The International Journal of Engineering and Science (IJES) || Volume || 7 || Issue || 9 Ver.I || Pages || PP 54-58 || 2018 || ISSN (e): 2319 – 1813 ISSN (p): 23-19 – 1805 DOI:10.9790/1813-0709015458 www.theijes.com Page 54 Improvement of Abiotic Stress Tolerance in Onion: Selection Studies Under Salinity Conditions Fatih Hanci, Esra Cebeci Erciyes University, Faculty of Agriculture, Department of Horticulture, 38280, Kayseri, Turkey Bati Akdeniz Agricultural Research Institute, Antalya, Turkey Corresponding Author: Fatih Hanci --------------------------------------------------------ABSTRACT---------------------------------------------------------------- Onion (Allium cepa L.) is one of the most important vegetable in Turkey, and often cultivated in arid and semiarid regions with salinity problems. In the first year of the study, three onion varieties were evaluated at various levels of salinity to identify susceptibility and tolerance levels. At the end of the experiment, “Akgun” determined more tolerant than the other varieties. At 9.6 dSm -1 condition, the survived individuals of this variety were selected as “candidate line”. Selected individuals were grown to maturity and self-pollinated to produce next generations. In the third year of the study, the plants have been grown in vermiculite by substrate culture technique. The early plant stage at the 250 mM NaCl was used for the second selection studies. The same selection procedures were repeated once more on the next season. At each selection stage, the individuals were selected based on plant mortality. At the last year of study, the selected line was evaluated for both seed germination and seedlings growth at three treatment levels of 0 (nonstress), 250 mM, and 350 mM NaCl and were compared with the unselected population. The results indicated that selections were effective at all two salt-stress levels. KEYWORDS: Allium, Salinity, Selection, Variation --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 25-08-2018 Date of acceptance: 08-09-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION The saline conditions have numerous intensive effects on plant growth because of a low particular ion effect, osmotic potential of the soil solution, nutritional instabilities, or a combination of these factors [1;2]. According to the predictions of the scientists, around 50% of the current planted land for cultivation might be lost by 2050 if the present scenario of salinity stress would continue [3]. In addition to this, worldwide yearly losses in agricultural output from salt-affected lands are in excess of US$12 billion and rising [4]. Developing varieties able to maintain productive at low to moderate levels of salt stress by breeding studies may provide a relatively cost-effective short-term solution to this issue [5]. The determination of varieties as tolerant or sensitive would be an influential strategy to accomplish the salinity stress. According to the behavior in saline environments, plants can be classed as glycophytes (salt susceptible) halophytes (salt tolerant) [6;7]. Many glycophytes are incapable to transcribe osmotically under salt stress. In contrast, halophytes generally sustain high turgor potential by the accumulation of ions [6]. According to Flowers and Yeo (1995), five methods can be suggested to develop salt-tolerant varieties: (1) develop new crops from halophytes, (2) interspecific hybridization between current crops, (3) utilization of the variation already present in available crops, (4) create variation within present crops by using repeated selection, mutagenesis or tissue culture, (5) developing new varieties for high yield rather than salt tolerance [8]. Strategies for breeding for salt tolerance were described long ago for in both cross-pollinating and self-pollinating species by Dewey (1962) and Ramage (1980) [9;10]. Onion (A. cepa L.) has a big importance in agricultural production in over the entire world. Vavilov (1926) reported that the main center of domestication and diversity is Southwest Asia. In addition, the Mediterranean region is defined as the secondary center of origin for onions with large bulbs [11;12]. In 2016, 93 million tons of onions were harvested from 4.96 million hectares area worldwide. The Turkeys’ onion production quantities were 2.12 million tons in the same year [13]. Onion is classified as salt-sensitive with 1.2 dS·m−1 electrical conductivity (EC) threshold [14;15]. A lot of reports have been published about on influence of salinity on germination capability, growth parameters, yield attributes, and flavor in this crop [16;17;18;19;20;21]. The present study was designed with the aims of the selection of onion genotypes for moderate salinity stress tolerance. For this aim, the effectiveness of repeated phenotypic selection was investigated.