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Abscisic acid (ABA) and 24-epibrassinolide regulate blossom-end rot (BER) development in tomato fruit under Ca2+ deficiency

Lucas Baiochi Riboldi, Sabrina Helena da Cruz Araújo, Julian Alejandro Giraldo Murcia, Sérgio Tonetto de Freitas, Paulo Roberto de Camargo e Castro .

Calcium (Ca2+) 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 Ca2+ 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 Ca2+ 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-1and 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, Ca2+ 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 Ca2+ contents in the fruits, when compared with the control. The highest fruit Ca2+ content was observed in plants treated with 0.01 µmol L-1 of EBL. According to our results, ABA and EBL increased Ca2+ concentrations and decreased BER incidence and thus there is a great potential for their use in agriculture in tomato fruit.

Cadmium toxicity degree on tomato development is associated with disbalances in B and Mn status at early stages of plant exposure

Marcia Eugenia Amaral Carvalho, Fernando Angelo Piotto, Mônica Regina Franco, Karina Lima Reis Borges, Salete Aparecida Gaziola, Paulo Roberto Camargo Castro, Ricardo Antunes Azevedo

Cadmium (Cd) toxicity is frequently coupled to its accumulation in plants, but not always the highest Cd concentration triggers the worst damages, indicating that additional events influence the magnitude of Cd side-effects. We investigated the early mechanisms behind the differential Cd-induced impacts on plant development of four tomato accessions with contrasting tolerance to Cd toxicity. At organ level, the highest Cd concentration was not associated with the largest biomass losses. In leaves, changes in superoxide dismutase and catalase activities were not related to differences in Cd concentration, which was unable to provoke H2O2 overproduction on the sixth day of plant exposure to this metal. Further investigation in the mineral profile revealed that magnitude of Cd toxicity depends probably on synergic effects from increased B status, in addition to the own Cd accumulation. Furthermore, disbalances in Mn status (i.e., excess in leaves and deficiency in roots) may enhance Cd toxicity degree. According to data, however, the low magnesium (Mg) status can be linked to tomato tolerance against Cd toxicity. In conclusion, the tomato tolerance degree under short-Cd exposure depends on actively, finely regulation of mineral homeostasis that results in different development of plant organs. The better understanding on the mode of action of Cd toxicity in plants can help in the establishment of strategies to mitigate its impacts on crop yield.

Is seaweed extract an elicitor compound? Changing proline content in drought-stressed bean plants

Marcia Eugenia Amaral Carvalho, Paulo Roberto de Camargo e Castro, Salete Aparecida Gaziola, Ricardo Aantunes Azevedo

Abiotic stresses negatively affect crop development and yield. However, the use of seaweed extracts can alleviate production losses through improvement of the antioxidant system and synthesis of compatible osmolytes. The aim of this study was to assess the effects of Ascophyllum nodosum extract on antioxidant response and yield of common bean plants (Phaseolus vulgaris) under drought stress. Therefore, two methods of application (foliar spray and soil irrigation) and two doses (5 and 10 mL L-1) were tested, whereas untreated plants were used as control. There were no significant differences in malondialdehyde and hydrogen peroxide contents among treatments, indicating that application of seaweed extract did not change the oxidative status in treated plants when compared to the control ones. On the other hand, the use of seaweed extract increased proline content even prior to drought stress (46.3 to 145.4% when compared to the control), and this increment remained until the 10th day of stress (from 60.1 to 201.7% over the reference plants), supporting early evidences that A. nodosum extract is a plant elicitor. The yield parameters were not affected by the extract, probably due to the severe drought stress which plants were submitted. The results suggest that A. nodosum extract affects proline metabolism in Phaseolus vulgaris plants, making the synthesis of this osmolyte more responsive to drought stress because seaweed-treated plants presented a higher proline content than the control ones during the exposure to water deficit.

