Previous studies have demonstrated that moderate water restrictions and enhanced CO2 concentration can maintain or improve yield and accumulation of secondary compounds in lettuce under greenhouse conditions. Therefore, the aim of this study was to evaluate the combination of reduced soil moisture and carbon fertilization in shoot fresh weight (FW) and antioxidant capacity of two Batavia lettuce cultivars (Batabia Rubia Munguia; BRM and Maravilla de Verano; MV). Moderate water restriction treatment was equivalent to 2/3 of the field capacity and elevated CO2 concentration (ECO2) was fixed at similar to 700 mu mol mol(-1). While CO2 enrichment exerted a positive effect on shoot FW of MV, especially in combination with water restrictions, the yield of the cultivar BRM was not affected by CO2 concentration, nor by irrigation regime. However, antioxidant capacity of BRM plants was increased under ECO2 conditions. These results demonstrate that carbon fertilization and/or moderate water limitations can be strategically used to enhance nutritional value and growth of greenhouse lettuce.

Elevated concentrations of CO2 (CO2) in plants with C-3 photosynthesis metabolism, such as wheat, stimulate photosynthetic rates. However, photosynthesis tends to decrease as a function of exposure to high (CO2) due to down-regulation of the photosynthetic machinery, and this phenomenon is defined as photosynthetic acclimation. Considerable efforts are currently done to determine the effect of photosynthetic tissues, such us spike, in grain filling. There is good evidence that the contribution of ears to grain filling may be important not only under good agronomic conditions but also under high (CO2). The main objective of this study was to compare photoassimilate production and energy metabolism between flag leaves and glumes as part of ears of wheat (Triticum turgidum L. subsp. durum cv. Amilcar) plants exposed to ambient [a(CO2)] and elevated [e(CO2)] (CO2) (400 and 700 mu mol mol(-1), respectively). Elevated CO2 had a differential effect on the responses of flag leaves and ears. The ears showed higher gross photosynthesis and respiration rates compared to the flag leaves. The higher ear carbohydrate content and respiration rates contribute to increase the grain dry mass. Our results support the concept that acclimation of photosynthesis to e(CO2) is driven by sugar accumulation, reduction in N concentrations and repression of genes related to photosynthesis, glycolysis and the tricarboxylic acid cycle, and that these were more marked in glumes than leaves. Further, important differences are described on responsiveness of flag leaves and ears to e(CO2) on genes linked with carbon and nitrogen metabolism. These findings provide information about the impact of e(CO2) on ear development during the grain filling stage and are significant for understanding the effects of increasing (CO2) on crop yield.

The exploitation of genetic diversity within agricultural plants, including grapevine, is suggested as a valuable tool to cope with the negative impacts of climate change on yield and crop quality. In some winegrowing regions of Europe, there is a renewed interest in knowing the grapevine genetic resources available, focusing on the prospection, recovery, and study of ancient cultivars typical of every zone. Grapevines are naturally associated with arbuscular mycorrhizal fungi (AMF), which provide some benefits to the host plant, although such effects depending on many factors, including variety. Therefore, the aim of this research was to characterize the potential fruit quality of eight old grapevine varieties recovered in Navarre (northeastern of the Iberian Peninsula), associated or not with AMF. The study was carried out on fruit-bearing cuttings grown under controlled conditions (greenhouse). Overall, AMF inoculation reduced bunch and berry mass, as well as phenolic content in fruits. In some varieties, AMF association improved some berry traits by increasing the concentrations of soluble solids and anthocyanins; in others, berry colour, total phenolic and anthocyanin content were diminished in AMF-inoculated plants. The results, therefore, suggest that intraspecific diversity of old grapevines could include different abilities to respond to arbuscular mycorrhizal symbiosis.

The association that many crops can establish with the arbuscular mycorrhizal fungi (AMF) present in soils can enhance the resistance of the host plants against several pathogens, including Verticillium spp. The increased resistance of mycorrhizal plants is mainly due to the improved nutritional and water status of crops and to enhanced antioxidant metabolism and/or increased production of secondary metabolites in the plant tissues. However, the effectiveness of AMF in protecting their host plants against Verticillium spp. may vary depending on the environmental factors. Some environmental factors, such as the concentration of carbon dioxide in the atmosphere, the availability of soil water and the air and soil temperatures, are predicted to change drastically by the end of the century. The present paper discusses to what extent the climate change may influence the role of AMF in protecting crops against Verticillium-induced wilt, taking into account the current knowledge about the direct and indirect effects that the changing environment can exert on AMF communities in soils and on the symbiosis between crops and AMF, as well as on the development, incidence and impact of diseases caused by soil-borne pathogens.

Over the last decades, tillage, chemical fertilizers, and pesticides have reduced the beneficial fungal population size in arable soils. Though soil inoculation can be a practical way to restore arbuscular mycorrhizal fungi (AMF) population size, weeds may also be benefited, as well. This study was aimed to evaluate the effect of three AMF species (Funneliformis mosseae, Rhizoglomus fasciculatum, andRhizoglomus intraradices) on photosynthetic rate, secondary metabolites content, reproductive organs percentage and nutrient uptake inSolanum nigrumL. andDigitaria sanguinalisL. weed species.Our results showed species variation in response to AMF inoculation, so that, while inoculation withR. intraradicesfungal species decreased total biomass inS. nigrumplants significantly, it increased total biomass ofD. sanguinalisplants by 26-49%. In addition, inoculation withF. mosseaespecies increased phenol, anthocyanin, and total terpenoid content inS. nigrumplants much more thanD. sanguinalis. Increased photosynthetic rate, secondary metabolites content, and flowering percentage in AMF-inoculatedS. nigrumplants show the enhanced competitive ability and allelopathic potential of this weed when associated with AMF, which makes it a good competitor against other plant species in the environment.

