Effect of deficit irrigation on agronomic, technological and physiological properties of Istanbul oregano (Origanum vulgare subsp. hirtum) (Link) Iestwaart populations and determination of drought-resistant genotypes and associating them with marker-assisted selection

Objective: In this study, effects of deficit irrigation on agronomic, technological and physiological responses of different genotypes of Istanbul oregano (Origanum vulgare subsp. hirtum) were investigated also it was aimed to determine tolerant genotypes for drought. 12 genotypes were selected as tolerant, alternative and sensitive according to preliminary study that conducted with 140 different genotypes in the greenhouse. The success of the study carried out in the greenhouse was investigated by comparing it with the field study. Connections between primers and drought resistance were investigated by comparing the results of 9 EST-SSR primers with field and laboratory studies on 12 selected genotypes. Material and Methods: Origanum vulgare subsp. hirtum species (A, B, C, D and E) populations were selected on field conditions from high-yield A and B clones. In the study, a preliminary study was carried out using Polyethylene Glycol 6000 (PEG 6000) in greenhouse conditions with 140 genotypes in order to establish a field study from clones of Istanbul oregano populations. The field study was conducted with 12 different genotypes which selected from the preliminary study that conducted in the greenhouse. The field study take place in the Medicinal Plants fields of Aydın Adnan Menderes University, Faculty of Agriculture, Department of Field Crops for three years in 2018-19, 2019-20 and 2020-21. It was conducted with 4 replications according to split plots design, and aplications were formed with 12 different genotypes and irrigation levels (33%, 67% and 100% of soil capacity). In the study, a dendogram was drawn by combining the agronomic and technological data together with the results of the analysis on 12 different genotypes using 9 EST-SSR primers, also similarities between the genotypes were examined. Results: Plant height 51,8-70,8 cm, fresh herb yield 521,1-1539,3 kg/da, drug herb ratio 31,3-47,8%, drug herb yield 203,2–701,5 kg/da, drug leaf ratio 47,7-66,8%, drug leaf yield 109,62-390,65 kg/da, stem yield 87,1-310,8 kg/ha, stem ratio 33,2- 52,3%, dry matter yield 189,38-585,93 kg/da, relative humidity 55,9-67,5%, SPAD 25,0-60,3, essential oil ratio 4,6-8,8%, essential oil yield 5,5-33,4 l/da, FRAP 47,8-84,6%, DPPH 24,6-75,9%, flavonoid 77,1-182,4 mg Rutin/g and carvacrol was found as 59,9-94,0%. It was determined that while plant height, fresh herb yield, dry matter yield and stem yield decreased in 2020 with deficit irrigation conditions. However, it was determined that there was an increase in all technological properties (essential oil ratio, essential oil yield, antioxidant, antiradical and flavonoid) with deficit irrigation. In 2021 while some of the agronomic parameters were decreased in 100% irrigated dose, it was revealed that there was an increase in technological parameters at 33% irrigation dose, as previous year. According to the dendogram graph, tolerant and sensitive genotypes were formed different groups. Conclusion: Since Istanbul oregano is a plant used as an essential oil plant, it can be used easily in regions with limited water conditions. In this respect, it is a plant with a future in our country where water resources are insufficient. Preliminary greenhouse study were found to be compatible with the results of field and laboratory studies, except for the genotype C-548. In this case, it can be said that the preliminary greenhouse study was successful and the genotype C-548 showed different characteristics in field conditions. In addition, it was determined that genotypes A-210, B-575, C-290, C-425, E-11 and E-302 could be used in limited irrigation conditions. As a result of molecular study, it was determined that OR9, OR10, OR12, OR40 and OR44 primers were more successful than other primers in separating genotypes. Keywords: Origanum vulgare subsp. hirtum, Polyethylene glycol, Essential oil, Drought, Molecular genetics