M. Carmen Antolín

Thermotolerance responses in ripening berries of Vitis vinifera L. cv Muscat Hamburg

Berry organoleptic properties are highly influenced by ripening environmental conditions. In this study, we used grapevine fruiting cuttings to follow berry ripening under different controlled conditions of temperature and irradiation intensity. Berries ripened at higher temperatures showed reduced anthocyanin accumulation and hastened ripening, leading to a characteristic drop in malic acid and total acidity. The GrapeGen GeneChip® combined with a newly developed GrapeGen 12Xv1 MapMan version were utilized for the functional analysis of berry transcriptomic differences after 2 week treatments from veraison onset. These analyses revealed the establishment of a thermotolerance response in berries under high temperatures marked by the induction of heat shock protein (HSP) chaperones and the repression of transmembrane transporter-encoding transcripts. The thermotolerance response was coincident with up-regulation of ERF subfamily transcription factors and increased ABA levels, suggesting their participation in the maintenance of the acclimation response. Lower expression of amino acid transporter-encoding transcripts at high temperature correlated with balanced amino acid content, suggesting a transcriptional compensation of temperature effects on protein and membrane stability to allow for completion of berry ripening. In contrast, the lower accumulation of anthocyanins and higher malate metabolization measured under high temperature might partly result from imbalance in the expression and function of their specific transmembrane transporters and expression changes in genes involved in their metabolic pathways. These results open up new views to improve our understanding of berry ripening under high temperatures.

Plant availability of heavy metals in a soil amended with a high dose of sewage sludge under drought conditions

The objective of this research was to study the effect of water deficit on soil heavy metal availability and metal uptake by ryegrass (Lolium multiflorum Lam.) plants grown in a soil amended with a high dose of rural sewage sludge. Three fertility treatments were applied: sewage sludge (SS), mineral fertilizer (M), and control (C); unamended). The levels of irrigation were: well-watered (W) and water deficit (D). Microbial respiration decreased the total organic C (TOC) in sludge-treated soils, but this did not enhance soil DTPA-extractable heavy metal concentrations. Indeed, Zn, Cu, Mn and Ni availability decreased during the experiment. C- and M-treated soils showed either no changes or increases of some trace element concentrations during the incubation. In the plant experiment, ryegrass dry matter (DM) yield, relative water content (RWC) and leaf water potential (Ψw) decreased in drought conditions. Sludge addition increased metal concentrations in plants. However, in some instances, SS-treated plants showed either similar or lower transfer coefficient (Tc) values than did plants in the C and M treatments. Water deficit decreased the concentration and the Tc of some metals in roots of M and SS plants. Results indicate that sludge-borne heavy metals were maintained in chemical forms of low availability. The lower metal uptake by SS and M plants under dry conditions cannot be attributed to a lower availability of these elements in soil.

Relationship between photosynthetic capacity, nitrogen assimilation and nodule metabolism in alfalfa (Medicago sativa) grown with sewage sludge.

Sewage sludge has been used as N fertilizer because it contains some of inorganic N, principally as nitrate and ammonium ions. However, sewage sludge addition to legumes could result in impaired nodule metabolism due to the presence of inorganic N from sludge. A greenhouse experiment was conducted to examine the effects of sewage sludge on growth, photosynthesis, nitrogen assimilation and nodule metabolism in alfalfa (Medicago sativa L. cv. Aragón). Plants were grown in pots with a mixture of perlite and vermiculite (2:1, v/v). The experiment included three treatments: (1) plants inoculated with rhizobia and amended with sewage sludge at rate of 10% (w/w) (RS); (2) plants inoculated with rhizobia without any amendment (R); and (3) non-inoculated plants fed with ammonium nitrate (N). N(2)-fixing plants had lower growth and sucrose phosphate synthase activity but higher photosynthesis than nitrate-fed plants because they compensated the carbon cost of the rhizobia. However, sewage sludge-treated plants evidenced a loss of carbon sink strength due to N(2) fixation by means of decreased photosynthetic capacity, leaf chlorophylls and N concentration in comparison to untreated plants. Sewage sludge did no affect nodulation but decreased nodule enzyme activities involved in carbon and N metabolisms that may lead to accumulation of toxic N-compounds.