(1) Background: Vitis vinifera L. cv. Tempranillo is cultivated over the world for its wine of high quality. The association of Tempranillo with arbuscular mycorrhizal fungi (AMF) induced the accumulation of phenolics and carotenoids in leaves, affected the metabolism of abscisic acid (ABA) during berry ripening, and modulated some characteristics and quality aspects of grapes. The objective of this study was to elucidate if AMF influenced the profiles and the content of primary and secondary metabolites determinants for berry quality in Tempranillo. (2) Methods: Fruit-bearing cuttings inoculated with AMF or uninoculated were cultivated under controlled conditions. (3) Results: Mycorrhizal symbiosis modified the profile of metabolites in Tempranillo berries, especially those of the primary compounds. The levels of glucose and amino acids clearly increased in berries of mycorrhized Tempranillo grapevines, including those of the aromatic precursor amino acids. However, mycorrhizal inoculation barely influenced the total amount and the profiles of anthocyanins and flavonols in berries. (4) Conclusions: Mycorrhizal inoculation of Tempranillo grapevines may be an alternative to the exogenous application of nitrogen compounds in order to enhance the contents of amino acids in grapes, which may affect the aromatic characteristics of wines.

Grapevine leaves are widely discarded in open fields despite their known antioxidant properties. We tested the cytotoxicity of leaf extracts from three clones (CL-260, CL-1048, CL-8) of Vitis vinifera L. cv. Tempranillo against four human cancer cell lines: colon, HT-29; breast, MCF-7; lung HTB-54; and lymphoblastic leukemia, CCRF-CEM. Grapevines were cultivated at either ambient (24/14 degrees C) or elevated (28/18 degrees C) day/night temperatures, and inoculated (+M) or not (-M) with arbuscular mycorrhizal fungi (AMF). Cytotoxicity was analysed by MTT assays. Elevated air temperatures enhanced the cytotoxicity of leaf extracts from CL-260 against HT-29, CCRF-CEM and HTB-54 and that from CL-8 against MCF-7. Mycorrhization improved the cytotoxicity of leaf extracts from CL-1048 against HT-29, CCRF-CEM, HTB-54 and MCF-7. The cytotoxic activities of CL-260 against HTB-54 and CL-1048 against HT-29 were correlated, respectively, with total phenols and total antioxidant capacity. We conclude that the predicted increase in air temperature for the future climate and the mycorrhizal association of grapevines may enhance the cytotoxicity of leaves, which strengthens the potential application of these agricultural residuals for biomedicine. However, the clonal diversity in the response to AMF and air temperature highlights the importance of choosing the most adequate clone for a concrete environmental scenario.

The projected climate scenario for South Mediterranean Europe predicts lower precipitation and higher temperatures that will negatively affect viticulture in the region. The application of moderate deficit irrigation at crucial moments of berry ripening has been found to improve berry quality. Furthermore, grapevine association with arbuscular mycorrhizal fungi (AMF) may improve grapevine¿s ability to cope with abiotic stresses. Therefore, the aims of this research were: (1) to characterize the response of three clones of Vitis vinifera L. cv. Tempranillo to the combination of different water deficit programs and AMF inoculation under elevated temperatures, and (2) 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-1089 and CL-843) inoculated (+M) or not (¿M) with AMF and subjected to two temperature regimes (24/14 °C and 28/18 °C (day/night)) combined with three irrigation regimes during berry ripening. Irrigation treatments were: (i) water deficit from fruit set to veraison (early deficit, ED); (ii) water deficit from veraison to maturity (late deficit, LD); and (iii) full irrigation (FI). Although each Tempranillo clone seemed to have different abilities to respond to elevated temperatures and water supply, in general, at 24/14 °C the LD treatment performed better than ED. Differences among clones were attenuated at 28/18 °C...

Arbuscular mycorrhizal symbiosis is a promising tool for improving the quality of grapes under changing environments. Therefore, the aim of this research was to determine if the ability of arbuscular mycorrhizal fungi (AMF) to enhance phenolic content (specifically, anthocyanins) in a climate change framework could be mediated by alterations in berry ABA metabolism during ripening. The study was carried out on fruit-bearing cuttings of cv. Tempranillo (CL-1048 and CL-1089) inoculated (+M) or not (¿M) with AMF. Two experimental designs were implemented. In the first experiment +M and -M plants were subjected to two temperatures (24/14¿°C or 28/18¿°C (day/night)) from fruit set to berry maturity. In the second experiment, +M and -M plants were subjected to two temperatures (24/14¿°C or 28/18¿°C (day/night)) combined with two irrigation regimes (late water deficit (LD) and full irrigation (FI)). At 28/18¿°C AMF contributed to an increase in berry anthocyanins and modulated ABA metabolism, leading to higher ABA-GE and 7¿OH-ABA and lower phaseic acid (PA) in berries compared to ¿M plants. Under the most stressful scenario (LD and 28/18¿°C), at harvest +M plants exhibited higher berry anthocyanins and 7¿OH-ABA and lower PA and dihydrophaseic acid (DPA) levels than ¿M plants. These findings highlight the involvement of ABA metabolism into the ability of AMF to improve some traits involved in the quality of grapes under global warming scenarios.

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.

