Sérgio Tonetto de Freitas

Abscisic acid triggers whole-plant and fruit-specific mechanisms to increase fruit calcium uptake and prevent blossom end rot development in tomato fruit

Calcium (Ca) uptake into fruit and leaves is dependent on xylemic water movement, and hence presumably driven by transpiration and growth. High leaf transpiration is thought to restrict Ca movement to low-transpiring tomato fruit, which may increase fruit susceptibility to the Ca-deficiency disorder, blossom end rot (BER). The objective of this study was to analyse the effect of reduced leaf transpiration in abscisic acid (ABA)-treated plants on fruit and leaf Ca uptake and BER development. Tomato cultivars Ace 55 (Vf) and AB2 were grown in a greenhouse environment under Ca-deficit conditions and plants were treated weekly after pollination with water (control) or 500 mg l(-1) ABA. BER incidence was completely prevented in the ABA-treated plants and reached values of 30-45% in the water-treated controls. ABA-treated plants had higher stem water potential, lower leaf stomatal conductance, and lower whole-plant water loss than water-treated plants. ABA treatment increased total tissue and apoplastic water-soluble Ca concentrations in the fruit, and decreased Ca concentrations in leaves. In ABA-treated plants, fruit had a higher number of Safranin-O-stained xylem vessels at early stages of growth and development. ABA treatment reduced the phloem/xylem ratio of fruit sap uptake. The results indicate that ABA prevents BER development by increasing fruit Ca uptake, possibly by a combination of whole-plant and fruit-specific mechanisms.

Dynamic Alternations in Cellular and Molecular Components during Blossom-End Rot Development in Tomatoes Expressing sCAX1, a Constitutively Active Ca2+/H+ Antiporter from Arabidopsis

Although calcium (Ca) concentration in cellular compartments has been suggested to be tightly regulated, Ca deficiency disorders such as blossom-end rot (BER) in tomato (Solanum lycopersicum) fruit may be induced by abnormal regulation of Ca partitioning and distribution in the cell. The objectives of this work were to analyze the effects of high expression of the constitutively functional Arabidopsis (Arabidopsis thaliana) Ca2+/H+ exchanger (sCAX1) tonoplast protein in tomato fruit on cellular Ca partitioning and distribution, membrane integrity, and the transcriptional profile of genes potentially involved in BER development. Wild-type and sCAX1-expressing tomato plants were grown in a greenhouse. Wild-type plants did not develop BER, whereas sCAX1-expressing plants reached 100% BER incidence at 15 d after pollination. The sCAX1-expressing fruit pericarp had higher total tissue and water-soluble Ca concentrations, lower apoplastic and cytosolic Ca concentrations, higher membrane leakage, and Ca accumulation in the vacuole of sCAX1-expressing cells. Microarray analysis of healthy sCAX1-expressing fruit tissue indicated down-regulation of genes potentially involved in BER development, such as genes involved in membrane structure and repair and cytoskeleton metabolism, as well as up-regulation of genes that may have limited BER damage expansion, such as genes coding for heat shock proteins, glutathione S-transferases, and peroxidases. The results indicate that the high expression of the sCAX1 gene reduces cytosolic and apoplastic Ca concentrations, affecting plasma membrane structure and leading to BER symptom development in the fruit tissue.

Calcium partitioning and allocation and blossom-end rot development in tomato plants in response to whole-plant and fruit-specific abscisic acid treatments

ABA prevented blossom-end rot development in tomato fruit by whole plant and fruit specific mechanisms. At the whole plant level, ABA increased fruit Ca2+ uptake. At the fruit specific level, ABA increased fruit tissue water-soluble apoplastic Ca2+ concentration

Comparing the analytical performances of Micro-NIR and FT-NIR spectrometers in the evaluation of acerola fruit quality, using PLS and SVM regression algorithms

The main goal of this study was to investigate the analytical performances of a state-of-the-art device, one of the smallest dispersion NIR spectrometers on the market (MicroNIR 1700), making a critical comparison with a benchtop FT-NIR spectrometer in the evaluation of the prediction accuracy. In particular, the aim of this study was to estimate in a non-destructive manner, titratable acidity and ascorbic acid content in acerola fruit during ripening, in a view of direct applicability in field of this new miniaturised handheld device. Acerola (Malpighia emarginata DC.) is a super-fruit characterised by a considerable amount of ascorbic acid, ranging from 1.0% to 4.5%. However, during ripening, acerola colour changes and the fruit may lose as much as half of its ascorbic acid content. Because the variability of chemical parameters followed a non-strictly linear profile, two different regression algorithms were compared: PLS and SVM. Regression models obtained with Micro-NIR spectra give better results using SVM algorithm, for both ascorbic acid and titratable acidity estimation. FT-NIR data give comparable results using both SVM and PLS algorithms, with lower errors for SVM regression. The prediction ability of the two instruments was statistically compared using the Passing-Bablok regression algorithm; the outcomes are critically discussed together with the regression models, showing the suitability of the portable Micro-NIR for in field monitoring of chemical parameters of interest in acerola fruits.

