Arbuscular Mycorrhizal Fungi Improve the Performance of Tempranillo and Cabernet Sauvignon Facing Water Deficit under Current and Future Climatic Conditions.

Climate change (CC) threatens Mediterranean viticulture. Rhizospheric microorganisms may be crucial for the adaptation of plants to CC. Our objective was to assess whether the association of two grapevine varieties with arbuscular mycorrhizal fungi (AMF) increases grapevine's resilience to environmental conditions that combine elevated atmospheric CO2, increased air temperatures, and water deficit. Tempranillo (T) and Cabernet Sauvignon (CS) plants, grafted onto R110 rootstocks, either inoculated (+M) or not (-M) with AMF, were grown in temperature-gradient greenhouses under two environmental conditions: (i) current conditions (ca. 400 ppm air CO2 concentration plus ambient air temperature, CATA) and (ii) climate change conditions predicted by the year 2100 (700 ppm of CO2 plus ambient air temperature +4 °C, CETE). From veraison to maturity, for plants of each variety, inoculation treatment and environmental conditions were also subjected to two levels of water availability: full irrigation (WW) or drought cycles (D). Therefore, the number of treatments applied to each grapevine variety was eight, resulting from the combination of two inoculation treatments (+M and -M), two environmental conditions (CATA and CETE), and two water availabilities (WW and D). In both grapevine varieties, early drought decreased leaf conductance and transpiration under both CATA and CETE conditions and more markedly in +M plants. Photosynthesis did not decrease very much, so the instantaneous water use efficiency (WUE) increased, especially in drought +M plants under CETE conditions. The increase in WUE coincided with a lower intercellular-to-atmospheric CO2 concentration ratio and reduced plant hydraulic conductance. In the long term, mycorrhization induced changes in the stomatal anatomy under water deficit and CETE conditions: density increased in T and decreased in CS, with smaller stomata in the latter. Although some responses were genotype-dependent, the interaction of the rootstock with AMF appeared to be a key factor in the acclimation of the grapevine to water deficit under both current and future CO2 and temperature conditions.

Prospecting the Resilience of Several Spanish Ancient Varieties of Red Grape under Climate Change Scenarios.

BACKGROUND: Climate change results in warmer air temperatures and an uncertain amount and distribution of annual precipitations, which will directly impact rainfed crops, such as the grapevine. Traditionally, ancient autochthones grapevine varieties have been substituted by modern ones with higher productivity. However, this homogenization of genotypes reduces the genetic diversity of vineyards which could make their ability to adapt to challenges imposed by future climate conditions difficult. Therefore, this work aimed to assess the response of four ancient grapevine varieties to high temperatures under different water availabilities, focusing on plant water relations, grape technological and phenolic maturity, and the antioxidant capacity of the must. METHODS: The study was conducted on fruit-bearing cuttings grown in pots in temperature-gradient greenhouses. A two-factorial design was established where two temperature regimes, ambient and elevated (ambient + 4 °C), were combined with two water regimes, full irrigation and post-veraison deficit irrigation, during fruit ripening. RESULTS: There were significant differences among the ancient varieties regarding plant water relations and fruit quality. CONCLUSION: This research underlines the importance of evaluating the behavior of ancient grapevine varieties that could offer good options for the adaptation of viticulture to future climate conditions.

Grape berry transpiration influences ripening and must composition in cv. Tempranillo (Vitis vinifera L.).

The implications of grape berry transpiration for the ripening process and final grape composition were studied. An experiment was conducted, under controlled conditions, with fruit-bearing cuttings of Vitis vinifera L. cv. Tempranillo. Three doses of the antitranspirant di-1-p-menthene were applied directly to the bunch at the onset of veraison: 1%, 5%, and 10% (v/v) (D1, D5, and D10, respectively). A treatment with bunches sprayed with water (D0) was also included as a control. Grape and bunch transpiration, and total soluble solids (TSS) accumulation rate decreased as the dose of antitranspirant increased, thus resulting in the lengthening of the ripening period. Bunch transpiration rates were linearly correlated with the elapsed time between veraison and maturity, and with the TSS accumulation rate. The evolution of pH, malic acid and total skin anthocyanins during ripening did not show remarkable changes as a consequence of the artificially reduced bunch transpiration. However, a decoupling between TSS and anthocyanins was observed. At maturity, the bunches treated with D10 had significantly lower must acidity and higher pH and extractable anthocyanin levels, these differences being likely associated with the lengthening of the ripening period. The results show a clear implication of grape transpiration for the ripening process and final grape composition, and give new hints on the direct application of antitranspirants to the bunch as a way to regulate sugar accumulation while avoiding the concurrent delay of color development.