Throughout the southern Mediterranean regions of Europe, projected climate warming combined with severe droughts during the growing season may alter grape metabolism, thus modifying the nutritional value of berries and the quality of wines. This study investigated the effects of pre- and post-veraison drought under elevated temperatures on berry skin metabolism of two Tempranillo clones (CL). Experimental assays were performed on fruit-bearing cuttings from CL-1089 and CL-843 of Vitis vinifera (L.) cv. Tempranillo subjected to two temperature regimes (24/14 °C or 28/18 °C (day/night)) combined with three irrigation regimes during berry ripening: (i) water deficit from fruit set to veraison (early deficit, ED); (ii) water deficit from veraison to maturity (late deficit, LD); and (iii) full irrigation (FI). At 24/14 °C, the LD treatment performed better than the ED treatment. Differences were attenuated at 28/18 °C and responses were modulated by type of clone. Elevated temperatures induced the accumulation of hexoses and amino acids in berries. ED at 24/14 °C reduced anthocyanins and flavonols, which may decrease the antioxidant properties of fruits. In contrast, the levels of these secondary metabolites did not decrease when LD was applied. Our results suggest that the adaptation of grapevines for climate change might be plausible with the optimization of timing of water deficit and the appropriate selection of clones.

Modern agriculture and horticulture must combine two objectives that seem to be almost mutually exclusive: to satisfy the nutritional needs of an increasing human population and to minimize the negative impact on the environment. These two objectives are included in the Goal 2 of the 2030 Agenda for Sustainable Development of the United Nations: End hunger, achieve food security and improved nutrition and promote sustainable agriculture'. Enhancing the nutritional levels of vegetables would improve nutrient intake without requiring an increase in consumption. In this context, the use of beneficial rhizospheric microorganisms for improving, not only growth and yield, but also the nutrient quality of crops represents a promising tool that may respond to the challenges for modern agriculture and horticulture and represents an alternative to the genetic engineering of crops. This paper summarizes the state of the art, the current difficulties associated to the use of rhizospheric microorganisms as enhancers of the nutritional quality of food crops as well as the future prospects.

Las previsiones sobre el aumento de temperatura debido al cambio climático indican que éste repercutirá negativamente sobre la calidad de la uva. Sin embargo, ciertos microorganismos como los hongos micorrícicos arbusculares (HMA) pueden producir numerosos beneficios en la planta hospedadora que incluyen una mayor tolerancia a los estreses ambientales, tales como la temperatura elevada. Por tanto, los objetivos de este estudio han sido caracterizar la respuesta de tres clones de Tempranillo al aumento de la temperatura y determinar si la inoculación con HMA puede mejorar las propiedades antioxidantes de la baya bajo esas condiciones. El estudio se llevó a cabo con esquejes fructíferos de Tempranillo inoculados o no con HMA y sometidos a dos regímenes de temperatura (24/14 °C y 28/18 °C (día/noche)). Los resultados muestran que cada uno de los clones respondió de diferente forma a la temperatura y a la inoculación micorrícica lo que sugiere que la selección de nuevos clones y/o la implementación de medidas para promover la asociación de la vid con HMA podrían ser estrategias adecuadas para mejorar las propiedades antioxidantes de la vid ante las futuras condiciones climáticas.

The combined application of humic substances and mycorrhizal inocula under increased CO2 in the air is a promising horticultural technique for improving the quality of greenhouse-grown onion seedlings. The objective of this study was to evaluate if the development and qualitative characteristics of bulbs from the yellow onion Allium cepa L. Alfa São Francisco improved with the application of the abovementioned agronomic, biotic, and environmental factors. The lowest dry matter was achieved in bulbs of onions not inoculated with mycorrhizal fungi, non-amended with humic acids (HA), and grown at ambient CO2. Mycorrhizal inoculation significantly increased bulb biomass in plants cultivated at ambient CO2, and not fertilized with HA, which may be a consequence of the enhanced acid phosphatase activity in roots. The application of HA always increased bulb dry matter, which were more evident at elevated rather than ambient CO2 conditions and correlated with improved acid phosphatase activity in the plants at elevated CO2. Mycorrhizal inoculation, HA supplementation, and elevated CO2 in the air had an additive effect of increasing the content of soluble sugars, proteins, and phenolics in bulbs. While high levels of sugars and proteins enhanced the energetic value of onions, the increase in phenolics improved their antioxidant properties. The triple interaction between mycorrhization, HA fertilization, and elevated CO2 also increased the ratio between soluble solids and total titratable acidity, which may enhance the perception of sweetness and make onions more pleasant for consumption.

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.

Predicted reduced precipitation, enhanced evaporative demand and increasing CO2 in the atmosphere will strongly influence wheat production. The association of wheat with arbuscular mycorrhizal fungi (AMF) improves growth under stressful conditions. Our objective was to test the influence of mycorrhizal inoculation on yield, and accumulation of macro- and micro-nutrients and gliadins in grains of durum wheat (Triticum durum Desf.) plants grown under different CO2 concentrations and water regimes. The main factors of the experimental design were mycorrhizal inoculation (inoculated or non-inoculated plants); atmospheric CO2 concentration (ambient, ACO2, or elevated, ECO2); and water regime (optimal or restricted water regime). At ACO2, the simultaneous application of AMF and water deficit decreased the number of seeds per spike without affecting the biomass of grains, and grains accumulated higher contents of copper, iron, manganese, zinc and gliadins. The opposite effect was observed with ECO2 where, regardless of mycorrhizal and water treatment factors, a general depletion of contents of micro- and macro-nutrients and gliadins was detected. Whereas mycorrhizal inoculation together with drought applied to plants cultivated at ACO2 improved wheat grain quality parameters, under ECO2, mycorrhization did not ameliorate grain quality parameters detected in plants that produced the largest grain dry matter values.

