Abstract
BackgroundAluminum (Al) toxicity is a major worldwide constraint to crop productivity on acidic soils. Al becomes soluble at low pH, inhibiting root growth and severely reducing yields. Maize is an important staple food and commodity crop in acidic soil regions, especially in South America and Africa where these soils are very common. Al exclusion and intracellular tolerance have been suggested as two important mechanisms for Al tolerance in maize, but little is known about the underlying genetics.MethodologyAn association panel of 282 diverse maize inbred lines and three F2 linkage populations with approximately 200 individuals each were used to study genetic variation in this complex trait. Al tolerance was measured as net root growth in nutrient solution under Al stress, which exhibited a wide range of variation between lines. Comparative and physiological genomics-based approaches were used to select 21 candidate genes for evaluation by association analysis.ConclusionsSix candidate genes had significant results from association analysis, but only four were confirmed by linkage analysis as putatively contributing to Al tolerance: Zea mays AltSB like (ZmASL), Zea mays aluminum-activated malate transporter2 (ALMT2), S-adenosyl-L-homocysteinase (SAHH), and Malic Enzyme (ME). These four candidate genes are high priority subjects for follow-up biochemical and physiological studies on the mechanisms of Al tolerance in maize. Immediately, elite haplotype-specific molecular markers can be developed for these four genes and used for efficient marker-assisted selection of superior alleles in Al tolerance maize breeding programs.
Highlights
Aluminum (Al) toxicity from acidic soil is a major constraint to worldwide crop production
Elite haplotype-specific molecular markers can be developed for these four genes and used for efficient marker-assisted selection of superior alleles in Al tolerance maize breeding programs
Phenotypic data Phenotypic data for Al tolerance in the maize association panel was collected as net root growth (NRG) in a hydroponic nutrient solution with or without a toxic level of Al3+ [37]
Summary
Aluminum (Al) toxicity from acidic soil is a major constraint to worldwide crop production. One of the most abundant elements in the soil, is solubilized as Al3+ under acidic soil conditions This form of Al is highly toxic to plant roots. Soil amelioration with compounds such as lime can be used to temporarily neutralize the topsoil This is not a feasible option for resource poor farmers or for subsoil acidity, and is not an economically or agronomically sustainable solution. Investing in the production of Al tolerant maize varieties and alternative management practices can contribute greatly to increased yield and sustainable crop production from acidic soils [5,6]. Maize is an important staple food and commodity crop in acidic soil regions, especially in South America and Africa where these soils are very common. Al exclusion and intracellular tolerance have been suggested as two important mechanisms for Al tolerance in maize, but little is known about the underlying genetics
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