Aluminium Resistance of Three Bluegrass Species.

In the world, about 40% of the total agricultural lands are acidic soils suffering low soil pH problems associated with aluminum toxicity and nutrient imbalance.  Bluegrasses (Poa spp.) are one of the major groups of cool-season grasses for forage and turf use in cool climatic zones.  Little is known about Al tolerance among bluegrass varieties.  The objective of the study was to identify degrees of Al tolerance among three commonly used bluegrasses for turf, Kentucky bluegrass, annual bluegrass, and supina bluegrass (P.  pratensis L., P. annua, Lam. and P. supina Schrad., respectively).  The study included a tissue culture  study with four levels of Al (0, 25, 50 and 100 um of Al) examining callus development and seedling root development. The tissue culture study was conducted by using callus forming media with Al for four weeks with a reduced phosphorus input. The three levels of Al were added as aluminum sulphate including the control at pH 4.0 with all other nutrients in tissue culture media. The greenhouse study was conducted with four levels of Al (0, 80, 160, and 240 um Al) under sand culture with temperature range of 25/21^oC (day/night) and a relative humidity range of 45-65%.  A 50 ml of nutrient solution with complete nutrients was added into each pot with adjusted pH 4.0 daily with/without Al as aluminum sulphate (with 10% HCl). The grasses were cultured with Al stresses for six weeks, then harvested for analyses of the total biomass and Al concentrations in shoots and roots. Annual bluegrass and supina bluegrass were more Al tolerant than Kentucky bluegrass. In all studies Kentucky bluegrass had 15-25% less biomass than annual or supina bluegrass.  Aluminum concentrations in sand culture greater than 240 um limited survival of all three bluegrass varieties.