Study on germination and seedling growth of various ecotypes of fennel (Foeniculum vulgare Mill.) under salinity stress

Abstract

Salinity is one of the most brutal environmental factors limiting the productivity of crops and cultivation of salt-tolerant plants has been suggested as one of the strategies for reducing the effects of salinity and utilizing saline soil and water resources. This experiment was conducted in two separate experiments, one in the laboratory to study germination and the other in the greenhouse to study seedling characteristics of various fennel ecotypes (Foeniculum vulgare) in 2020. Laboratory experiment was performed in factorial base on completely randomized design with three replications and two factors. Factors included four salinity concentrations (0, 4, 8, and 12 dSm−1) and 19 fennel ecotypes (Lorestan, Kermanshah, Kashan, Damavand-Tehran, Khoramabad, Arak, Ardabil-Kalibar, Bandarabas, Ardabil, Zanjan, Tehran-Karaj, Tehran, Rodan-Hormozgan, Yazd, Shiraz, Qazvin, Khash-Sistan, Hamadan, and Isfahan). From laboratory experiment, three salt-sensitive ecotypes (Yazd, Kermanshah, and Bandarabas) and three salt-tolerant ecotypes (Isfahan, Khash-Sistan, and Rodan-Hormozgan) were identified. Greenhouse experiment was performed in factorial base on completely randomized design with three replications and two factors. Factors included four salinity concentrations (0, 4, 8, and 12 dSm−1) and six fennel ecotypes (Isfahan, Khash-Sistan, Rodan-Hormozgan, Yazd, Kermanshah, and Bandarabas). At both experiments, sodium chloride (NaCl) and calcium chloride (CaCl2) were used in two-to-one ratios to apply salinity stress treatments. The results showed that salinity decreased the mean daily germination, germination percentage, and germination rate compared with control conditions and the lowest amounts of these traits were observed at the salinity of 12 dSm−1. Salinity reduced the fresh and dry weights of roots, shoots, and total, root volume, root and shoot lengths, leaf area, relative water content, and chlorophyll content. Whereas, the amount of proline, and the ratio of sodium to potassium content of roots and shoots increased. The Khash-Sistan ecotype had the highest root fresh and dry weights, root volume, root length, and leaf area and the Bandarabbas ecotype had the lowest root fresh and dry weights, root volume, and leaf area. Also, salinity had less negative effect on traits such as relative water content and chlorophyll a, b, and a+b in the Khash-Sistan ecotype, and more negative effects on relative water content in the Bandarabas ecotype. Therefore, the Khash-Sistan ecotype was identified as a salt-tolerant ecotype and the Bandarabas ecotype was identified as a salt-sensitive ecotype.