This paper describes the use of fruit-bearing grapevine hardwood cuttings as a model system for grapevine research, translating some studies that are difficult to execute under field conditions in the vineyards to facilities under controlled conditions. This approach enables to simulate in greenhouses future climate conditions and to investigate putative responses of grapevine to climate change. An updated description of how to grow grapevine fruit-bearing cuttings is made, together with modifications to carry out studies of partial rootzone drying, regulated deficit irrigation studies and symbiosis with arbuscular mycorrhizal fungi. We summarize how extensive has been the use of fruit-bearing cuttings in grapevine research over the years, with special emphasis in those experiments that analyze the effects of factors related to climate change, such as elevated CO2, elevated temperature, water availability and UV-B radiation, on grapevine physiology, production and grape quality. A validation of the model is made, comparing results obtained with fruit-bearing cuttings with those obtained from vineyard-grown plants. We discuss some advantages of growing grapevines under elevated CO2 with an atmosphere depleted in C-13, using this stable isotope (C-13) and others (N-15, Fe-54 or Fe-57, etc.) as tracers for C, N and other nutrient metabolism studies.

The effect of mycorrhizal inoculation and/or selenium (Se) application as possible agents to improve post-harvest performance of cut snapdragon (Antirrhinum majus L.) flowers had been studied. Rhizophagus intraradices was inoculated to half of plants at the seedling stage. One third of non-inoculated plants and one third of plants inoculated with R. intraradices were not supplied with Se. One third of non-inoculated and inoculated plants were foliar-sprayed with either 100 or 200 ¿g of seleninic acid per plant before flowering. Flowers were harvested at dawn, packed dry or placed in water and stored in darkness at 5 °C. Afterwards, the vase-life of cut flowers was evaluated. Plant growth and water parameters as well as photosynthetic pigments and organic solutes in leaves were determined at harvesting. The results showed that mycorrhizal inoculation improved plant height, length and basal diameter of flowering stems. In plants untreated with Se, mycorrhizal inoculation increased starch, phenolics, chlorophylls and carotenoids but decreased soluble sugars and proline in leaves. Mycorrhizal inoculation counteracted the reductions in carbohydrates, proline and proteins caused by Se in non-inoculated plants. Type of storage strongly influenced post-harvest performance of cut flowers, being dry storage the most beneficial for delaying senescence. In comparison with non-inoculated plants untreated with Se, neither mycorrhizal inoculation nor the foliar application of Se, alone or combined, prolonged the vase-life of cut flowers. High dose of Se decreased the vase-life of flowers from non-inoculated snapdragons and mycorrhizal inoculation counteracted this negative effect. Changes in water status and carbohydrate metabolism in plants inoculated or not with R. intraradices may have resulted in unusual development of flowering stems and post-harvest performance of flowers after spraying high dose of Se. Further research is needed to confirm this hypothesis.

Fertilization with humic substances (HS) has been proposed as target tool to improve crop production within a sustainable agriculture framework. The dose and application method are two factors that can influence the effect of HS on nutrient composition and productivity of onion. Therefore, our main objective was to assess the effect of each of the abovementioned factors, separately or interacting, on the quality and productivity of onion bulbs in a field test. The experimental design was completely randomized in a factorial 2 x 3, with two methods of application of HS and three different doses. The combined application method, immersion together with foliar pulverization, showed highest improvement of biomass and nutritional content of bulbs. However, while the intermediate dose of HS exerted greater increases on onion yield, productivity, carbohydrates and proteins levels in bulbs, mineral nutrient accumulation resulted especially when highest doses of HS were added. From a nutritional point of view, higher sweetness (from 113 to 149 mg g(-1) of soluble sugars in dry matter) and an improved P, K and Mg content of bulbs (4.00, 11.65 and 3.18 g kg(-1), respectively) in response to HS addition has been ascribed.

Within climate change scenario, the maintenance of grape quality and wine characteristics will be the main concern for viticulture in the future years. However, changes in the composition of grapevine pruning wastes (i.e., leaves and stems) could be another interesting aspect as important antioxidant source for pharmaceutical industry due its richness in phenolic compounds beneficial for human health. To date, the effect of biotic and environmental factors in the accumulation of these compounds in leaves had received little attention. Therefore, the aims of study were (1) to evaluate the effect of biotic (mycorrhizal inoculation) and environmental (temperature) factors, alone or combined, on phenolic composition and antioxidant activity of leaf extracts of grapevine and (2) to determine whether such effects differed among accessions of the same cultivar of grapevine. The study was carried out using container-grown grapevines grown in greenhouses. Dormant Vitis vinifera (L.) cuttings of different accessions of Tempranillo were selected to get fruit-bearing cuttings. At transplanting, half of the plants of each accession were inoculated with the mycorrhizal inoculum and after fruit set, plants were exposed to two temperature regimes (24. °C/14. °C and 28. °C/18. °C (day/night)) to commercially berry ripe. Results showed that total phenolic content, antioxidant compounds like flavonols and anthocyanins, and antioxidant activity of leaves were improved with mycorrhizal inoculation under high temperature conditions. It was concluded that mycorrhizal inoculation of grapevines could contribute to preserve high level of antioxidant compounds of leaves in a future climate change scenario. However, the effects were strongly dependent of accession assayed, which indicated a significant intra-varietal diversity in the response of Tempranillo to biotic and environmental factors.