Grapevine Fruiting Cuttings: An Experimental System to Study Grapevine Physiology Under Water Deficit Conditions

Partial rootzone drying (PRD) is an irrigation system that may improve the water use efficiency of crop production by means of better control of vegetative growth without reducing fruit yield (Kang and Zhang 2004). PRD uses biochemical response of plants to water stress to achieve a balance between vegetative and reproductive development (Davies and Hartung 2004). However, the underlying nature of how PRD affects berry ripening is only poorly defined, as indicated by the considerable controversy in the literature (Du Toit et al. 2003, Santos et al. 2003, Gu et al. 2004). This may be due to either poor implementation of PRD, or the interaction of many factors on grapevine growth and reproductive development. Given such ambiguities, it becomes necessary to design a PRD system that permits a fine control of most environmental factors with the aim to know the nature of PRD response of plants. Therefore, we have developed a method which uses fruiting cuttings subjected to PRD irrigation under controlled conditions. Emphasis is placed on physiological aspects including berry hormonal balance related to long-distance chemical signalling induced by soil drying.

Effects of Water-Deficit Irrigation on Hormonal Content and Nitrogen Compounds in Developing Berries of Vitis vinifera L. cv. Tempranillo

Water-deficit irrigation to grapevines reduces plant growth, yield, and berry growth, altering the ripening process, all of which may influence fruit composition and wine quality. Therefore, the goals of this study were (1) to investigate the influence of the main endogenous berry hormones, abscisic acid (ABA), indole-3-acetic acid (IAA), salicylic acid (SA), and jasmonic acid (JA), on berry growth and ripening under water-deficit conditions and (2) to analyze changes in fruit composition, specifically N compounds, under water deprivation. The study was carried out using container-grown Tempranillo grapevines grown under controlled conditions in a greenhouse. Two irrigation treatments were imposed: control (well-watered) and sustained deficit irrigation (SDI). Water deficit decreased leaf area and the source-to-sink ratio, reduced yield and berry size, and decreased concentrations of the main phenolic compounds. SDI also modified berry hormonal status. At the pea-size stage, SDI berries had lower IAA and higher JA and SA than nonstressed berries. At veraison (onset of ripening), accumulation of ABA was less accentuated in SDI than in control berries. At harvest, the content of amino acids and free ammonium was low in both treatments but SDI-treated berries showed a significant accumulation of amines. Results suggest that water restrictions to grapevines might be playing a physiological role in reducing berry growth through affecting hormone dynamics, phenolic synthesis, and the berry amino acid content and composition, which could compromise fruit quality. Possible roles of endogenous IAA controlling berry size and endogenous ABA and SA controlling levels of anthocyanins and flavonols at harvest are discussed.

Berry quality and antioxidant properties in Vitis vinifera cv. Tempranillo as affected by clonal variability, mycorrhizal inoculation and temperature

Abstract. The projected increase in mean temperatures caused by climate change is expected to have detrimental impacts on berry quality. Microorganisms as arbuscular mycorrhizal fungi (AMF) produce numerous benefits to host plants and can help plants to cope with abiotic stresses such as high temperature. The aims of this research were to characterise the response of three clones of Vitis vinifera L. cv. Tempranillo to elevated temperatures and to determine whether AMF inoculation can improve berry antioxidant properties under these conditions. The study was carried out on three fruit-bearing cuttings clones of cv. Tempranillo (CL-260, CL-1048 and CL-1089) inoculated with AMF or uninoculated and subjected to two temperature regimes (day–night: 24°C−14°C and 28°C−18°C) during berry ripening. Results showed that clonal diversity of Tempranillo resulted in different abilities to respond to elevated temperature and AMF inoculation. In CL-1048, AMF inoculation improved parameters related to phenolic maturity such as anthocyanin content and increased antioxidant activity under elevated temperature, demonstrating a protective role of AMF inoculation against warming effects on berry quality. The results therefore suggest that selection of new clones and/or the implementation of measures to promote the association of grapevines with AMF could be strategies to improve berry antioxidant properties under future warming conditions.

