ABSTRACT Water deficit is responsible for a negative impact on agricultural systems. Several physiological, biochemical, and molecular processes are initiated as a response to water-deficit stress. Quantifying the differential expression of the genes involved in the response to water-deficit stress plays a key role in the development of molecular strategies for engineering water-stress tolerance in plants. Therefore, the present study aims to evaluate the expression of key genes involved in the water-deficit response process in peach trees cv. Chimarrita grafted onto two different rootstocks. The experimental design was completely randomized, with four treatments that correspond to the evaluation periods: day zero (control), the fourth, seventh, and ninth days of water-deficit stress. Leaf samples of each Chimarrita/rootstock combination were analyzed separately. The expression of the genes related to ethylene biosynthesis, osmotic adjustment, and carbohydrate metabolism, namely ACC oxidase, GTL, SDH, SIP1, SOT1, S6PDH, and P5CS was quantified by real-time quantitative polymerase chain reaction (RT-qPCR). A differential response was observed in the expression of the SDH, GTL, P5CS, and SIP1 genes between Chimarrita/rootstock (Aldrighi 1 and Tsukuba 2)combinations. In both combinations of grafting, the S6PDH gene presented the highest level of expression at the fourth day of stress. These results show that genes related to carbohydrate and proline metabolism are important molecular markers to identify variability to water-deficit tolerance in Prunus persica.

Salinity is a limiting factor fot growth and development, since it affects several physiological processes in plants. This trial aimed to assess the levels of photosynthetic pigments, betacyanins, lipid peroxidation and activity of antioxidant enzymes in Alternanthera philoxeroides under salt stress. Plants originated from an in vitro culture were acclimatized and irrigated with sodium chloride (0, 200 and 400 mM) for 30 d. The experimental design was completely randomized with a 3×2 factorial arrangement of treatments: three concentrations of NaCl and two plant tissues (stems and leaves). The experimental data was subjected to an analysis of variance and means where compared using Tukey test (p≤0.05). The levels of chlorophylls a, chlorophylls b and total carotenoids presented similar responses, decreasing their values according to salt concentrations, while the chlorophyll a/b ratio of the plants that were submitted to the highest salt concentration presented a significant increase when compared to the control. Higher levels of betacyanin were observed on stems, when compared to the leaves, in the highest salt concentrations. On the leaves, there was a significant increase of lipid peroxidation and superoxide dismutase activity, whereas roots showed an increase of the enzymes catalase and ascorbate peroxidase. Salt stress caused greater degradation in the photosynthetic pigments, increment of betacyanin synthesis in stems, and damage to the cell membranes of the leaves. However, the increase of antioxidant enzymes activity stimulated the protective system against oxidative stress. It is concluded that Alternanthera philoxeroides (Mart.) Griseb. plants present reduction in levels of photosynthetic pigments, increased synthesis of betacyanins and increased activity of antioxidant enzymes in leaves and roots when exposed to salt stress.

La salinidad es un factor limitante para el crecimiento y el desarrollo, ya que afecta varios procesos fisiológicos en las plantas. Este estudio tuvo el objetivo de evaluar los niveles de pigmentos fotosintéticos, betacianinas, peroxidación lipídica y actividad de enzimas antioxidantes en Alternanthera philoxeroides bajo estrés salino. Las plantas se originaron de un cultivo in vitro y se aclimataron e irrigaron con cloruro de sodio (0, 200 y 400 mM) durante 30 d. El diseño experimental fue completamente aleatorio con un arreglo factorial 3×2 de los tratamientos: tres concentraciones de NaCl y dos tejidos vegetales (tallos y hojas). Los datos experimentales se sometieron a un análisis de varianza y las medias se compararon usando la prueba de Tukey (p≤0.05). Los niveles de clorofilas a, clorofilas b y carotenoides totales presentaron respuestas similares, disminuyeron sus valores con las concentraciones de sal, mientras que la relación de clorofila a/b de las plantas que se expusieron a la concentración mayor de sal presentó un incremento significativo respecto al control. Niveles mayores de betacianinas se observaron en los tallos, en comparación con las hojas, para las concentraciones de sal más altas. En las hojas hubo un aumento significativo de peroxidación lipídica y de actividad de superóxido dismutasa, mientras que las raíces mostraron un aumento en las enzimas catalasa y ascorbato peroxidasa. El estrés salino causó degradación mayor de los pigmentos fotosintéticos, un aumento en la síntesis de betacianinas en los tallos, y daño a las membranas celulares de las hojas. Sin embargo, el incremento de actividad de las enzimas antioxidantes estimuló el sistema protector contra el estrés oxidativo. Se concluye que las plantas de Alternanthera philoxeroides (Mart.) Griseb. presentan una reducción en los niveles de pigmentos fotosintéticos, mayor síntesis de betacianinas y mayor actividad de enzimas antioxidantes en las hojas y raíces cuando están expuestas a estrés salino.