Atmospheric CO2 concentration affects the life cycle, yield, and fruit quality of early maturing edible legume cultivars.

BACKGROUND: Elevated CO2 usually reduces levels of proteins and essential micronutrients in crops. The adoption of early maturing varieties may minimize the deleterious effect of climate change on farming activities. Legumes stand out for their high nutritional quality, so the objective was to study whether the atmospheric CO2 concentration affected the growth, yield, and food quality of early maturing cultivars of peas, snap beans, and faba beans. Plants grew in greenhouses either at ambient (ACO2 , 392 µmol mol-1 ) or under elevated (ECO2 , 700 µmol mol-1 ) CO2 levels. Minerals, proteins, sugars, and phenolic compounds were measured in grains of peas and faba beans, and in pods of snap beans. RESULTS: The effect of ECO2 depended on legume species, being more evident for food quality than for vegetative growth and yield. The ECO2 increased Fe and P in faba bean grains, and Ca in snap bean pods. Under ECO2 , grains of pea and faba bean increased levels of proteins and phenolics, respectively, and the sugars-to-protein ratio decreased in pods of snap beans. CONCLUSION: Early maturing varieties of legumes appear to be an interesting tool to cope with the negative effects that a long exposure to rising CO2 can exert on food quality. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mycorrhizal impact on competitive relationships and yield parameters in Phaseolus vulgaris L. - weed mixtures.

Arbuscular mycorrhizal fungi (AMF) are known to improve plant growth and nutrition and therefore are likely to affect the competitive relationships between crops and weeds. In this study, we evaluated whether AMF (Funneliformis mosseae, Rhizoglomus fasciculatum, Rhizoglomus intraradices) change plant competition between Phaseolus vulgaris and the weeds Solanum nigrum L., Digitaria sanguinalis L., and Ipomoea purpurea L. Mycorrhizal colonization, aggressivity index, photosynthetic rates, and yield parameters were measured. While the presence of AMF reduced the total biomass of D. sanguinalis and S. nigrum when grown in competition with P. vulgaris, it increased the total biomass of I. purpurea when grown with P. vulgaris. Significantly, elevated mycorrhizal growth responses (38-44%) improved the competitive ability of I. purpurea. In contrast, the competitive ability of S. nigrum was increased only when plants colonized by R. intraradices. The total protein content of P. vulgaris pods when in competition was negatively affected by AMF, thus leading to low nutritional quality. The results suggest that AMF have the potential to affect the outcome of weed-P. vulgaris competition. We demonstrate that not only colonization with AMF but also AMF species can affect the competitive relationships between crops and weeds, and thus, AMF represent key soil organisms to be taken into account in sustainable weed management strategies.

Assessment of Nutritional and Quality Properties of Leaves and Musts in Three Local Spanish Grapevine Varieties Undergoing Controlled Climate Change Scenarios.

The market demand together with the need for alternatives to withstand climate change led to the recovery of autochthonous grapevine varieties. Under climate change, the summer pruning of vineyards may lead to an increase of vegetative residuals of nutritional and medicinal interest. The objectives of our study were (1) to evaluate the nutritional properties of the leaves of three local Spanish grapevines (Tinto Velasco, TV, Pasera, PAS, and Ambrosina, AMB) when grown under climate change conditions, and (2) to test the potentiality of these grapevines as suitable candidates to be cultivated under climate change scenarios based on the quality of their must. Experimental assays were performed with fruit-bearing cuttings grown in temperature gradient greenhouses that simulate rising CO2 (700 µmol mol-1) and warming (ambient temperature +4 °C), either acting alone or in combination. TV and AMB were the most and the least affected by air temperature and CO2 concentration, respectively. The interaction of elevated CO2 with high temperature induced the accumulation of proteins and phenolic compounds in leaves of TV, thus enhancing their nutritional properties. In PAS, the negative effect of high temperature on protein contents was compensated for by elevated CO2. Warming was the most threatening scenario for maintaining the must quality in the three varieties, but elevated CO2 exerted a beneficial effect when acting alone and compensated for the negative effects of high temperatures. While TV may be a candidate to be cultivated in not very warm areas (higher altitudes or colder latitudes), PAS behaved as the most stable genotype under different environmental scenarios, making it the most versatile candidate for cultivation in areas affected by climate change.

Mycorrhizal Fungi as Bioprotectors of Crops Against Verticillium Wilt-A Hypothetical Scenario Under Changing Environmental Conditions.

