Mycorrhizal Symbioses of Cotton Grown on Sodic Soils: A Review from an Australian Perspective

The majority of terrestrial plants form some type of mycorrhizal symbiosis. This established symbiosis therefore exists in most commercially important crops, which includes cotton. Arbuscular mycorrhizal fungus (AMF) can colonise 50%-90% of cotton root length under field and controlled conditions. Mycorrhization improves growth and nutrient uptake (especially phosphorus) of cotton, particularly at the early growth stages. Mycorrhizal symbioses help plants to counter the stresses imposed by physical and chemical soil constraints; however, adverse environmental conditions may restrict the mycorrhizal associations and consequently may reduce nutrient uptake and impair plant growth. In Australia, cotton is mainly grown on sodic soils that contain more than 6% of the total cations as exchangeable sodium. High levels of sodium in the soil create adverse physical and chemical soil conditions that may negatively affect mycorrhizal symbioses of cotton. This review discusses the cotton mycorrhizal colonisation, plant growth, and disease protection effects, potential negative effects of physical and chemical properties of sodic soils, and influences of some agronomic management practices. In addition, the research gaps were identified and some practical applications of the research outcomes were suggested.