'Spathaspora piracicabensis' f. a., sp. nov., a d-xylose-fermenting yeast species isolated from rotting wood in Brazil

Camila S. Varize, Raquel M. Cadete, Lucas D. Lopes, Renata M. Christofoleti-Furlan, Marc-Andre´ Lachance, Carlos A. Rosa, Luiz C. Basso

Two strains of a novel yeast species were isolated from rotting wood of an ornamental tree (purple quaresmeira, Tibouchina granulosa, Melastomataceae) in an Atlantic Rainforest area in Brazil. Analysis of the sequences of the internal transcribed spacer (ITS-5.8S) region and the D1/D2 domains of the large subunit rRNA gene showed that this species belongs to the Spathaspora clade, and is phylogenetically related to Spathaspora brasiliensis, Candida materiae and Sp. girioi. The novel species ferments D-xylose, producing ethanol, with amounts between 3.37 and 3.48 g L−1 ethanol from 2% d-xylose. Ascospores were not observed from this new species. The name Spathaspora piracicabensis f. a., sp. nov. is proposed to accommodate these isolates. The type strain is UFMG-CM-Y5867T (= CBS 15054T = ESALQ-I54T). The MycoBank number is MB 822,320.

Succession and toxicity of 'Microcystis' and 'Anabaena' ('Dolichospermum') blooms are controlled by nutrient-dependent allelopathic interactions

Mathias A. Chia, Jennifer G. Jankowiak, Benjamin J. Kramer, Jennifer A. Goleski, I-Shuo Huang, Paul V. Zimba, Maria do Carmo Bittencourt-Oliveira, Christopher J. Gobler

Microcystis and Anabaena (Dolichospermum) are among the most toxic cyanobacterial genera and often succeed each other during harmful algal blooms. The role allelopathy plays in the succession of these genera is not fully understood. The allelopathic interactions of six strains of Microcystis and Anabaena under different nutrient conditions in co-culture and in culture-filtrate experiments were investigated. Microcystis strains significantly reduced the growth of Anabaena strains in mixed cultures with direct cell-to-cell contact and high nutrient levels. Cell-free filtrate from Microcystis cultures proved equally potent in suppressing the growth of nutrient replete Anabaena cultures while also significantly reducing anatoxin-a production. Allelopathic interactions between Microcystis and Anabaena were, however, partly dependent on ambient nutrient levels. Anabaena dominated under low N conditions and Microcystis dominated under nutrient replete and low P during which allelochemicals caused the complete suppression of nitrogen fixation by Anabaena and stimulated glutathione S-transferase activity. The microcystin content of Microcystis was lowered with decreasing N and the presence of Anabaena decreased it further under low P and high nutrient conditions. Collectively, these results indicate that strong allelopathic interactions between Microcystis and Anabaena are closely intertwined with the availability of nutrients and that allelopathy may contribute to the succession, nitrogen availability, and toxicity of cyanobacterial blooms.

Effects of increased zooplankton biomass on phytoplankton and cyanotoxins: A tropical mesocosm study

Juliana dos Santos Severiano, Viviane Lúcia dos Santos Almeida-Melo, Maria do CarmoBittencourt-Oliveira, Mathias AhiiChia, Ariadne do Nascimento Moura

Zooplankton are important biocontrol agents for algal blooms in temperate lakes, while their potential in tropical and subtropical environments is not well understood. The aim of the present study was to evaluate the influence of increased zooplankton biomass on phytoplankton community and cyanotoxins (microcystins and saxitoxin) content of a tropical reservoir (Ipojuca reservoir, Brazil) using in situ mesocosms. Mesocosms consisted of 50 L transparent polyethylene bags suspended in the reservoir for twelve days. Phytoplankton populations were exposed to treatments having 1 (control), 2, 3 and 4 times the biomass of zooplankton found in the reservoir at the beginning of the experiment. Filamentous cyanobacteria such as Planktothrix agardhii and Cylindrospermopsis raciborskii were not negatively influenced by increasing zooplankton biomass. In contrast, the treatments with 3 and 4 times zooplankton biomass negatively affected the Cyanobacteria Aphanocapsa sp., Chroococcus sp., Dolichospermum sp., Merismopedia tenuissima, Microcystis aeruginosa and Pseudanabaena sp.; the diatom Cyclotella meneghiniana; and the cryptophyte Cryptomonas sp. Total microcystin concentration both increased and decreased at different times depending on zooplankton treatment, while saxitoxin level was not significantly different between the treatments and control. The results of the present study suggest that zooplankton biomass can be manipulated to control the excessive proliferation of non-filamentous bloom forming cyanobacteria (e.g. M. aeruginosa) and their associated cyanotoxins.