Short anaerobiosis period prior to cold storage alleviates bitter pit and superficial scald in Granny Smith apples.

BACKGROUND Californian Granny Smith apples are very susceptible to bitter pit (BP) and superficial scald symptoms that develop during cold storage. The main preventive means are diphenylamine dipping and/or gaseous application of the ethylene inhibitor 1-methylcylclopropene (1-MCP), which is effective against superficial scald but not against BP. This study investigated the efficacy of a non-chemical alternative, low-O(2) (LO2) stress, in preventing these two physiological disorders. RESULTS Application of LO2 stress at 20 degrees C for 10 days prior to cold storage of Granny Smith apples reduced superficial scald and BP incidence and severity during 8 months at 0 degrees C. LO2 treatments induced volatile alcohols and reduced ethylene and 6-methyl-5-hepten-2-one (MHO-on) production, thereby reducing superficial scald development after 4 months at 0 degrees C. In addition, LO2-treated fruits had higher pectin methyl esterase (MdPME) gene expression, similar to that of 1-MCP-treated fruits, associated with their higher firmness. Conversion of MHO-on to 6-methyl-5-hepten-2-ol (MHO-ol) in LO2-treated fruits may explain the lower scald development. CONCLUSION The ratio between MHO-on and MHO-ol might serve as an index of superficial scald severity. Reduction of BP symptoms in LO2-treated fruits could be due to accumulation of volatile alcohols in the peel tissue.

Role of pectin methylesterases in cellular calcium distribution and blossom‐end rot development in tomato fruit

Blossom-end rot (BER) in tomato fruit (Solanum lycopersicum) is believed to be a calcium (Ca²⁺) deficiency disorder, but the mechanisms involved in its development are poorly understood. Our hypothesis is that high expression of pectin methylesterases (PMEs) increases Ca²⁺ bound to the cell wall, subsequently decreasing Ca²⁺ available for other cellular functions and thereby increasing fruit susceptibility to BER. The objectives of this study were to evaluate the effect of PME expression, and amount of esterified pectins and Ca²⁺ bound to the cell wall on BER development in tomato fruit. Wild-type and PME-silenced tomato plants were grown in a greenhouse. At full bloom, flowers were pollinated and Ca²⁺ was no longer provided to the plants to induce BER. Our results show that suppressing expression of PMEs in tomato fruit reduced the amount of Ca²⁺ bound to the cell wall, and also reduced fruit susceptibility to BER. Both the wild-type and PME-silenced fruit had similar total tissue, cytosolic and vacuolar Ca²⁺ concentrations, but wild-type fruit had lower water-soluble apoplastic Ca²⁺ content and higher membrane leakage, one of the first symptoms of BER. Our results suggest that apoplastic water-soluble Ca²⁺ concentration influences fruit susceptibility to Ca²⁺ deficiency disorders.

Qualidade para processamento de clones de batata cultivados durante a primavera e outono no Rio Grande do Sul

