Variability in Physiological Traits Reveals Boron Toxicity Tolerance in Aegilops Species

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.

Nutrient Homeostasis of Aegilops Accessions Differing in B Tolerance Level under Boron Toxic Growth Conditions

“…These accessions belong to six different Aegilops species counting A. biuncialis , A. columnaris , A. ligustica , A. speltoides , A. triuncialis , and A. umbellulata . Moreover, it is aimed to comprehend the importance of nutrient uptake in imparting high B tolerance to these Aegilops accessions by determining the correlation between the different studied nutrients and the previously published growth parameters based on data from the same hydroponic trial [ 26 ].…”

“…The immediate wheat relative, Aegilops, which fits in its tertiary gene pool, holds enormous potential for providing unique alleles to enhance this genetic variability in wheat. Regardless of the crossability and incompatibility issues, Aegilops species are being successfully used to develop tolerance against different abiotic and biotic stress conditions along with the other adaptive quality traits [ 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”

“…Despite lots of efforts towards employing Aegilops for different abiotic constraints, very less information is available on the B toxicity tolerance of Aegilops species. Although in the past few years, some studies described the disparity in B toxicity tolerance of different Aegilops species and genotypes [ 23 , 26 ], none of these focused on the uptake of nutrients in Aegilops species under B toxicity. Furthermore, the possible role of changes in nutrient uptake in providing B toxicity tolerance to them has not been examined.…”

“…Seeds of 19 Aegilops genotypes that were obtained from AARI National Gene Bank, İzmir, and Turkish Seed Gene Bank (TSGB), Ankara, Turkey as well as well-known B toxicity tolerant hexaploid wheat genotype, Bolal 2973 [ 24 , 25 ], were used to conduct this study ( Table 1 ). The material comprising of six diverse species along with the check cultivar was previously screened for B toxicity tolerance levels in terms of growth parameters, lipid peroxidation and proline analysis [ 26 ].…”

“…After harvest, growth parameters of the harvested root-shoot samples were estimated as mentioned by Khan et al [ 26 ]. For ICP-AES, from the same trial, root-shoot samples were cleaned with 0.1 N HCl and ultrapure water, and dried at 70 °C for 72 h followed by the pooling of the replicates and measurement of RDWs (root dry weight) and SDWs (shoot dry weights).…”