Aluminum-TolerantPisolithusEctomycorrhizas Confer Increased Growth, Mineral Nutrition, and Metal Tolerance toEucalyptusin Acidic Mine Spoil

Abstract

Ectomycorrhizal fungi (ECM) may increase the tolerance of their host plants to Al toxicity by immobilizing Al in fungal tissues and/or improving plant mineral nutrition. Although these benefits have been demonstrated inin vitro(pure culture) or short-term nutrient solution (hydroponic) experiments, fewer studies have examined these benefits in the field. This study examined the growth, mineral nutrition, and Al levels in twoEucalyptusspecies inoculated with threePisolithusecotypes that varied in Al tolerance (in vitro) and grown in mine spoil in the greenhouse and field. All three ecotypes ofPisolithusimprovedEucalyptusgrowth and increased host plant tolerance to Al in comparison to noninoculated plants. However, large variations in plant growth and mineral nutrition were detected among thePisolithus-inoculated plants; these differences were largely explained by the functional properties of thePisolithusinoculum. Seedlings inoculated with the most Al-tolerantPisolithusinoculum showed significantly higher levels of N, P, Ca, Mg, and K and lower levels of Al than seedlings inoculated with Al-sensitive ecotypes ofPisolithus. These findings indicate an agreement between the fungal tolerance to Alin vitroand performance in symbiosis, indicating that both ECM-mediated mineral nutrient acquisition and Al accumulation are important in increasing the host plant Al tolerance.