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The effect of gypsum (CaSO 4 ) amendment in the reduction of Al phytotoxicity of blueberry cultivars differing in Al resistance (Legacy and Brigitta, Al-resistant and Bluegold, Al-sensitive) was studied in a Hoagland's nutrient solution under acidic conditions for 2 weeks. Treatments were: Control (Hoagland solution), 2.5 mM CaSO 4 , 5 mM CaSO 4 , 100 µM Al (AlCl 3 ), 100 µM Al + 2.5 mM CaSO 4 , 100 µM Al + 5 mM CaSO 4 . Physiological, biochemical and chemical features of leaves and roots were determined to establish the amendment efficiency in the reduction of Al toxicity in these cultivars. Results showed that under Al toxicity the three investigated cultivars accumulated high Al concentrations in leaves and roots. These concentrations decreased with CaSO 4 application. Statistically significant interactions among Al in leaves but not in roots (p=0.719) and cultivars (p<0.001), were found. The lowest Ca concentration was found in the most Al-sensitive cultivar (Bluegold) and the highest in the more Al-resistant cultivars (Legacy and Brigitta). Among the underlying processes affected by Al stress in these blueberry cultivars the most evident changes were exhibited by the Al-sensitive cultivar Bluegold, where the photosynthetic performance decreased showing a slight recovery in presence of gypsum amendment at the end of experiment. Instead, the more Al-resistant cultivar (Legacy) did not change its photosynthetic parameters in presence of the gypsum amendments during the treatment, whereas in Brigitta, only a slight recovery at the end of treatment was evidenced by the gypsum application. Thus, in relation to these parameters the gypsum amendment was efficient in complete recovery from the toxic Al effect in the Al-resistant cultivar Brigitta and a slight recovery of the toxic Al effect in the Al-sensitive cultivar Bluegold. Nonetheless, this amendment is a good alternative to ameliorate Al toxicity in Al-sensitive cultivars and additionally provides a good source of Ca and S.

Salinization of soils and freshwater resources by natural processes and/or human activities has become an increasing issue that affects environmental services and socioeconomic relations. In addition, salinization jeopardizes agroecosystems, inducing salt stress in most cultivated plants (nutrient deficiency, pH and oxidative stress, biomass reduction), and directly affects the quality and quantity of food production. Depending on the type of salt/stress (alkaline or pH-neutral), specific approaches and solutions should be applied to ameliorate the situation on-site. Various agro-hydrotechnical (soil and water conservation, reduced tillage, mulching, rainwater harvesting, irrigation and drainage, control of seawater intrusion), biological (agroforestry, multi-cropping, cultivation of salt-resistant species, bacterial inoculation, promotion of mycorrhiza, grafting with salt-resistant rootstocks), chemical (application of organic and mineral amendments, phytohormones), bio-ecological (breeding, desalination, application of nano-based products, seed biopriming), and/or institutional solutions (salinity monitoring, integrated national and regional strategies) are very effective against salinity/salt stress and numerous other constraints. Advances in computer science (artificial intelligence, machine learning) provide rapid predictions of salinization processes from the field to the global scale, under numerous scenarios, including climate change. Thus, these results represent a comprehensive outcome and tool for a multidisciplinary approach to protect and control salinization, minimizing damages caused by salt stress.

Blueberry (Vaccinium corymbosum L.) is well adapted to acidic soils where aluminum (Al 3+ ) can be linked to oxidative stress and antioxidant capacity (AC). Calcium sulfate (CaSO 4 ) is used to alleviate Al 3+ because it does not alter soil acidity. However, the role of Ca addition in AC, based on a single electron transfer reaction (SET), remains unknown. The aim was to evaluate the AC using SET methodologies, i.e., 2,2-diphenyl-2-picrylhydrazyl (DPPH), 2,2´-Azinobis-bis (3 ethylbenzothiazoline-6-sulphonic acid) (ABTS) and ferric reducing-antioxidant power (FRAP). Bueberry cultivars Elliot and Jersey were grown and exposed to the following treatments for 15 days: Control (nutrient solution alone, pH 4.5); control+Al (Al); control+Al+Ca (Al+Ca) and control+Ca (Ca). The Ca and Al concentrations, total phenol (TP) content and radical scavenging activity (RSA) were evaluated at 7 and 15 days. The Al+Ca and Ca treatments increased the Ca concentration in the leaves (22%) and roots (40%) of both cultivars compared with the control. The Ca in the tissues varied with cultivar and time. After 15 days, increases in TP, DPPH, ABTS and FRAP were detected. The cultivars showed positive relationships between the TP and AC in the leaves and roots. Thus, CaSO 4 is an important tool to improve the AC in Al-stressed fruit crops grown in acid soils.