Pearl millet (Pennisetum glaucum L.) is an important fodder and is a potential feedstock for fuel ethanol production in dry areas. Our objectives were to assess the effect of elevated CO2 and/or reduced irrigation on biomass production and levels of sugars and proteins in leaves of pearl millet and to test whether mycorrhizal inoculation could modulate the effects of these abiotic factors on growth and metabolism. Results showed that mycorrhizal inoculation and water regime most influenced biomass of shoots and roots; however, their individual effects were dependent on the atmospheric CO2 concentration. At ambient CO2, mycorrhizal inoculation helped to alleviate effects of water deficit on pearl millet without significant decreases in biomass production, which contrasted with the low biomass of mycorrhizal plants under restricted irrigation and elevated CO2. Mycorrhizal inoculation enhanced water content in shoots, whereas reduced irrigation decreased water content in roots. The triple interaction between CO2, arbuscular mycorrhizal fungi (AMF) and water regime significantly affected the total amount of soluble sugars and determined the predominant soluble sugars in leaves. Under optimal irrigation, elevated CO2 increased the proportion of hexoses in pearl millet that was not inoculated with AMF, thus improving the quality of this plant material for bioethanol production. By contrast, elevated CO2 decreased the levels of proteins in leaves, thus limiting the quality of pearl millet as fodder and primary source for cattle feed.

Arbuscular mycorrhizal fungi (AMF) favored the accumulation of secondary metabolites in leaves of lettuces in previous studies. When fertilized with selenium (Se), mycorrhizal lettuces had more proteins, sugars and minerals than non-mycorrhizal ones. However, Se contents were lower in mycorrhizal plants suggesting a negative correlation between Se and AMF applications. The aim of the present study was to test if Se fertilization interfered with AMF technology for enhancing secondary metabolites in lettuces. Green and red-leaf lettuces were or not inoculated with AMF and received or not different selenocompounds. Flavonols and anthocyanins were non-destructively measured. At harvest, growth, water status, chlorophylls, carotenoids, phenolics and antioxidant capacity were determined. In green-leaf lettuces Se application counteracted benefits of AMF on chlorophylls and carotenoids and decreased phenolics. In red-leaf lettuces, sodium selenite positively interacted with AMF in enhancing flavonols, but imidoselenocarbamate reduced flavonols in mycorrhizal plants. No significant interaction between AMF and Se was detected for the total antioxidant capacity in leaves of both types of lettuces. The efficiency of mycorrhizal technology for improving antioxidant compounds in the edible tissues of lettuces can be modified under Se fertilization, being the interaction positive or negative depending on lettuce cultivar, antioxidant compound and chemical form of selenocompound.

Alfalfa is a widely distributed forage legume whose leaves are high in protein content and whose stems are suitable for bioethanol production. However, alfalfa forage digestibility, quality and yield may vary under future climate change scenarios. This legume can establish double symbiosis with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi (AMF). The presence of AMF can modify the evolution of biomass production and partitioning during the vegetative growth of alfalfa. We hypothesised that mycorrhizal symbiosis may change the quantity and/or quality of carbohydrates and lignin in leaves and/or stems of alfalfa, with these changes being dependent on the atmospheric CO2 concentration at which plants are grown. Results showed that mycorrhizal alfalfa plants exposed to elevated CO2 had improved leaf, stem and root biomass, enhanced amount of hemicellulose and decreased concentration of lignin in cell walls of leaves as well as increased levels of glucose and fructose in stems compared with non-mycorrhizal alfalfa. These results indicated improved forage quality (leaves) and enhanced potential for bioethanol conversion (stems) in mycorrhizal alfalfa cultivated under elevated CO2. Moreover, the potential of stems for producing CH4 reinforced their suitability for the conversion of biomass into bioethanol.

Onion (Allium cepa L.) is a crop with great economic importance over the world. The vigor of seedlings plays a crucial role in the posterior growth and quality of bulbs. Application of humic substances (HS), inoculation of arbuscular mycorrhizal fungi (AMF) in the soil and enhancement of atmospheric CO2 are three factors that can influence plant growth and development. Therefore, our main objective was to assess the effect of each of the abovementioned factors, separately or interacting, on the metabolism and growth of onion seedlings before bulb formation and under greenhouse conditions. Results showed that these three factors appear as valid horticultural techniques for improving growth and quality of onion seedlings cultivated in greenhouse even when mycorrhizal colonization of roots does not achieve high rates. Beneficial effects of HS were additive to those of mycorrhizal inoculation or elevated CO2 (ECO2) on shoot and root biomass production. The triple interaction between exogenous HS application, mycorrhizal inoculation and ECO2 induced the highest accumulation of soluble sugars, proteins and proline in leaves, suggesting that such interaction was the most effective for increasing the quality of onion shoots as source organs for posterior growth and quality of bulbs and also for enhancing the tolerance of onion seedlings to environmental stresses.

Continued emissions of CO2, derived from human activities, increase atmospheric CO2 concentration. The CO2 rise stimulates plant growth and affects yield quality. Effects of elevated CO2 on legume quality depend on interactions with N2-fixing bacteria and mycorrhizal fungi. Growth at elevated CO2 increases photosynthesis under short-term exposures in C3 species. Under long-term exposures, however, plants generally acclimate to elevated CO2 decreasing their photosynthetic capacity. An updated survey of the literature indicates that a key factor, perhaps the most important, that characteristically influences this phenomenon, its occurrence and extent, is the plant source-sink balance. In legumes, the ability of exchanging C for N at nodule level with the N2-fixing symbionts creates an extra C sink that avoids the occurrence of photosynthetic acclimation. Arbuscular mycorrhizal fungi colonizing roots may also result in increased C sink, preventing photosynthetic acclimation. Defoliation (Anthyllis vulneraria, simulated grazing) or shoot cutting (alfalfa, usual management as forage) largely increases root/shoot ratio. During re-growth at elevated CO2, new shoots growth and nodule respiration function as strong C sinks that counteracts photosynthetic acclimation. In the presence of some limiting factor, the legumes response to elevated CO2 is weakened showing photosynthetic acclimation. This survey has identified limiting factors that include an insufficient N supply from bacterial strains, nutrient-poor soils, low P supply, excess temperature affecting photosynthesis and/or nodule activity, a genetically determined low nodulation capacity, an inability of species or varieties to increase growth (and therefore C sink) at elevated CO2 and a plant phenological state or season when plant growth is stopped.

