Aluminum (Al) toxicity is a major agronomic problem in acid soils. Most studies regarding Al stress focus on phenomena occurring in the roots; however, less is known about the effects of Al stress on photosynthetic apparatus functionality. Our aim was to rank three highbush blueberry (Vaccinium corymbosum) cultivars according to their tolerance to acid and Al stresses. Additionally, the levels of Al toxicity for highbush blueberry were established. ‘Brigitta’, ‘Legacy’, and ‘Bluegold’ were grown in a greenhouse in hydroponic solutions containing different Al concentrations (0, 25, 50, 75, and 100 μm) for 0 to 48 h and were allowed to recover (without Al) over 24 h. In all Al-treated cultivars, root growth inhibition was found at the highest Al treatment. However, ‘Brigitta’ also showed root growth up to 75 μm Al. Photochemical parameters decreased substantially due to Al treatments in ‘Bluegold’ (up to 98% inhibition) and ‘Legacy’ (up to 80% inhibition) without total recovery. In contrast, ‘Brigitta’ showed a better photosystem II performance and root growth than the other cultivars. These results suggest that ‘Brigitta’ is the best cultivar for use in acid soils with Al toxicity, followed by ‘Legacy’. ‘Bluegold’ was highly sensitive to Al stress. In addition, Al toxicity levels for blueberries depend on the genotype studied.
Marjorie Reyes-Diaz, Miren Alberdi, and Maria de la Luz Mora
Marjorie Reyes-Díaz, Claudio Inostroza-Blancheteau, Rayen Millaleo, Edgardo Cruces, Cristián Wulff-Zottele, Miren Alberdi, and María de la Luz Mora
We compared the aluminum tolerance of two highbush blueberry (Vaccinium corymbosum) cultivars, Legacy and Bluegold, grown in a greenhouse in Hoagland's solution with increasing concentrations of Al (0, 25, 50, 100, and 200 μm) for 7 to 20 days, using root lipid peroxidation (LP), radical scavenging activity (RSA), Al uptake by roots, and relative growth rate (RGR) as criteria. Leaf physiological [photochemical and non-photochemical parameters of photosystem II (PSII)] and biochemical (pigments, LP, RSA, and total soluble carbohydrates) responses to Al stress were also analyzed and then a principal component analysis (PCA) was performed. The results indicated that ‘Bluegold’ showed the highest Al uptake and LP in roots and a lower RGR in contrast to ‘Legacy’. The photochemical parameters were more affected in ‘Bluegold’ than in ‘Legacy’, particularly at the beginning of the experiment. At this point, a sharp increase in RSA was found in ‘Legacy’. According to these parameters, ‘Legacy’ was more Al tolerant than ‘Bluegold’. PCA revealed that among the underlying processes affected by Al toxicity in the highbush blueberry, the photochemical efficiency of PSII followed by modifications of photosynthetic pigment contents are of greatest significance after long-term Al stress. Additionally, RSA plays an important role in the long-term acclimation response mechanisms to Al stress in highbush blueberry leaves.