Growth Response and Dry Matter Partitioning of Quality Protein Maize (Zea mays L.) Genotypes under Aluminum Toxicity

Abstract

In this work, 75 quality protein maize (QPM) inbred lines were evaluated for aluminum tolerance using a nutrient solution assay in a laboratory and a soil-based technique in a greenhouse tunnel. The experiment was set up in a completely randomized design with three replications in the laboratory, and a randomized complete block design was used in the greenhouse. Aluminum toxicity was generated by amending a nutrient solution with 600 µM of aluminum sulfate (Al2 [SO4]3) in the laboratory, and Al2 [SO4]3 was applied at a rate of 24 mg kg−1 of soil in the greenhouse experiment. Relative root length (RRL) and hematoxylin staining (HS) scores were used to identify tolerant genotypes in the laboratory. According to RRL, 94.7% of genotypes were tolerant and 5.3% were sensitive, while Hematoxylin (HS) classified 77.9% of the genotypes as tolerant, and 22.1% as sensitive. RRL and HS presented a very strong negative association (−0.788). In the soil-based method, the experiments were conducted twice in successive summer seasons of 2019 and 2020. Several growth traits were measured and most genotypes that exhibited tolerance in the nutrient solution also had similar tolerance in the soil-based screening technique. Genetic variability for tolerance was identified, revealing potentially useful donors of tolerance genes in breeding programs.

Dry Matter Yield Stability Analysis of Maize Genotypes Grown in Al Toxic and Optimum Controlled Environments

“…The experiment was laid out in a randomized complete block design (RCBD) with three replications in three blocks. The experimental procedure was adopted from [ 14 ] where alluvial soils, which were classified as Haplic Cambisol in accordance with the World Reference Base for Soil Resources (WRB) system [ 30 ] (pH 5.8), were collected from the UFH farm. The soil was watered to field capacity and incubated with Al sulphate (Al 2 [SO 4 ] 3 ) for 48 h before planting.…”

“…Although field testing has proved to be the most effective in testing maize genotypes for Al tolerance, it is very expensive and time-consuming [ 11 , 12 ]. Laboratory- or greenhouse-based testing techniques offer cheap, easy, and quick alternatives to screening large sets of genotypes for Al tolerance [ 13 , 14 ]. The other advantage of laboratory- and greenhouse-based testing methods is that they are very amenable to seedling-stage testing techniques.…”

“…The nutrient solution method is the most used laboratory-based technique, while the soil bioassay, also known as the pot-based method, is the most popular greenhouse-based technique for testing plant seedlings for tolerance to Al toxicity [ 13 , 14 ]. These two methods provide adequate Al stress to the plants, allowing the effective preliminary testing of many genotypes in a small area and consequently reducing the number of promising genotypes to be taken to the field for further analysis.…”

Evaluation of the growth and tolerance of maize lines under aluminum stress

“…It indicates that the maize line has a critical limit to survive under certain stress conditions. Zishiri et al (2022) also reported no hematoxylin stains on the roots of Al-tolerant inbred lines.…”

“…Root length is an important trait in measuring maize tolerance to Al stress, which is influenced by the action of additive and nonadditive genes (Ndeke and Tembo 2019). Al concentrations for testing the tolerance level of maize genotypes through a nutrient culture based on relative root growth ranged from 6-16 ppm (Giannakoula et al 2010;Zishiri et al 2022).…”