Evaluation the freezing tolerance of wild barley (Hordeum spontaneum Koch.) and feral rye (Secale cereale L.) compared to wheat (Triticum aestivum L.) at the two-leaf stage

In temperate regions such as Iran, freezing stress tolerance is one of the plants success factors in autumn planting. So, evaluation the crops and their common weeds tolerance to the freezing will provide information about their competitive ability in these conditions, and appropriate information on weeds management. For this purpose, a greenhouse experiment was conducted in autumn 2017 in Faculty of Agriculture, Ferdowsi University of Mashhad. Wheat (Pishgam cultivar and Ghezel khoushe landrace) and wild barley and feral rye weeds were grown up to the two leaves stage in natural conditions and then, were exposed to cold and freezing temperatures (+4, 0, -4, -8, -12, -16 and -20oC). Results showed that the percentage of electrolyte leakage began to increase by temperature reduction from -8°C to -20°C and reached to its maximum. While all plants maintained their 100% survival to -12°C, wild barley had a 36% reduction in survival at this temperature. The higher LT50su in wild barley and therefore the faster survival reduction confirmed its more sensitivity to freezing temperature than other plants. At -12 °C, wild barley dry weight had higher dry weight reduction declined compared to other plants that due to high RDMT50, this plant showed more sensitivity to freezing temperatures while feral rye and Pishgam cultivar and wheat Ghezel khoushe landrace of wheat had less RDMT50, indicating the high competitive ability of feral rye in freezing conditions. There was negative and significant correlation between electrolyte leakage and survival percentage and also survival percentage and LT50su (r= -0.93* and r=-0.99** respectively). Therefore, according to the results of the present experiment, weed management priority in cold climate areas is feral rye.