Blossom-end rot (BER) is a physiological disorder that can affect 100% of the fruit crop depending on the genotype. Tomato varieties with elongated fruit usually have a greater susceptibility to BER than other varieties. To evaluate and identify the possible physiological and morphological characteristics related to the onset of BER development, four varieties of long-shape tomato fruit with different susceptibility to BER: ‘San Marzano,’ ‘Banana Legs,’ ‘Roma,’ and ‘Mini-Roma’ were examined. Our results show that ‘San Marzano’ and ‘Banana Legs’ (elongated fruit) had a higher incidence of BER and lower Ca2+ concentration in the distal fruit tissue. ‘San Marzano’ (the most elongated fruit) presented higher electrolyte leakage in the distal fruit tissue. By comparison, ‘Roma’ and ‘Mini-Roma’ (less elongated fruit) were less susceptible to BER and had a higher ratio for proximal/distal fruit Ca2+ and a lower distal cell-wall bound content of Ca2+. Additionally, xylem functionality (vessels transporting water and solutes) in the distal fruit tissue was also higher in these more-tolerant varieties. These results support the theory that total fruit content of Ca2+ is not the only factor determining fruit susceptibility to BER, but rather a balance between physiological and morphological factors that influence Ca2+ transport and allocation in the fruit.
Calcium (Ca 2+) is an essential macronutrient in plants, and low concentrations of this nutrient may result in development of a physiological disorder known as blossom-end rot (BER) in tomato. Hormones can regulate the accumulation of Ca 2+ and, consequently, fruit susceptibilities to BER. The objective of this study was to evaluate the effect of gibberellin (GA), abscisic acid (ABA), and 24-epibrassinolide (EBL) on Ca 2+ accumulation and BER incidence in tomato. The 'Tyna c.v' tomato plants were sprayed biweekly, during anthesis, with water (control), GA (28.9 µmol L-1), ABA (90.8 µmol L-1 and 136.2 µmol L-1), EBL (0.01 µmol L-1 and 0.1 µmol L-1). Treatments were applied until the physiological maturity of fruits of the first raceme in a completely randomized design and then, the following evaluations were performed: percentage of BER, growth evaluations, Ca 2+ contents, physicalchemical parameters in fruits, stomatal conductance and transpiration. ABA and EBL treatments reduced BER incidence in a range of 6.6 to 9.0 %. The bioregulators used had no effect on plant growth, fruit diameter, length, or color. However, application of GA and EBL reduced titratable acidity and, the first also reduced soluble solids content in the fruit. All treatments, except GA treatment, increased Ca 2+ contents in the fruits, when compared with the control. The highest fruit Ca 2+ content was observed in plants treated with 0.01 µmol L-1 of EBL. According to our results, ABA and EBL increased Ca 2+ concentrations and decreased BER incidence and thus there is a great potential for their use in agriculture in tomato fruit.
Water stress leads to large productivity losses in rice cultivation, and plant hormones play a key role in the plant strategies to prevent the harmful effects of water stress in crop development. The objective of this work was to investigate the effects of brassinosteroids (BRs) in rice development and yield under irrigation and under water deficit conditions applied during the preanthesis period. Exogenous applications of bioregulators were performed through leaf spray. Two dosages of 24-epibrassinolide (EBL) were applied (0.01 μM and 0.1 μM), in addition to two dosages of ABA (2.27 mM and 4.54 mM) in order to compare the effects, considering its already known beneficial effects in response to drought adaptation. Plants of the cultivar IRGA 424RI grown under greenhouse conditions were submitted to water deficit from V13 stage until reaching a leaf water potential of-2 MPa. Physiological, growth and biochemical parameters were measured. Even though the water stress reduced plant growth, 0.01µ M EBL-treated plants presented unchanged initial dry weight, height and tillering after the stress imposition. The 0.1 µM EBL-treated plants maintained the total dry weight of grains even after water stress imposition, while control and ABA-treated plants showed a 63.9% and 28.1-58.6% reduction, respectively. The 0.01 µM EBL treatment doubled the contents of chlorophyll a, b and total and decreased stomatal conductance under stress in 41.1%. EBL treatments were able to maintain similar peroxidation levels between stressed and non-stressed plants. When analyzed together, these results indicate that EBL shows a promising perspective for improving rice tolerance to controlled water stress.
Com vistas à produção de alimentos saudáveis e livres de pesticidas, tem-se buscado fungicidas botânicos em plantas medicinais entre outras presentes no Bioma Cerrado. Os compostos biologicamente ativos destas ainda são pouco conhecidos, principalmente no controle de doenças em plantas. Desta forma, trabalho teve o objetivo de avaliar o potencial fungitóxico dos óleos essenciais de plantas do cerrado no controle dos fitopatógenos Curvularia lunata e Rhizoctonia solani. Foram realizadas coletas de plantas em regiões de cerrado para obtenção de extratos e óleos essenciais para testes in vitro, como formas de extrações foi utilizado metanol à frio para os extratos e para os óleos essenciais foi utilizado o equipamento clevenger. Foram avaliadas e identificadas um total de 28 famílias botânicas, sendo que a Asteraceae foi encontrada com maior frequência. Para a inibição do crescimento micelial de C. lunata e R. solani, o óleo essencial da Aristolochia holostylis, mostrou leve atividade fungistática, inibindo parcialmente o crescimento micelial. O óleo essencial da Xylopia frutescens, mostrou 100% de inibição do crescimento micelial dos fungos, nas concentrações de 50%, mostrando alto potencial fungitóxico.
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