A salinidade, dos solos e da água de irrigação, constitui fator limitante para o cultivo do arroz, principalmente nos estágios iniciais do desenvolvimento e no período de floração. A utilização de fontes de água de má qualidade para irrigação resulta no acúmulo de sais no solo, causando toxicidade importante na cultura. Uma solução para o problema seria a introdução de variedades com tolerância à salinidade elevada. Assim, objetivou-se com este trabalho avaliar a divergência genética entre genótipos de arroz visando à seleção de genótipos tolerantes à salinidade durante a fase vegetativa. Sementes de 10 genótipos de arroz foram cultivadas in vitro, em meio MS acrescido de 0 e 136 mM de NaCl. Após 21 dias, foram avaliados seis caracteres morfológicos e os resultados submetidos a análises multivariadas. Os métodos de otimização de Tocher, baseado na distância de Mahalanobis, e a dispersão gráfica das variáveis canônicas seguiram a mesma tendência de agrupamento dos genótipos, formando seis grupos distintos. A característica massa fresca da parte aérea foi a que mais contribuiu para a dissimilaridade genética entre os genótipos, pelo método de Singh, enquanto as duas primeiras variáveis canônicas foram suficientes para explicar 91,27% da variação observada. Nas condições experimentais testadas, os genótipos apresentaram graus distintos de tolerância à salinidade, sendo BRS Colosso, BRS Bojuru e BR IRGA 410, pertencentes aos grupos três e quatro, os que se mostraram mais tolerantes ao estresse salino e o genótipo Moti, pertencente ao grupo dois, o que se mostrou mais sensível.

Soil salinity is a limiting factor for rice cultivation, especially in the early stages of development and the flowering period. The use of sources of poor quality water for irrigation results in the accumulation of salts in the soil, causing major toxicity in culture. A solution to the problem would be the introduction of varieties with tolerance to high salinity. Hus the aim of this work is to evaluate genetic divergence among rice genotypes, aiming at the selection of genotypes tolerant to salinity during the vegetative phase. Seeds of 10 rice genotypes were grown in vitro on MS medium supplemented with 0 and 136 mM NaCl. After 21 days, six morphological characters were evaluated and the results subjected to multivariate analysis. The methods of Tocher, based on Mahalanobis distance, and graphic dispersion of canonic variables followed the same pattern of clustering structure, forming six groups. The characteristic of shoot fresh weight was the largest contributor to the genetic dissimilarity between genotypes by the method of Singh, while the other two canonic variables were sufficient to account for 91.27% of observed variation. Under the experimental conditions tested, the genotypes showed different degrees of salinity tolerance, while Colossus BRS, BRS Bojuru and BR IRGA 410, belonging to the groups three and four, were those who were more tolerant genotype and Moti, belonging to two what was more sensitive to salt stress.

As plantas em condições naturais estão expostas a vários estresses ambientais que afetam seu metabolismo. Dentre esses, a salinidade dos solos e da água de irrigação é um dos mais sérios problemas para a agricultura irrigada. O objetivo deste trabalho foi identificar, por meio de caracteres morfológicos, a variabilidade genética de 10 genótipos de arroz, cultivados in vitro, e agrupar esses genótipos para o caráter tolerância à salinidade. Os tratamentos foram constituídos por 10 genótipos e quatro concentrações de NaCl (0, 4, 8 e 12 mg L-1) acrescidas ao meio de cultura MS. Após 21 dias, foram avaliados diversos caracteres morfológicos, para os quais foram realizados cálculos percentuais de desempenho relativo (aumento ou redução), considerando-se o valor absoluto do tratamento-controle (0 mg L-1). Todos os caracteres mensurados tiveram seu desenvolvimento reduzido em substrato salino, sendo os correspondentes à biomassa média da parte aérea e do sistema radicular os mais sensíveis ao NaCl. Observou-se dissimilaridade entre os genótipos estudados para tolerância à salinidade, verificada pela formação de três grupos distintos pelo método hierárquico UPGMA e dois grupos pelo método de Tocher, sendo o genótipo BRS Bojuru o mais tolerante e BRS "7" Taim e BRS Ligeirinho os mais sensíveis à salinidade.

Plants under natural conditions are exposed to several environmental stresses which affect their metabolism. Among them, soil and irrigation water salinity is one of the most serious problems to irrigated agriculture. The aim of this work was to identify through morphologic characters, the genetic variability of 10 genotypes of rice cultivated in vitro, and classify these genotypes regarding salinity tolerance. The treatments were constituted by ten genotypes and four NaCl concentrations (0, 4, 8 and 12 mgL-1) added to MS culture medium. After 21 days, several morphological characters were evaluated, to which percentage calculations of relative performance (increase or reduction) were made, considering the absolute value of the control treatment (0mg L-1). All the measured characters had their development reduced in saline substrate. The most sensitive characters to NaCl concentration were mean biomass from the aerial parts and from the radicular system. Differences were observed among the genotypes studied regarding salinity tolerance. Three distinct groups were formed by the UPGMA hierarchical method and two groups by Tocher method, with BRS Bojuru genotype the most tolerant and BRS"7" Taim and BRS Ligeirinho the most sensitive to salinity.