Medicago sativa L. (alfalfa) can exhibit photosynthetic down-regulation when grown in greenhouse conditions under elevated atmospheric CO2. This forage legume can establish a double symbiosis with nitrogen fixing bacteria and arbuscular mycorrhizal fungi (AMF), which may increase the carbon sink effect of roots. Our aim was to assess whether the association of alfalfa with AMF can avoid, diminish or delay the photosynthetic acclimation observed in previous studies performed with nodulated plants. The results, however, showed that mycorrhizal (M) alfalfa at the end of their vegetative period had lower carbon (C) discrimination than non-mycorrhizal (NM) controls, indicating photosynthetic acclimation under ECO2 in plants associated with AMF. Decreased C discrimination was due to the acclimation of conductance, since the amount of Rubisco and the expression of genes codifying both large and small subunits of Rubisco were similar or slightly higher in M than in NM plants. Moreover, M alfalfa accumulated a greater amount of soluble sugars in leaves than NM plants, thus favoring a down-regulation effect on photosynthetic rates. The enhanced contents of sugars in leaves coincided with a reduced percentage of arbuscules in roots, suggesting decreased sink of carbohydrates from shoots to roots in M plants. The shorter life cycle of alfalfa associated with AMF in comparison with the NM controls may also be related to the accelerated photosynthetic acclimation in M plants. Further research is needed to clarify to what extent this behavior could be extrapolated to alfalfa cultivated in the field and subjected to periodic cutting of shoots under climatic change scenarios.

Human activities are increasing atmospheric CO2 concentration and temperature. Related to this global warming, periods of low water availability are also expected to increase. Thus, CO2 concentration, temperature and water availability are three of the main factors related to climate change that potentially may influence crops and ecosystems. In this report, we describe the use of growth chamber - greenhouses (GCG) and temperature gradient greenhouses (TGG) to simulate climate change scenarios and to investigate possible plant responses. In the GCG, CO2 concentration, temperature and water availability are set to act simultaneously, enabling comparison of a current situation with a future one. Other characteristics of the GCG are a relative large space of work, fine control of the relative humidity, plant fertirrigation and the possibility of light supplementation, within the photosynthetic active radiation (PAR) region and/or with ultraviolet-B (UV-B) light. In the TGG, the three above-mentioned factors can act independently or in interaction, enabling more mechanistic studies aimed to elucidate the limiting factor(s) responsible for a given plant response. Examples of experiments, including some aimed to study photosynthetic acclimation, a phenomenon that leads to decreased photosynthetic capacity under long-term exposures to elevated CO2, using GCG and TGG are reported.

Mycorrhizal inoculation can enhance the nutritional value of lettuces. However, the role of arbuscular mycorrhizal fungi (AMF) in biofortification of selenium (Se) in lettuce is unknown. We tested the capacity of two cultivars of lettuces, inoculated or not with AMF, for accumulating Se in shoots after applying sodium selenite or new synthesized organic selenocompounds. Sodium selenite was the most effective for increasing Se in shoots, but it decreased levels of macronutrients, micronutrients and proteins in one cultivar. Mycorrhizal inoculation reduced the accumulation of Se in leaves, but inoculated plants had higher contents of minerals, proteins and/or sugars than the non-inoculated controls supplied with Se. Mycorrhizal inoculation may impair the biofortification of lettuces with Se, but could be adequate for cultivating lettuces on soils rich in Se. The organic imidoselenocarbamate improved the effectiveness of AMF for enhancing growth, and proteins and sugars in leaves of one greenhouse-grown cultivar of lettuce.

Arbuscular mycorrhizal (AM) symbiosis can improve date palm growth and alleviate drought-related impacts than non-mycorrhizal plants due to the ability of AMF for modifying plant metabolism and physiology. Date palm (Phoenix dactylifera L.) is an important agricultural and commercial crop in the North of Africa and Middle Eastern countries. During the last decade, date palm plantations were subjected to degradation due to an extensive exploitation and to drastic environmental conditions such as drought. Currently, there is a growing interest in the valorization of water due to environmental problems and economic aspects. The use of arbuscular mycorrhizal fungi (AMF) can offer a possibility to overcome these problems. The objective of this study was to study the influence of different Glomus species-Glomus intraradices, G. mosseae and Complex Aoufous (native AMF)-on the development of date palm grown under two water regimes (optimal irrigation, 75 % of field capacity or water deficit, 25 % of field capacity). Our results revealed that the beneficial effect of mycorrhizal symbiosis on plant growth depended on the fungal species and the water regime applied to the palm date seedling. While the native Complex Aoufous was the most effective in increasing the shoot height and biomass under well-watered conditions, G. intraradices was the most beneficial fungus for improving growth of plants that undergo restricted water supply. This positive effect of G. intraradices under drought conditions was not related to an enhancement of the antioxidant enzymatic activities in leaves; the association of palm date with G. intradices caused an increase in the elasticity of cell walls in leaves and allowed maintaining high water content in leaves without lowering leaf water potential under stressful conditions. The adequate selection of the AMF species is crucial for improving growth of palm date seedlings, and it must be in accordance with the water regime that will be applied to plants.