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.

The Exploitation of Local Vitis vinifera L. Biodiversity as a Valuable Tool to Cope with Climate Change Maintaining Berry Quality.

(1) Background: The associated increase in global mean surface temperature together with raised atmospheric carbon dioxide (CO2) concentration is exerting a profound influence on grapevine development (phenology) and grape quality. The exploitation of the local genetic diversity based on the recovery of ancient varieties has been proposed as an interesting option to cope with climate change and maintaining grape quality. Therefore, this research aimed to characterize the potential fruit quality of genotypes from seven local old grapevine varieties grown under climate change conditions. (2) Methods: The study was carried out on fruit-bearing cuttings (one cluster per plant) that were grown in pots in temperature gradient greenhouses (TGG). Two treatments were applied from fruit set to maturity: (1) ambient CO2 (400 ppm) and temperature (T) (ACAT) and (2) elevated CO2 (700 ppm) and temperature (T + 4 °C) (ECET). (3) Results: Results showed that some of the old genotypes tested remained quite stable during the climate change conditions in terms of fruit quality (mainly, total soluble solids and phenolic content) and of must antioxidant properties. (4) Conclusion: This research underlines the usefulness of exploiting local grapevine diversity to cope with climate change successfully, although further studies under field conditions and with whole plants are needed before extrapolating the results to the vineyard.

Differential Flag Leaf and Ear Photosynthetic Performance Under Elevated (CO2) Conditions During Grain Filling Period in Durum Wheat.

Elevated concentrations of CO2 (CO2) in plants with C3 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 µmol 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.

Aminoacids and Flavonoids Profiling in Tempranillo Berries Can Be Modulated by the Arbuscular Mycorrhizal Fungi.

(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.

Mycorrhizal symbiosis affects ABA metabolism during berry ripening in Vitis vinifera L. cv. Tempranillo grown under climate change scenarios.

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.

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.

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.

Increased nutritional value in food crops.

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.

Increased photosynthetic acclimation in alfalfa associated with arbuscular mycorrhizal fungi (AMF) and cultivated in greenhouse under elevated CO2.

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.

Effectiveness of arbuscular mycorrhizal fungi (AMF) for inducing the accumulation of major carotenoids, chlorophylls and tocopherol in green and red leaf lettuces.

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.

Water deficit improved the capacity of arbuscular mycorrhizal fungi (AMF) for inducing the accumulation of antioxidant compounds in lettuce leaves.

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 Munguía 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.

Improvement of nutritional quality of greenhouse-grown lettuce by arbuscular mycorrhizal fungi is conditioned by the source of phosphorus nutrition.

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.

Arbuscular mycorrhizal fungi (AMF) improved growth and nutritional quality of greenhouse-grown lettuce.

Lettuce can be associated with arbuscular mycorrhizal fungi (AMF). This symbiosis involves a molecular dialogue between fungus and plant that includes the activation of antioxidant, phenylpropanoid, or carotenoid pathways. The objective of this study was to test if the association of lettuce with AMF benefited plant growth and increased the contents of compounds potentially beneficial for human health. Results showed that AMF improved growth of lettuce, thus producing a dilution effect on the concentrations of some mineral nutrients (e.g., Ca and Mn). However, Cu, Fe, anthocyanins, carotenoids, and, to a lesser extent, phenolics appeared in higher concentrations (on a wet basis) in mycorrhizal than in nonmycorrhizal plants.

To what extent are soil amendments useful to control Verticillium wilt?

The genus Verticillium includes several species that attack economically important crops throughout the world. The control of Verticillium spp. becomes especially difficult when they form microsclerotia that can survive in the field soil for several years. It has been common practice to fumigate soil with chemicals such as methyl bromide and/or chloropicrin to control soil-borne fungal pathogens. Other chemicals that are used against Verticillium spp. are the antifungal antibiotic aureofungin, the fungicides benomyl, captan, carbendazim, thiram, azoxystrobin and trifloxystrobin and the plant defence activator acibenzolar-S-methyl. However, the potential risks involved in applying phytochemicals to crop plants for both the environment and human health, together with their limited efficacy for controlling Verticillium-induced diseases, support the need to find alternatives to replace their use or improve their efficacy. Soil amendment with animal or plant organic debris is a cultural practice that has long been used to control Verticillium spp. However, today the organic farming industry is becoming a significant player in the global agricultural production scene. In this review, some of the main results concerning the efficacy of several soil amendments as plant protectors against Verticillium spp. are covered, and the limitations and future perspectives of such products are discussed in terms of the control of plant diseases.