Abstract
Boron (B) is an important micronutrient required for the normal growth and development of plants. However, its excess in the soil causes severe damage to plant tissues, which affects the final yield. Wheat, one of the main staple crops, has been reported to be largely affected by B toxicity stress in arid and semi-arid regions of the world. The prevalence of B toxicity stress can be addressed by utilizing wild wheat genotypes with a variant level of stress tolerance. Wild wheat relatives have been identified as a prominent source of several abiotic stress-tolerant genes. However, Aegilops species in the tertiary gene pool of wheat have not been well exploited as a source of B toxicity tolerance. This study explores the root and shoot growth, proline induction, and extent of lipid peroxidation in 19 Aegilops accessions comprising 6 different species and the B-tolerant check wheat cultivar Bolal 2973 grown under Control (3.1 μM B), toxic (1 mM B), and highly toxic (10 mM B) B stress treatment. B toxicity stress had a more decisive impact on growth parameters as compared to the malondialdehyde (MDA) and proline content. The obtained results suggested that even the genotypes with high shoot B (SB) accumulation can be tolerant to B toxicity stress, and the mechanism of B redistribution in leaves should be studied in detail. It has been proposed that the studied Aegilops accessions can be potentially used for genetically improving the B toxicity-tolerance trait due to a high level of variation in the response toward high B toxicity. Though a number of accessions showed suppression in the root and shoot growth, very few accessions with stress adaptive plasticity to B toxicity stress leading to an improvement of shoot growth parameters could be determined. The two accessions, Aegilops biuncialis accession TGB 026219 and Aegilops columnaris accession TGB 000107, were identified as the potential genotypes with B toxicity stress tolerance and can be utilized for developing a pre-breeding material in B tolerance-based breeding programs.
Highlights
Boron (B) toxicity is a critical abiotic stress condition that has a detrimental effect on plant growth (Landi et al, 2019), limiting the agricultural yield in the different parts of the world, especially arid and semi-arid territories (Brdar-Jokanovic, 2020)
A set of 19 accessions consisting of diploid (Aegilops speltoides, Aegilops ligustica, and Aegilops umbellulata) and tetraploid (Aegilops biuncialis, Aegilops columnaris, and Aegilops triuncialis) progenitor species along with the Control wheat cultivar, Bolal 2973, were subjected to two different B toxicity stress conditions to evaluate their responses (Table 1)
The effect of B toxicity stress on the growth of 19 Aegilops accessions belonging to 6 different species was explored to identify the level of genetic variability in their tolerance to high B toxicity
Summary
Boron (B) toxicity is a critical abiotic stress condition that has a detrimental effect on plant growth (Landi et al, 2019), limiting the agricultural yield in the different parts of the world, especially arid and semi-arid territories (Brdar-Jokanovic, 2020). Its excess leads to additional accumulation in apoplastic and symplastic tissues binding with molecules, including sugar molecules, glycoproteins, glycolipids, and ribose containing compounds such as RNA, ATP, and NADPH (Reid et al, 2004), and hampering important processes such as cell division, photosynthesis, and stomatal conductance (Papadakis et al, 2004; Landi et al, 2012). Along with the hindrance in root growth, the main symptoms of B toxicity include necrosis on leaf tips and chlorosis, which results from the production of reactive oxygen species (ROS) (Cervilla et al, 2007; Wang et al, 2010; Sakamoto et al, 2011). Greater genetic diversity in the gene pool of a plant species is a desirable character that can help to deal with the problem of B toxicity stress
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