Differential mechanisms between traditionally established and new highbush blueberry (Vaccinium corymbosum L.) cultivars reveal new insights into manganese toxicity resistance.

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 ß-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.

Concentrations of cytokinin and the use of agricultural residues in the in vitro propagation media of highbush blueberry / Concentrações de citocinina e uso de resíduos agrícolas no meio de multiplicação in vitro de mirtileiro

The objective of the research was to evaluate cytokinin concentrations and agricultural residues as physical structuring agents of the culture medium in the in vitro propagation of highbush blueberry (Vaccinium corymbosum Duke). To that end, three different concentrations of 2-isopentenyladenine (2iP) (0, 5, and 10 mg L-1)in woody plant medium (WPM) and five structuring agents (in natura rice husks, carbonized rice husks, coconut fiber, S-10 Beifort®, and agar)were tested. After 60days of culture, the following parameters were evaluated: survival (%),sprout and shoot lengths (cm),propagation rate, number of sprouts, and shoot dry mass (g). The substrates used as structuring agents were analyzed in terms of pH and electrical conductivity. The in natura rice husk, S-10 Beifort®, and carbonized rice husk did not differ from the agar in terms of the sprout length. The shoots were longer (1.64 cm) in cultures within natura rice husk than in other treatments. In the absence of 2iP, S-10 Beifort® resulted in the highest propagation rate (2.97). Concerning the number of sprouts, S-10 Beifort®, in natura rice husks, and carbonized rice husks did not differ from agar. However, when the regulator was added, the agar performed better in comparison to the other residues. Thus, in natura rice husks, carbonized rice husks, and S-10 Beifort®are potential physical structuring agents of the culture medium that can be used without 2iP.(AU)

O objetivo deste trabalho foi avaliar concentrações de citocinina e resíduos agrícolas como agentes físicos de estruturação do meio na multiplicação in vitro de mirtileiro (Vaccinium corymbosum) Duke. Para isso, foram testadas três concentrações de 2-isopenteniladenina (2iP) (0; 5 e 10 mg L-1) no meio WPM (Wood Plant Media); e cinco agentes estruturantes (casca de arroz in natura, casca de arroz carbonizada, fibra de coco, S-10 Beifort® e ágar). Após 60 dias foram avaliados: sobrevivência (%); comprimento de brotações e de parte aérea (cm); taxa de multiplicação; número de brotações e massa seca de parte aérea (g). Analisou-se os substratos utilizados como agentes estruturantes quanto ao pH e condutividade elétrica. A casca de arroz in natura, o S-10 Beifort®, e a casca de arroz carbonizada não diferiram do ágar quanto ao comprimento de brotações. Na casca de arroz in natura obteve-se o maior comprimento de parte aérea (1,64 cm), diferindo dos demais tratamentos. Na ausência de 2iP o S-10 Beifort® apresentou a maior taxa de multiplicação (2,97). Para o número de brotações o S-10 Beifort®, a casca de arroz in natura e carbonizada não diferiram do ágar. Entretanto, quando acrescido de regulador, o ágar apresenta um desempenho maior em relação aos resíduos. Sendo assim, a casca de arroz in natura, a casca de arroz carbonizada, e o S-10 Beifort® apresentam-se como potencias estruturadores físicos do meio de cultura, podendo ser utilizados sem o uso de 2iP.(AU)

Molecular characterisation of a calmodulin gene, VcCaM1, that is differentially expressed under aluminium stress in highbush blueberry.

Calmodulin (CaM), a small acidic protein, is one of the best characterised Ca(2+) sensors in eukaryotes. This Ca(2+) -regulated protein plays a critical role in decoding and transducing environmental stress signals by activating specific targets. Many environmental stresses elicit changes in intracellular Ca(2+) activity that could initiate adaptive responses under adverse conditions. We report the first molecular cloning and characterisation of a calmodulin gene, VcCaM1 (Vaccinium corymbosum Calmodulin 1), in the woody shrub, highbush blueberry. VcCaM1 was first identified as VCAL19, a gene induced by aluminium stress in V. corymbosum L. A full-length cDNA of VcCaM1 containing a 766-bp open reading frame (ORF) encoding 149 amino acids was cloned from root RNA. The sequence encodes four Ca(2+) -binding motifs (EF-hands) and shows high similarity (99%) with the isoform CaM 201 of Daucus carota. Expression analyses showed that following Al treatment, VcCaM1 message level decreased in roots of Brigitta, an Al-resistant cultivar, and after 48 h, was lower than in Bluegold, an Al-sensitive cultivar. VcCAM1 message also decreased in leaves of both cultivars within 2 h of treatment. Message levels in leaves then increased by 24 h to control levels in Brigitta, but not in Bluegold, but then decreased again by 48 h. In conclusion, VcCaM1 does not appear to be directly involved in Al resistance, but may be involved in improved plant performance under Al toxicity conditions through regulation of Ca(2+) homeostasis and antioxidant systems in leaves.