity is a major problem in agriculture that limits plant growth and causes signifcant loss of crop productivity worldwide [1, 2]. Salinity afects up to 20% and 50% of the total cultivated and irrigated land in the world, respectively [3]. However, the use of saline water in agriculture is gradually increasing owing to shortage of fresh water. Consequently, on one hand, salt-afected areas are constantly increasing, and, on the other hand, a signifcant amount of arable land is being abandoned every year because of salinity [4]. Okra (Abelmoschus esculentus L.) is an annual vegetable crop cultivated in tropical and subtropical regions. It is considered a high-value vegetable crop owing to its high levels of vitamins, minerals, carbohydrates, and fats [5]. Although it has good nutritional value as well as high con- sumer demand, the yield of okra per hectare is very low, and this lower productivity arises mainly from soil salinity. Salt deposits in the crop feld are a result of the use of saline underground irrigation water. Discharge of industrial efuents into irrigation canals is also a potential source of salts in agricultural soil. Saline water reduces the transpiration rate of plants by disrupting the evapotranspiration system thus reducing crop yield [6]. A high percentage of salt in the root zone afects root density, root turgor pressure, and water absorption, which eventually afects plant growth and development. Te okra plant is sensitive to salinity especially in the early stage of its growth [7] where salinity afects water and nutrient uptake of the plant, and ionic stress reduces leaf expansion. Altered morphological traits in the canola plant [8], reduced plant dry matter and leaf area in soybeans [9], and reduced yield of canola [10] due to salinity have been reported. In the root zone, high salt concentration decreases soil water potential and water availability, which causes dehydration at the cellular level, eventually leading to osmotic stress [11]. Hindawi Publishing Corporation BioMed Research International Volume 2016, Article ID 6284547, 10 pages http://dx.doi.org/10.1155/2016/6284547