Protocol for Screening for Salt Tolerance in Barley and Wheat
A simple protocol is presented that tests salt tolerance in wheat and barley seedlings. The method is based on a glasshouse, aerated hydroponics test in which salt is added to the nutrient hydroponic solution in which the seedlings are grown. A list of equipment is provided including hydroponic hardware and stock solutions. Advice is given on seed storage prior to use and pregermination treatments that promote even germination of test samples. Salt treatments commence after seedling establishment in hydroponics at the 2–3-leaf stage. Visual symptoms of salinity stress include reduced leaf area, whitish appearance of lower leaves, leaf tip death, leaf rolling and seedling death. Recommended test salt concentrations for testing wheat and barley are given along with a method of recovering selected plants. Examples of protocol used are also given.
KeywordsSodium Hypochlorite Hydroponic System Hydroponic Solution Ring Tube Feeder Tube
The protocol for rice needs to be adapted for other cereals such as wheat and barley. Changes are required for germination, aeration of hydroponics and test concentration. Wheat and barley seeds do not germinate well when submerged and therefore cannot be germinated in the hydroponics platforms. Seeds are therefore pregerminated and young seedlings are transferred to hydroponics. Also, wheat and barley cannot tolerate anaerobic growing conditions, and their roots need to be aerated in hydroponics. Moreover, wheat and barley are more tolerant to salt than rice and therefore are tested at higher concentrations.
5.2 Adaptations of Rice Protocol to Wheat and Barley
5.2.2 Hydroponic Solution
Composition of Hoagland’s solution
Seedlings are grown on to the two-leaf stage and should appear green and healthy prior to testing.
Ring tube: internal diameter 25 mm
Feeder tube: internal diameter 0.6 mm
Aeration rod: internal diameter 0.6 mm
5.2.4 Glasshouse Conditions
The test is normally carried out in a glasshouse set-up for temperate crops: 20/15 °C (day/night) with a 16 h photoperiod.
Aeration rods can be made from 0.6 mm steel tubing cut to length with one end sealed by clamping.
With this system, 6–10 hydroponic tanks can be accommodated on a bench of 2 × 1 m (Fig. 5.3c, d).
As soon as seedlings go into hydroponics, they are aerated.
5.2.5 Test Salt Concentrations
Plants differ greatly in their tolerance of salinity. Wheat and barley are more tolerant to salinity than rice. Therefore, different salt concentrations are used. Typical concentrations used for screening wheat and barley are 15–20 dS m−1 or 150–200 mmol NaCl, compared to 10 dS m−1 or 100 mmol NaCl for rice.
Salt treatments are applied to seedlings established in hydroponics (two-leaf stage in Hoagland's solution). This is done by transferring the platform of seedlings from control tanks to hydroponic tanks containing the test NaCl concentration in Yoshida solution. This is a one-step method. An alternative is to add salt in daily increments of 25 mmol until the test concentration is reached (this will reduce the effect of osmotic shock).
- Hoagland DR, Arnon DI (1950) The water culture method for growing plants without soil. College Agriculture circular No. 347, College of Agriculture, University of California, BerkeleyGoogle Scholar