Response of Maize (Zea mays L.) Genotypes to Soil Acidity Using Different Screening Methods in the Eastern Cape Province, South Africa

Thembalethu Mkafula, Charles Mutengwa, Simphiwe Mhlontlo, Liliane Tandzi and Azile Dumani

Background and Objective: Soil acidity is one of the major abiotic constraints to the attainment of food security in many parts of the world. This study had two main objectives which were to: (i) Identify maize genotypes with tolerance to highly acidic soils at seedling stage and (ii) Identify secondary traits associated with seedling tolerance to soil acidity. Materials and Methods: Glasshouse and laboratory experiments were established to screen ten maize genotypes for tolerance to soil acidity. Plant height, leaf area, stem diameter and dry matter were measured. The haematoxylin assay was conducted in the laboratory to determine the response of the same 10 maize genotypes to aluminium (Al) toxicity. Root staining intensity as well as shoot and root lengths was recorded 7 days after germination. The root growth stress tolerance index (RGSTI) and shoot length stress tolerance index were computed for both the glasshouse and laboratory experiments. Results: Mean square values of traits and indices recorded using the two assays revealed that it was only the RGSTI that showed significant interaction among varieties and environments and it was used to discriminate genotypes based on their response in the two assays. The RGSTI ranked four similar genotypes (Ngoyi, BG3492BT, PAN6Q408 and PHB3442) among the top 5 performers under both the laboratory and glasshouse assays. These were considered the most tolerant genotypes in this study. Conclusion: The RGSTI can therefore be a very powerful index for discriminating genotypes’ response to Al stress under laboratory and glasshouse conditions. Further field evaluation of these genotypes is recommended to ascertain their yield potential under soil acidity.

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