Abstract
Two wheat (Triticum aestivum L.) Madeiran landraces were subjected to 100 μM and 200 μM of aluminium (Al) in hydroponic culture, assessing the organic acid exudation role in plant’s responses to this metal. Samples of initial landrace populations (F0), F3 and haplodiploid lines (DH) were evaluated using standard tests: eriochrome cyanine R staining, root elongation and callose accumulation in roots. Root exudates were obtained to determine if the accumulation of malic and citric acids in hydroponic medium was a response to Al exposure. Additionally, the presence of ALMT1 gene was determined using five microsatellite markers. Standard tests confirmed that ISOP 76 was Al tolerant and ISOP 239, Al susceptible. ISOP 76, in the presence of 100 μM Al, exuded substantially more malic acid (12.87 to 43.33 mg/L), than ISOP 239 (3.65 to 7.72 mg/L). The levels of both organic acid exudation were substantially lower in ISOP 239 than in the ISOP 76. In the presence of 200 μM Al, ISOP 76 F0 shows a higher root elongation ratio (better tolerates Al), but the DH line was the one that exuded higher content of malic acid. Different gene alleles and promoters were detected in both landraces. Molecular differences could explain the observed dissimilarity in organic acid exudation response to Al stress.
Highlights
Wheat is the third most harvested cereal worldwide (Shewry 2009)
The F0 generation of ISOP 239 had more than 55% of susceptible individuals and this susceptibility increased with the selection (Fig. 1)
Results of root elongation and root elongation ratio are higher in the ISOP 76 than in ISOP 239, and even comparable with Maringaroot elongation ratio
Summary
Wheat is the third most harvested cereal worldwide (Shewry 2009). In many parts of the world, wheat is cultivated on acidic soils that affect 40% of arable land globally (Yang et al 2012). Soil acidity is one of the main constrains of high wheat yield, with low pH (below 4.5) making aluminium cationic form to become bioavailable to plant roots, affecting their growth and capacity to uptake water and nutrients (Ma et al 2001). Screening of wheat genetic resources under such edaphic conditions and understanding mechanisms of aluminium tolerance are vital. Different physiological tests have been developed to assess plants’ Al tolerance, including measurements of root elongation, staining with eriochrome cyanide R and quantification of callose accumulation in root tips (Pinheiro de Carvalho et al 2003, dos Santos et al 2005)
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