Aluminium toxicity tolerance in cereals: Mechanisms, genetic control and breeding methods

Abstract

Aluminium (Al) toxicity is one of the major factors constraining crop production on 67% of the total acid soil area in the world. Al toxicity restricts root growth and affects nutrient and water absorption with resultant stunted growth and reduced grain and biomass yield of crops. Cereals occupy about half of the world’s cropland area and, therefore, take the lion share of the global Al-toxicity constraint. Al-toxicity is more serious in tropical environments where the soil is highly resistant to improvement by lime application. In addition, in these environments, the use of adequate lime and organic fertilizer sources is constrained by various technological and socio-economic constraints. Development and use of Al-tolerant crop varieties is economically feasible and an environmentally friendly management option that can complement other non-genetic management options. This paper introduces the importance of soil acidity and development of Al-toxicity. It also summarizes limitations of non-genetic management options and the need to complement these approaches with tolerant varieties. Further account is given on the effects of Al-toxicity on plant growth and development and yield. Organic acid exudation and other tolerance mechanisms of the globally important cereals and their genetic control are also discussed in details. The authors believe that the screening methods outlined in this review provide basic information and insights about Al-tolerance breeding in cereal crops.   Key words: Al-tolerance, genetic control, cereals, Al-toxicity.