Screening Australian turf and pasture bermudagrasses (Cynodon dactylon) for salt tolerance: association between salt tolerance and drought resistance

A large collection of over 1000 naturalised Australian bermudagrasses (Cynodon dactylon) was assembled. Previous research indicated that a subset of the grasses collected from Australian Mediterranean environments were drought resistant and characterised by large rhizomes that could be a potential source of nutrients, water and carbohydrates when these grasses grow under saline conditions. The objective of this research was to test the salinity tolerance of 12 bermudagrass genotypes with different levels of drought resistance using a flood and drain, sand-solution hydroponic system. Eight salt treatments were imposed ranging from 1.3 to 21 dS m-1 (corresponding 0 to 175 mM NaCl) for up to 17 weeks. Salinity tolerance among genotypes was categorised on the basis of 50% reduction in cumulative clipping yields, verdure and root biomass, and green cover, relative to the control treatment. There was no correlation between salt tolerance and drought resistance (r = -0.079 to 0.572), although some drought-resistant grasses did have excellent salt tolerance, such as entries MED1 and MED3. At 21 dS m-1, most grasses not only maintained over 50% total biomass but also retained over 70% green cover, relative to the control treatment, and were considered as highly salt tolerant. These salt-tolerant grasses have great potential for stabilising and revegetating saline and/or sodic soils.