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In acid soils, manganese (Mn) concentration increases, becoming toxic to plants. Mn toxicity differentially affects physiological processes in highbush blueberry (Vaccinium corymbosum L.) cultivars. However, the mechanisms involved in Mn toxicity of the new and traditionally established cultivars are unknown. To understand Mn toxicity mechanisms, four traditionally established (Legacy, Brigitta, Duke, and Star) cultivars and two recently introduced to Chile (Camellia and Cargo) were grown under hydroponic conditions subjected to control Mn (2 μM) and Mn toxicity (1000 μM). Physiological, biochemical, and molecular parameters were evaluated at 0, 7, 14, and 21 days. We found that the relative growth rate was reduced in almost all blueberry cultivars under Mn toxicity, except Camellia, with Star being the most affected. The photosynthetic parameters were reduced only in Star by Mn treatment. Leaf Mn concentrations increased in all cultivars, exhibiting the lowest levels in Camellia and Cargo. Brigitta and Duke exhibited higher β-carotene levels, while Cargo exhibited a reduction under toxic Mn. In Legacy, lutein levels increased under Mn toxicity. Traditionally established cultivars exhibited higher antioxidant activity than the new cultivars under Mn toxicity. The Legacy and Duke cultivars increased VcMTP4 expression with Mn exposure time. A multivariate analysis separated Legacy and Duke from Camellia; Star and Cargo; and Brigitta. Our study demonstrated that Mn toxicity differentially affects physiological, biochemical, and molecular features in the new and traditionally established cultivars, with Legacy, Duke, Camellia, and Cargo as the Mn-resistant cultivars differing in their Mn-resistance mechanisms and Star as the Mn-sensitive cultivar.

Southern Chile has experienced a strong increase in sweet cherry production in recent years. However, there are climatic gaps that negatively reduce the fruit quality and yield of exportable fruit, such as the high incidence of rains during flowering and pre-harvest. The use of roof covers has become an agronomic solution that offers protection from weather events, such as rain, which will significantly increase the exportable fruit. However, the use of plastic covers can cause negative impacts on the fruit, such as a loss of firmness and acidity. Currently, the incidence of internal (pulp) browning has reduced the quality of cherries produced in Southern Chile, although research on this subject is largely under explored. Some studies reported that a high content of antioxidants in the fruit, both phenolic and non-phenolic (e.g., ascorbic acid), could reduce the incidence of the physiological disorder of browning. The soils of Southern Chile are characterized by the high content of organic matter, which implies high levels of available nitrogen (N) and a high phosphorus (P) content. Some studies, however, have shown that fertilization with N and P would significantly improve the postharvest quality, shelf life, and the accumulation of antioxidant compounds in fruits, even better than other strategies, including selenium and chitosan applications. However, there needs to be more detailed information on this aspect of the sweet cherry fruit production. The quality attributes and postharvest life of cherries are closely associated with the antioxidant levels of fruits, which could be related to either the soil acidity level of the Chilean Andisols or the levels of P and N in soil or plant tissues. Therefore, the objective of this review was to discuss the role of the N and P supply on the internal browning incidence in sweet cherries and relate it to what is known in other fruits.

Glyphosate is the most widespread herbicide for weed management, being extensively used in viticulture. In this study we tested, under field conditions, the effects of glyphosate applications on the quality of berry and wine, from cv. Ancellotta (Vitis vinifera L.), with particular regard to anthocyanin concentration and composition. Ripening and growth were monitored by analyzing berry technological parameters and weight. Additionally, microvinifications were performed, in order to analyze the concentration of anthocyanins, other flavonoids and phenolic acids in wine. Our findings indicated that, at harvest, both pH and anthocyanin concentration were significantly lower and titratable acidity higher in berries collected from vines of plots under glyphosate-treatment compared with those of non-treated parcels. Data suggest that treatment with glyphosate did not change the concentration of anthocyanins, other flavonoids and phenolic acids in the wine. Our results indicate that treatment with glyphosate may affect fruit metabolism and nutritional value in non-target plants.