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R. Carrillo, J. Guerrero, M. Rodríguez, and C. Meriño-Gergichevich. 2015. Colonization of blueberry (Vaccinium corymbosum L.) plantlets by ericoid mycorrhizae under nursery conditions. Cien. Inv. Agr. 42(3): 365-374. The ericoid mycorrhiza is a symbiotic interaction that contributes to the improvement of the establishment and production of blueberries (Vaccinium corymbosum L.). The objectives of this paper were to assess the frequency (%) and intensity (%) of the colonization and growth of blueberry plantlets inoculated with ericoid mycorrhizae collected from three different edaphoclimatic conditions in the La Araucanía region of southern Chile under nursery conditions. Plantlets of three blueberry cultivars ("Brigitta", "Duke" and "Legacy") were grown under nursery conditions in sterile peat moss and a vermiculite substrate with fresh ericoid mycorrhizae propagules from Gaultheria pumila (collected in Villarrica National Park), Azalea sp., (from an urban garden in Temuco) or V. corymbosum cv. "Brigitta" (from an organic farm in Temuco). After six months, the development of hyphae characteristic of ericoid micorrhizal fungi was identified in root cells. The frequency and intensity of colonization was greater in the "Duke" cv. given the inoculum derived from V. corymbosum, followed by the "Brigitta" and "Legacy" cultivars treated with inoculum from the G. pumila inoculum. Colonization was lowest in those plants treated with the Azalea sp. inoculum. Contact between the inoculum sources and the fine roots of the micro-propagated blueberry plantlets under nursery conditions for six months was an effective method to promote mycorrhization. However, the development of mycorrhizae did not enhance the growth of the three blueberry cultivars during the evaluation period. The possibility of selecting ericoid inocula from site-specific conditions in southern Chile may eventually be used to support the micro-propagation of blueberry plantlets during acclimation and planting, assuming that mycorrhizal plants will improve conditions for establishment in the field.

Boron (B) is an essential micronutrient required for physiological and biochemical processes in fruit crops such as highbush blueberry (Vaccinium corymbosum L.), well adapted species to acidic soils (pH water ≤ 5.5) with relatively low B availability. However, an optimal range of B supplies is quite narrow, particularly among cultivars, making it easy to under-or over-fertilize which could lead to boron toxicity. Under controlled conditions, cultivars Brigitta and Legacy were grown in a peat moss substrate (pH 4.5) with five B concentrations (0, 50, 200, 400 and 800 µM). Plant biomass, nutrient concentration, water potential (Ψ leaf ), oxidative stress and antioxidant activity were determined at 30 d. Concentrations of 400 and 800 µM B reduced shoot and root growth in both cultivars, and 800 µM B decreased Ψ leaf in Legacy and significantly increased it in Brigitta. Boron applied at 400 µM resulted in the highest B accumulation in leaves of Brigitta (5-fold) and Legacy (2-fold), whereas Brigitta roots showed up to 60% increased B accumulation in comparison with 50 µM B, respectively. High B caused more severe oxidative stress in leaves of Legacy than B deficiency. The antioxidant activity was increased from 50 to 400 µM B in both cultivars. Boron added at 400 and 800 µM impaired physiological and biochemical performance probably due to toxicity, demonstrating that highbush blueberry in a genotype-dependent manner has relatively low B requirement.