A industrializacao da batata (Solanum tuberosum L.) tem sido limitada no Brasil, quase que exclusivamente, pela falta de materia-prima adequada. Alta qualidade do produto processado e dependente de altos teores de materia seca, que reduz a absorcao de oleo durante a fritura e confere crocância, e baixos teores de acucares redutores, que mantem a coloracao clara das fritas. O objetivo deste trabalho foi identificar clones de batata de alta qualidade para processamento a partir da avaliacao de tuberculos produzidos durante os cultivos de primavera de 2003 e outono de 2004 em Santa Maria, RS. O experimento foi conduzido em um fatorial (15 clones e duas epocas de cultivo) no delineamento de blocos ao acaso, com quatro repeticoes. Foram avaliados os clones Dakota Rose, SMINIAIpora, SMIJ461-1, SMIJ319-1, SMIJ456-4Y, SMID040-4RY, SMIE040-6RY, SMIC148-A, SMIF165-6RY, SMIH095-1, SMINIA90244-1, SMINIA793101-3, SMINIA95043-11, Macaca e Asterix nos cultivos de primavera de 2003 e outono de 2004 em Santa Maria, RS. As condicoes ambientais, durante o periodo de producao, influenciaram a qualidade pos-colheita dos tuberculos. Os clones SMIJ461-1, SMIJ319-1, SMIJ456-4Y, SMIC148-A, SMIDO40-4RY e SMIH095-1 foram os que apresentaram o melhor desempenho nas caracteristicas desejaveis para processamento, sendo superiores a Asterix, cultivada para consumo de mesa ou para processamento na forma de chips nas diferentes regioes produtoras de batata. Dentre esses clones, SMIDO40-4RY e SMIH095-1 foram os menos influenciados pelas diferencas de temperatura e insolacao tipicas das epocas de cultivo de outono e primavera no RS. Os clones SMIJ461-1 e SMIJ456-4Y apresentaram maior teor de materia seca e coloracao mais clara do chips no cultivo da primavera.

Conservação de três genótipos de feijão (Phaseolus vulgaris L.) do grupo carioca em armazenamento refrigerado e em atmosfera controlada

Engenheiro Agronomo, Doutora, Professora, UFSM.RESUMOO objetivo deste trabalho foi de avaliar o efeito doarmazenamento refrigerado (AR) e de atmosfera controlada(AC), sobre a cor do tegumento, germinacao, umidade do grao,ocorrencia de pragas e facilidade de cozimento de tres genotiposde feijao do grupo carioca (‘Carioca’, ‘Perola’ e a linhagemM91-012). O delineamento experimental utilizado foiinteiramente casualizado, com tres repeticoes, com os seguintestratamentos: ar em temperatura ambiente (convencional);armazenamento refrigerado a 0oC (AR); fluxo de N

Effect of 1-MCP applied at different times during cold and Ca storage

ABSTRACT - The objective of this work was to evaluate the effect of 1-MCP applied at different period during the cold storage (CS) and in controlledatmosphere (CA) on the quality of ‘Quioto’. Persimmon. The experimental design was completely randomized with four replication s of 30 fruits andthe tested treatments were: cold storage (CS), cold storage + 1-MCP (1000ppb) in the beginning of the storage, cold storage + 1-MCP (1000ppb) in theend of the storage period; storage in controlled atmosphere (CA) with 1kPa of O 2 and 5kPa of CO 2 and 1kPa of O 2 and 5kPa of CO 2 + 1-MCP in the endof the storage, after 2 months of storage at –0.5°C, plus 5 days at 10°C and 3 days at 20°C. In the cooled storage, the 1-MCP, applied as in thebeginning of the storage as in the end of the storage, provided greater pulp firmness. For the parameters: total soluble solids, rottenness anddarkening of the peel didn’t have statistics difference between the treatments. There were no statistics differences between th e treatments for totalsoluble solids, rottenness and darkning of the peel. In conclusion 1-MCP applied in the beginning or end of storage period mant ained high firmmness.

Processing quality of potato tubers produced during autumn and spring and stored at different temperatures

The objective of this work was to access processing quality of potato clones (Solanum tuberosum) Asterix, SMINIA793101-3, and Missaukee cultivated during spring and autumn growing seasons and stored at 4, 8, 12, or 25oC. Clones grown in spring had shorter dormancy than clones grown in autumn. Potato tubers grown in spring and autumn and stored at 4oC, as well as tubers grown in autumn and stored at 8oC had no sprouting for six months. Among clones grown in autumn, the longest dormancy period during storage at 12oC was observed in the clone SMINIA793101-3, and at 25oC was in the clone Asterix. In potato tubers grown in spring, the longest dormancy period during storage at 8oC was observed in the clones SMINIA793101-3 and Missaukee, at 12oC was in the clone SMINIA793101-3, and at 25oC was in the clones Asterix and Missaukee. Potato tubers grown in spring had higher dry matter, starch content, and respiration rates, and lower reducing sugar, and total polyphenol content. The only exception was the Missaukee that had similar dry matter content in both growing seasons. In general, storage at 4oC and 8oC were more effective in reducing respiration rates and maintaining higher dry mater content of potato tubers. Chip darkening, reducing sugars, and total polyphenol content increased during storage of potato tubers. Darker chip color, higher reducing sugars and polyphenol content were obtained during storage at temperatures of 4oC and 8oC. These results suggest that the best storage temperature depends on genotype, tuber physiological age, and growing conditions.