In vitro development of sugarcane seedlings using ethephon or gibberellin

Luciane de Siqueira Mendes, Marcia Eugenia Amaral Carvalho, Willian Rodrigues Macedo, Paulo Roberto de Camargo e Castro

The use of plant growth regulators is directly related to the success of in vitro propagation, which is an advantageous alternative to obtain seedlings on a commercial scale. This study aimed to evaluate the in vitro development of ‘IAC 95-5000’ sugarcane seedlings after the addition of different doses of ethephon (0, 25, 50, 100 and 200 mg L-1) or gibberellic acid (0, 2.5, 5.0, 7.5 and 10.0 mg L-1) to the culture medium. Ethephon increased the number of tillers (up to 231.70%), reduced height of the main tiller (44.66 to 60.47%), and did not affect the shoot´s fresh and dry mass. On the other hand, gibberellin decreased the number of tillers and negatively changed biomass partitioning. It is concluded that the use of ethephon is a potential strategy to enhance in vitro production of ‘IAC 95-5000’ sugarcane seedlings, since it increased the number of usable shoots in subsequent subcultures, and its effects on height reduction can be reversible. However, the use of the tested doses of gibberellic acid is not recommended, because it impaired seedling development of this sugarcane variety.

Secretory structures in Aldama species (Heliantheae–Asteraceae): morphology, histochemistry and composition of essential oils

Aline Bertolosi Bombo, Arinawa Liz Filartiga, Vera Lucia Garcia, Beatriz Appezzato-da-Glóriaa

Aldama representatives are particularly noteworthy for producing essential oils, and the chemical composition identification of these oils can help in the search for possible bioactive compounds, and provide useful information for taxonomic studies. A correct description of the occurrence and positioning of the secretory structures related to the production of these metabolites in the plant body could provide a basis for future studies on biological and pharmacological activity, indicating which organ merits further investigation. The four Aldama species investigated here were chosen due to their aromatic and resiniferous potential and because they are morphologically very similar. They were investigated phytochemically and their secretory structures were identified. Four types of secretory structures were found for the species herein: hydathodes, glandular trichomes, canals and cavities. Except for the hydathodes, all of them are responsible for the essential oil production. The highest yields of essential oils were obtained the underground organs. Seventy-nine compounds were identified for the four Aldama species, whereas 13 compounds occurred in the essential oils from all species and some of them were unique to a given species. The chemical composition of the four species, described herein for the first time, can be used for identification purposes and, also reveals several compounds of proven biological activity, confirming the potential usefulness of Aldama species.

Underground organs of Brazilian Asteraceae: testing the CLO-PLA database traits

Arinawa Liz Filartiga; Jitka Klimešová; Beatriz Appezzato-da-Glória

Not all plant traits from all regions have been standardized or databased. Some ecosystems, such as tropical grasslands, are under-represented in such databases owing to the difficulty in assessing bud banks and evaluating clonal growth. This study aimed to (i) determine whether Brazilian morphological traits of belowground organs can be translated into categories used in the CLO-PLA database and (ii) assess the applicability of clonal and bud bank traits standardized in the CLO-PLA database for Brazilian Aldama species, which have specialized belowground organs and are able to resprout. In all, 165 species, including herbs, subshrubs and shrubs, of 37 genera from different Brazilian ecosystems, were evaluated. Not all the traditional Brazilian morphological categories could be translated into CLO-PLA traits, resulting in a lower number of categories and loss of information regarding plant morphology. Furthermore, clonal and bud bank traits could be only partially evaluated for Aldama, since some traits showed seasonal variation. The CLO-PLA classification focused on the organs in relation to the soil surface, the connection between mother and daughter shoots, and the origin of buds from which daughter shoots sprout. In the Brazilian classification, by contrast, anatomical features or early ontogeny of the organ are very important. Nevertheless, our results might form the basis for future comparative studies across ecosystems and biomes, for which common trait standardization is necessary. However, further research is needed to assess the functional morphology of clonal and bud bank traits in tropical regions.

Sugarcane smut: shedding light on the development of the whip-shaped sorus

João Paulo R. Marques, Beatriz Appezzato-da-Glória, Meike Piepenbring, Nelson S. Massola Jr., Claudia B. Monteiro-Vitorello, Maria Lucia Carneiro Vieira

Background and Aims Sugarcane smut is caused by the fungus Sporisorium scitamineum (Ustilaginales/Ustilaginomycotina/Basidiomycota), which is responsible for losses in sugarcane production worldwide. Infected plants show a profound metabolic modification resulting in the development of a whip-shaped structure (sorus) composed of a mixture of plant tissues and fungal hyphae. Within this structure, ustilospores develop and disseminate the disease. Despite the importance of this disease, a detailed histopathological analysis of the plant–pathogen interaction is lacking.