Remote sensing based on visible and near infrared (VIS/NIR) reflectance is being recognized as a promising option to estimate water status in crops. In this research, we explored the relationship between the midday leaf water potential (ΨMD) and stomatal conductance (gs) with the normalized difference vegetation index (NDVI) and the water index (WI) in leaves of blueberry shrubs subjected to two irrigation treatments based on crop evapotranspiration (ETc): mild water deficit (60% of ETc) and full-irrigation (100% of ETc). Moreover, the impact of the irrigation doses on photosynthesis as well as on fruit yield and quality was assessed. Noteworthy, we detected positive correlations between ΨMD with NDVI (R2 = 0.61**; P

Deficiency or excess of nitrogen (N) supply can promote formation of reactive oxygen species in plants, inducing oxidative stress. Otherwise, plants may enhance phenolics biosynthesis and antioxidant capacity under N deficiency, but this effect is plant species-dependent. There is no information about influence on phenolics and antioxidant activity in highbush blueberry (Vaccinium corymbosum L.), in which quality and commercial importance depend on high phenolics concentration. We studied the effect of variable N supply (0 to 38 mM) on N uptake and antioxidant responses in two highbush blueberry cultivars (Legacy and Bluegold) hydroponically grown at the long-term. Nitrogen leaves concentration was enhanced for both cultivars at increasing N supply. Bluegold decreased CO2 assimilation at 0 N treatment, possibly due to both, insufficient N concentration and a decline in superoxide dismutase (SOD) activity. In contrast, SOD was activated in Legacy at 0 N, and interestingly only this cultivar maintained CO2 assimilation rates across all N treatments. Both cultivars showed higher phenolics and antioxidant activity levels at 9 mM. Despite the differential responses among the cultivars, we propose a threshold of 15 g N kg-1 DW to ensure high antioxidant activity and quality in blueberry leaves.

Manganese (Mn) toxicity limits plant growth in acid soils. Although Mn toxicity induces oxidative stress, the role of superoxide dismutase (SOD, EC.1.15.1.1) isoforms in conferring Mn tolerance remains unclear. Seedlings of ryegrass cultivars Nui (Mn-sensitive) and Kingston (Mn-tolerant) were hydroponically grown at 2.4 (optimal) or 750 μM Mn (toxic) concentration, and harvested from 2 to 48 h. Kingston showed higher shoot Mn than Nui at 2.4 μM Mn. At toxic supply, shoot Mn concentration steadily increased in both cultivars, with Kingston having the highest accumulation at 48 h. An early (2 h) increase in lipid peroxidation under Mn excess occurred, but it returned (after 6 h) to the basal level in Kingston only. Kingston exhibited higher SOD activity than Nui, and that difference increased due to toxic Mn. In general, Mn-induced gene expression of Mn- and Cu/Zn-SOD isoforms was higher in Nui than Kingston. Nevertheless, under Mn excess, we found a greater Fe-SOD up-regulation (up to 5-fold) in Kingston compared to Nui. Thus, Fe-SOD induction in Kingston might explain, at least partly, its high tolerance to Mn toxicity. This is the first evidence that Mn toxicity causes differential gene expression of SOD isoforms in ryegrass cultivars in the short-term.

E. Yanez-Mansilla, P. Cartes, M. Reyes-Diaz, A. Ribera-Fonseca, and M. Alberdi. 2014. Photosynthetic and antioxidant performance are differentially affected by short-term nitrogen supply in highbush blueberry cultivars. Cien. Inv. Agr. 41(1): 61-70. Nitrogen (N) is an essential nutrient for photosynthesis and may influence phenolic compound synthesis in higher plants. The effect of different amounts of N (0 to 38 mM) provided on a short-term (4 d) basis on the photosynthetic and antioxidant performance of highbush blueberry cultivars (Legacy and Bluegold) grown in a nutrient solution was studied. In both cultivars, the N concentration of leaves slightly increased in response to the N supply, with Bluegold frequently showing higher N concentrations than Legacy. Photosynthesis was reduced in Bluegold at the highest N dose, whereas in Legacy, a decrease of CO 2 assimilation occurred under N starvation. This decrease in photosynthesis was accompanied by enhanced lipid peroxidation but only in Bluegold. In both cultivars superoxide dismutase (SOD) was activated with an increasing N supply. Legacy also showed increased SOD activity to counteract oxidative stress at higher N levels. Radical scavenging activity was not affected by the N supply. However, the total phenols and anthocyanins steadily declined in the leaves of Legacy, and flavonoids were significantly increased in the roots of both cultivars with increasing N treatments. Thus, our findings indicate that blueberry cultivars exhibit differential sensitivity to short-term N stress, and SOD appears to be more involved than phenolic compounds in the amelioration of N-induced oxidative stress. Further studies are required to confirm the sensitivity to either N starvation in Legacy or N excess in Bluegold under long-term conditions.