Screening various ryegrass cultivars for salt stress tolerance

Various ryegrass (Lolium perenne L.) cultivars [Covet, OSC 129 (Covet II), Galileo, OSC 127 (Galileo II), Michelangelo, Newton, Whitney and OSC 126 (Whitney 11)] were studied in a greenhouse to evaluate their growth responses in terms of shoot and root lengths, shoot (clippings) fresh and dry matter (DM) weights and grass general quality under salinity stress conditions. Grasses were grown hydroponically using Hoagland solution No. 1. Treatments included control and sodium chloride (NaCl) at various EC levels (2,4, 6, 8, 10, 12, 14 and 16 dSm(-1)). The 8 ryegrass cultivars were grown with 4 replications of each salinity treatment in a Randomized Complete Block (RCB) design trial. Shoot and root lengths and shoot (clippings) fresh and DM weights were determined weekly. After the fresh weight determination, shoots were oven-dried at 60 degrees C and DM weights recorded. At the last harvest, roots were also harvested and fresh weights were determined, then oven-dried at 60 degrees C and DM weights were recorded. Grass general quality was daily evaluated at each stress level (one week growth period at each stress level). The results show shoot and root lengths and shoot (clippings) fresh and DM weights of all the cultivars decreased linearly with increased salinity levels. However, at each salinity level, there were only some numerical differences found in the shoot (clippings) lengths or fresh and DM weights of the various cultivars. In contrast, for all the cultivars, under any level of salinity, the root length was more severely affected than the shoot length. There were significant differences in root lengths or fresh and DM weights of various cultivars at each level of salinity. Grass general quality followed the same pattern (decreased) as the shoot (clippings) lengths, fresh and DM weights. The canopy color of all the cultivars turned to lighter green at the higher levels (EC >6 dS/m) of salinity Based on the results of this study, all the cultivars exhibited a high level of salinity tolerance.