Previous studies demonstrated that arbuscular mycorrhizal fungi (AMF) can induce the accumulation of carotenoids, phenolics, anthocyanins and some mineral nutrients in leaves of lettuce (Lactuca sativa L.) thus enhancing its nutritional quality. Our objectives were to know which carotenoids were the most accumulated in leaves of mycorrhizal lettuces and to assess the effect of AMF on tocopherols' levels in leaves of lettuce plants. AMF always enhanced growth and, in most cases, increased the levels of all major carotenoids, chlorophylls and tocopherols in green and red leaf lettuces. Since these molecules are also important nutraceuticals, mycorrhization emerges as reliable technique to enhance the nutritional value of edible vegetables. These results are compared with other methods developed to improve nutritional quality.

Lettuce (Lactuca sativa L.) is extensively grown and is the most widely used food crop for the called ¿Fourth Range¿ of vegetables. Lettuce exhibits healthy properties mainly due to the presence of antioxidant compounds (vitamins C and E, carotenoids, polyphenols) alongside significant fibre content and useful amounts of certain minerals. Lettuce can establish a mutualistic association with arbuscular mycorrhizal fungi (AMF). The establishment of the symbiosis involves a continuous cellular and molecular dialogue between both symbionts, which includes the activation of antioxidant, phenylpropanoid or carotenoid metabolic pathways. The presence of AMF colonizing roots of greenhouse-grown lettuces can induce an accumulation of secondary metabolites, vitamins and minerals in leaves that overcome the dilution effect due to the increased size of mycorrhizal plants. Therefore, AMF would allow the intake of minerals and compounds with antioxidant properties to be enhanced without increasing the consumption of lettuce in the diet. In addition, increased quantities of secondary metabolites may help lettuce plants to withstand biotic and abiotic stresses. Our review discusses the influence exerted by several environmental factors and agronomic practices on the ability of AMF for enhancing the levels of vitamins, nutraceuticals and minerals in leaves of green and red-leaf types of lettuces.

Lettuce (Lactuca sativa L.) is a major food crop within the European Union. The objective of this study was to test the potential nutritional quality of three types of lettuce consumed as salads: Lactuca sativa L. var. longifolia (commonly named Cogollos de Tudela) and two cultivars of Lactuca sativa L. var. capitata (Batavia Rubia Munguía and Maravilla de Verano). Distribution of sugars, proteins, minerals and antioxidant compounds (carotenoids, chlorophylls, phenolics, anthocyanins and ascorbate) between outer and inner leaves was tested. The potential benefits of each variety or cultivar were due to different compounds accumulated in leaves. Cogollos de Tudela showed higher levels of Mg and Ca in both external and internal leaves, and greater concentrations of Mn, chlorophylls and carotenoids in inner leaves than lettuces belonging to the var. capitata. Batavia Rubia Munguía had low quantity of Na and an important amount of K, Mg, Ca, Fe and Zn in outer leaves and it was the cultivar that accumulated the highest quantity of water in both outer and inner leaves. Maravilla de Verano showed the greatest contents of anthocyanins and ascorbate in external leaves. In the three cultivars some of the potentially beneficial compounds appeared in higher levels in the outer than in the inner leaves. Therefore, the complete elimination of the external leaves should be reconsidered when lettuces are consumed as salads or used as food crop for the `Fourth Range¿ of vegetables.

The association of Lactuca sativa L with arbuscular mycorrhizal fungi (AMF) can benefit growth and induce the accumulation of mineral nutrients and antioxidants in leaves. Our objectives were (1) to assess to what extent growing season influence growth and nutritional quality of the green-leaf Batavia Rubia Munguia (BRM) and the red-leaf Maravilla de Verano (MV) lettuce cultivars; (2) to test if the growing season affected the effectiveness of AMF as enhancers of the nutritional quality of the aforementioned cultivars; and (3) to check if inoculation with AMF allows extending the season to cultivate these two lettuce cultivars, without a loss of plant growth or nutritional quality. Results showed that winter Was the most favourable growing season for both types of lettuce but mycorrhizal plants cultivated in other seasons different from winter achieved higher or similar shoot biomass than their respective non-inoculated controls in winter. AMF induced the accumulation of Fe, proteins, carotenoids and anthocyanins in both cultivars of lettuce in winter and spring. In summer and autumn, both types of lettuce showed increased levels of anthocyanins when associated with AMF. Mycorrhizal BRM also had enhanced levels of K, sugars and ascorbate in winter and spring as well as increased amounts of Mg and Cu in winter and summer. Mycorrhizal MV had increased quantities of Cu, Zn and sugars in spring and Mn in autumn. After estimating intakes of mineral elements through the consumption

Many beech forests in Navarra, North of Spain, were deeply disturbed as a consequence of clear-cutting practices that involved the complete removal of a stand in a single harvest by heavy machinery. The regeneration of most clear-cut areas was left to occur naturally from the seed bank and from seeds provided by the surrounding beech trees. This review is integrating the results obtained from the study of tree physiology, soil biology and mycorrhizal communities in three nearby beech stands: one clear-cut in 2001; another clear-cut in 1996 and an unmanaged forest for at least the last century. The main objectives were (i) to study the microclimatic conditions inside the beech stands subjected to clear-cutting, then naturally regenerating from disturbance, and exhibiting very different tree size and density; (ii) to deepen the knowledge of some anatomical, physiological and biochemical parameters of beech trees that had successfully established within clear-cut areas with strong differences in microclimatic conditions and (iii) to know the biological properties of soils belonging to beech stands naturally regenerating from clear-cutting. We hypothesized that the soil biology in regenerating clear-cut beech stands of different ages could be markedly influenced by the microclimatic conditions determined by both tree size and density within each site, with the latter factor uncertain when stands are naturally regenerating from disturbance.

