In Vitro Evaluation of Iraqi Kurdistan Tomato Accessions Under Drought Stress Conditions Using Polyethylene Glycol-6000

Drought is one of the major abiotic stresses that affect plant growth and productivity, and plant stress responses are affected by both the intensity of stress and genotype. In Iraqi Kurdistan, tomato plants play a significant role in the country's economy. Due to climate change, which causes soil moisture to diminish, the crop's growth and yield have been dropping in recent years. Accordingly, the effects of simulated drought stress on germination parameters were assessed in 64 tomato accessions gathered from the Iraqi Kurdistan region in order to identify sensitive and tolerant accessions. In this respect, the responses associated with drought stress were observed phenotypically and biochemically. Germination percentage (GP) and morphological characteristics such as root length (RL), shoot length (SL), and shoot fresh weight (SFW) were significantly reduced in both stress treatments with polyethylene glycol (PEG-6000) (7.5% PEG and 15% PEG). On the other hand, significant changes in biochemical profiles such as proline content (PC), soluble sugar content (SSC), total phenolic content (TPC), antioxidant activity (AC), guaiacol peroxidase (GPA), catalase (CAT), and lipid peroxidation (LP) in tomato accessions were detected; all biochemical traits were increased in most tomato accessions under the PEG-induced treatments compared to the control treatment (0.0% PEG). Three tomato accessions (AC61 (Raza Pashayi), AC9 (Wrdi Be Tow), and AC63 (Sandra)) were found to be the most tolerant accessions under all drought conditions, whereas the performances of the other tested accessions (AC13 (Braw), AC30 (Yadgar), and AC8 (Israili)) were inferior. The OMIC analysis identified the biomarker parameters for differentiating the highly, moderately, and low tolerant groups as PC, SSC, and TPC. This study shows that early PEG-6000 screening for drought stress may help in choosing a genotype that is suitable for growth in water-stressed environments. Hence, Raza Pashayi, Wrdi Be Tow, and Sandra accessions, which had great performances under drought conditions, can be candidates for selection in a breeding program to improve the growth of plants and production in the areas that face water limits.