Sewage sludge application can induce changes in antioxidant status of nodulated alfalfa plants.

A greenhouse experiment was conducted to investigate the oxidative stress produced by sewage sludge addition on nodulated alfalfa (Medicago sativa L. cv. Aragón) plants. Two types of sludge were incorporated into substrate: anaerobic mesophilic digested (AM) and autothermal thermophilic aerobic digested (ATAD) sludge. Pots without sludge but with inoculated plants were used as control treatment for comparison. Results showed that sludge amended plants had increased tissue accumulation of heavy metals that induced oxidative stress. This is characterized by induction of the antioxidant enzymatic activities and alterations in the redox state of ascorbate. ATAD sludge application produced a reduction in nodulation, increased nodule antioxidant enzyme activities and decreased ascorbate/dehydroascorbate ratio. As a consequence, nodules of ATAD treatment suffered from oxidative damages as evidenced by high malondialdehyde levels. By contrast, AM application enhanced plant growth and no deleterious effects on nodulation were found. Nodules developed in AM sludge had increased antioxidant enzyme activities, ascorbate/dehydroascorbate ratio and improved capacity for thiol synthesis. Results clearly showed that nodulated alfalfa performed better in AM than in ATAD sludge and suggest that differential response appears to be mediated by plant ability to thiol synthesis and to maintenance of a more equilibrated antioxidant status.

Arbuscular mycorrhizal symbiosis as a promising resource for Improving berry quality in grapevines under changing environments

Climate change and their resulting impacts are becoming a concern for winegrowers due to the high socioeconomic relevance of the winemaking sector worldwide. In fact, the projected climate change is expected to have detrimental impacts on the yield of grapevines, as well as on the quality and properties of grapes and wine. It is well known that arbuscular mycorrhizal fungi (AMF) can improve the nutritional quality of edible parts of crops and play essential roles in the maintenance of host plant fitness under stressed environments, including grapevines. The future scenarios of climate change may also modify the diversity and the growth of AMF in soils as well as the functionality of the mycorrhizal symbiosis. In this review, we summarize recent research progress on the effects of climate change on grapevine metabolism, paying special attention to the secondary compounds involved in the organoleptic properties of grapes and wines and to the levels of the phytohormones implied in the control of berry development and fruit ripening. In this context, the potential role of AMF for maintaining fruit quality in future climate change scenarios is discussed.

Nutritional properties of Tempranillo grapevine leaves are affected by clonal diversity, mycorrhizal symbiosis and air temperature regime

Tempranillo grapevine is widely cultivated in Spain and other countries over the world (Portugal, USA, France, Australia, and Argentina, among others) for its wine, but leaves are scarcely used for human or animal nutrition. Since high temperatures affect quality of fruits and leaves in grapevine and the association of Tempranillo with arbuscular mycorrhizal fungi (AMF) enhances the antioxidant properties of berries and leaves, we assessed the effect of elevated air temperature and mycorrhization, separately or combined, on the nutritional properties of Tempranillo leaves at the time of fruit harvest. Experimental assay included three clones (CL-260, CL-1048, and CL-1089) and two temperature regimes (24/14 °C or 28/18 °C day/night) during fruit ripening. Within each clone and temperature regime there were plants not inoculated or inoculated with AMF. The nutritional value of leaves increased under warming climate: elevated temperatures induced the accumulation of minerals, especially in CL-1089; antioxidant capacity and soluble sugars also increased in CL-1089; CL-260 showed enhanced amounts of pigments, and chlorophylls and soluble proteins increased in CL-1048. Results suggested the possibility of collecting leaves together with fruit harvest with different applications of every clone: those from CL-1089 would be adequate for an energetic diet and leaves from CL-260 and CL-1048 would be suitable for culinary processes. Mycorrhization improved the nutritional value of leaves by enhancing flavonols in all clones, hydroxycinnamic acids in CL-1089 and carotenoids in CL-260.