Salinity stress and some physiological relationships in Kochia (Kochia scoparia)

Introduction Soil salinity is one of the major abiotic stresses affecting plant growth and production. It is estimated that approximately half of the irrigated lands of Iran are affected by salinity and much of the agricultural lands of Iran especially in the central regions are susceptible to salinity. According to the development of saline soils and water resources, utilization of halophytes as alternatives for cultivation in saline conditions could be a suitable strategy to crop production. In addition to understanding the physiological salinity tolerance pathways, studying such crops could help to plant breeding and transferring these useful traits to crop species and also domestication of these plants. Materials and methods This experiment was conducted in 2009-2010 in Salinity Research Station of faculty of agriculture, Ferdowsi University of Mashhad as split-plot based on Complete Randomized Block Design with three replications. Salinity as the main plot had two levels of 5.2 and 16.5 dSm-1 and five kochia ecotypes including Birjand, Urmia, Borujerd, Esfahan and Sabzevar were allocated as sub-plot. Seedlings were irrigated with saline water having electrical conductivity (EC) of 5.2 dSm-1 until the full establishment and thereafter salinity stress was imposed with saline water having EC=16.5 dSm-1. Physiological and biochemical traits were measured in the youngest fully expanded leaf at the beginning of the anthesis and shoot biomass at the end of the growth season. Data analysis was performed using Minitab 16 and means were compared by LSD test at a significance level of 0.05. Results and Discussion Results indicated that biomass was increased in Birjand, Isfahan and Urmia ecotypes as salinity level increased while it was decreased in Sabzevar and Boroujerd ecotypes. A reduction of 34, 31, 11 and 29 percentage and an increase of 4 percentage in seed yield was seen in Sabzevar, Birjand, Boroujerd, Urmia and Isfahan, respectively. Harvest index was also increased in Isfahan while it was decreased in the other ecotypes with the highest reduction in Birjand ecotype. An increasing trend of shoot Na+ content at anthesis was observed in all ecotypes showing the highest increase in Boroujerd and Isfahan and the lowest in Birjand ecotypes. A lower shoot K+ content at anthesis was observed in all ecotypes except Urmia in higher salinity levels. In contrast to Sabzevar soluble carbohydrates was decreased in Urmia, Isfahan, Boroujerd and Birjand in higher salinity levels. Increasing salinity intensity caused an increase in leaf proline content in Birjand and Isfahan ecotypes while it had no effect on Boroujerd and an additive effect on this parameter in Urmia and Sabzevar ecotypes. A higher osmotic potential was found in Boroujerd, Birjand and Sabzevar in higher EC levels. Phenol content was lower in Urmia, Boroujerd and Birjand in higher salinity levels while it was higher in Sabzevar. No significant difference was observed in Isfahan ecotype according to this parameter. DPPH radical scavenging activity was decreased in Birjand, Urmia and Boroujerd while it was increased in the other two ecotypes. Conclusion Regarding higher biomass and lower physiological indices such as soluble carbyhydrates, total phenol, DPPH radical scavenging activities in Birjand and Urmia ecotypes, it may be cocluded that higher amounts of these parameters might not be suitable traits in salinity tolerant genotypes selection.