Arbuscular mycorrhizal fungi (AMF) can improve growth and nutritional quality of greenhouse-grown lettuces cultivated at ambient CO2. Moreover, mycorrhizal symbiosis is predicted to be important in defining plant responses to elevated atmospheric CO2 concentrations. Our main objective was to assess the effects of elevated CO2 on growth and nutritional quality of greenhouse-grown lettuces inoculated or not with AMF. Results showed that the accumulation of mineral nutrients (e.g. P, Cu, Fe) and antioxidant compounds (carotenoids, phenolics, anthocyanins, ascorbate) induced by AMF in leaves of lettuces cultivated at ambient CO2 may diminish or disappear under elevated CO2. It is hypothesized that a relevant quantity of photoassimilates could be used for improving shoot growth and spreading mycorrhizal colonization in detriment to the secondary metabolism. However, important differences can be found among different cultivars of lettuces.

The influence of mycorrhizal symbiosis, atmospheric CO2 concentration and the interaction between both factors on biomass production and partitioning were assessed in nodulated alfalfa (Medicago sativa L.) associated or not with arbuscular mycorrhizal fungi (AMF) and grown in greenhouse at either ambient (392 mu mol mol(-1)) or elevated (700 mu mol mol(-1)) CO2 air concentrations. Measurements were performed at three stages of the vegetative period of plants. Shoot and root biomass achieved by plants at the end of their vegetative period were highly correlated to the photosynthetic rates reached at earlier stages, and there was a significant relationship between CO2 exchange rates and total nodule biomass per plant. In non-mycorrhizal alfalfa, the production of leaves, stems and nodules biomass significantly increased when plants had been exposed to elevated CO2 concentration in the atmosphere for 4 weeks. Regardless CO2 concentration at which alfalfa were cultivated, mycorrhizal symbiosis improved photosynthetic rates and growth of alfalfa at early stages of the vegetative period and then photosynthesis decreased, which suggests that AMF shortened the vegetative period of the host plants. At final stages of the vegetative period, AMF enhanced both area and biomass of leaves as well as the leaves to stems ratio when alfalfa plants were cultivated at ambient CO2. The interaction of AMF with elevated CO2 improved root biomass and slightly increased the leaves to stems ratio at

Lettuce, a major food crop within the European Union and the most used for the so-called 'Fourth Range' of vegetables, can associate with arbuscular mycorrhizal fungi (AMF). Mycorrhizal symbiosis can stimulate the synthesis of secondary metabolites, which may increase plant tolerance to stresses and enhance the accumulation of antioxidant compounds potentially beneficial to human health. Our objectives were to assess (1) if the application of a commercial formulation of AMF benefited growth of lettuce under different types and degrees of water deficits; (2) if water restrictions affected the nutritional quality of lettuce; and (3) if AMF improved the quality of lettuce when plants grew under reduced irrigation. Two cultivars of lettuce consumed as salads, Batavia Rubia Munguia and Maravilla de Verano, were used in the study. Four different water regimes were applied to both non-mycorrhizal and mycorrhizal plants: optimal irrigation (field capacity [FC]), a water regime equivalent to 2/3 of FC, a water regime equivalent to 1/2 of FC and a cyclic drought (CD). Results showed that mycorrhizal symbiosis improved the accumulation of antioxidant compounds, mainly carotenoids and anthocyanins, and to a lesser extent chlorophylls and phenolics, in leaves of lettuce. These enhancements were higher under water deficit than under optimal irrigation. Moreover, shoot biomass in mycorrhizal lettuces subjected to 2/3 of FC were similar to those of non-mycorrhizal plants cultivated under well-watered conditions. In addition, lettuces subjected to 2/3 FC had similar leaf RWC than their respective well-watered controls, regardless of mycorrhizal inoculation. Therefore, results suggest that mycorrhizal symbiosis can improve quality of lettuce and may allow restrict irrigation without reducing production.

The improvement of the nutritional quality of lettuce by its association with arbuscular mycorrhizal fungi (AMF) has been recently reported in a previous study. The aim of this research was to evaluate if the fertilization with three P sources differing in water solubility affects the effectiveness of AMF for improving lettuce growth and nutritional quality. The application of either water-soluble P sources (Hewitt's solution and single superphosphate) or the water-insoluble (WI) fraction of a ¿rhizosphere-controlled fertilizer¿ did not exert negative effects on the establishment of the mycorrhizal symbiosis. AMF improved lettuce growth and nutritional quality. Nevertheless, the effect was dependent on the source of P and cultivar. Batavia Rubia Munguía (green cultivar) benefited more than Maravilla de Verano (red cultivar) in terms of mineral nutrients, total soluble sugars, and ascorbate contents. The association of lettuce with AMF resulted in greater quantities of anthocyanins in plants fertilized with WI, carotenoids when plants received either Hewitt's solution or WI, and phenolics regardless of the P fertilizer applied.

The use of chemical products has been a usual practice to reduce the incidence of soil-borne plant pathogens in both field and greenhouses. However, the application of chemicals causes soil and water contamination and severely reduces the diversity of the microflora in the treated soil. Therefore, finding alternative methods for controlling soil-borne plant pathogens has become essential for Agriculture and Horticulture in the future. Some of these alternatives are the use of tolerant cultivars, the employment of adequate management strategies and the development of biological methods. Among the possible appropriate cultural activities adequate irrigation, soil solarization, biofumigation, crop rotation and application of soil amendments should be taken into account. Biological methods would include the use - alone or combined - of antagonistic bacteria, fungal root endophytes, arbuscular mycorrhizal fungi (AMF), yeasts, viruses and soil fauna. The efficacy, possible problems and limitations of the application of biological agents to control soil-borne pathogens in different crop and ornamental plants are discussed in this review.