Salinity affects soil, water and crop plants. The severity of soil salinity needs to be determined in order to make informed decisions on best cropping practices. Likewise, the tolerance of crop cultivars needs to be matched to the growing conditions. Protocols are therefore required to monitor field salinity and to evaluate crop tolerance to salt.
KeywordsSalt Tolerance Soil Salinity Salinity Tolerance Rice Genotype Barley Line
2.1 Monitoring Field Salinity
Soil salinity affects both, water availability and plant growth processes. Salinity refers to the presence of one or more of a number of dissolved inorganic ions (Na+, Mg2+, Ca2+, K+, SO4 2−, HCO3−, NO3− and CO3 2−) in the soil. Monitoring of soil salinity and the preparation of soil salinity maps are essential objectives for good management of salt-affected lands and the productive agriculture of salt-tolerant crop cultivars.
2.2 Screening for Salt Tolerance
The aims are to provide a screen in which salt-tolerant rice, wheat and barley lines can be selected for use in plant breeding. The screen may also be used to compare and classify salt tolerance in a range of germplasm. Extensive tests have been carried out at the IAEA’s Plant Breeding and Genetics Laboratory (PBGL) using rice genotypes with known susceptibility/tolerance to saline field conditions. Correlations have been established between seedling hydroponics responses and field salinity tolerance. Thus, the seedling screen described here can be used to select plants that may be expected to perform well in saline field conditions.
2.3 Benefits and Drawbacks of Seedling Screening
Benefits and drawbacks
• Cheap, fast and simple
• Clear classification into susceptible, moderate and tolerant types
• Tolerant seedlings may be recovered
• High-throughput screen
• Preselection technique for putative mutants
• Equipment is reusable
• Greater uniformity compared to soil-based salt tolerance screening
• Requires continual vigilance and maintenance (replenishment of test solution every 2 days)
• Solutions need to be changed; therefore, adequate stocks of chemicals are required
• Requires good-quality growing conditions
• Homogenous, good seed quality required
Seedling tests are best performed on M3 or advanced populations. Tests may be done on M2 populations which have the advantage of having relatively small population sizes, but there is a risk that the rare mutant line possessing salt tolerance is lost because of other factors, e.g. accidental miss-handling. M3 populations and above provide more rigour as there is a degree of replication for genotypes carrying the same mutant trait.