Open Access
Overview of the use of biochar from main cereals to stimulate plant growth
(Carnegie Institution por Science, 2022) Martínez Gómez, Ángela; Poveda Arias, Jorge; Escobar, Carolina; Institute for Multidisciplinary Research in Applied Biology - IMAB
The total global food demand is expected to increase up to 50% between 2010 and 2050; hence, there is a clear need to increase plant productivity with little or no damage to the environment. In this respect, biochar is a carbon-rich material derived from the pyrolysis of organic matter at high temperatures with a limited oxygen supply, with different physicochemical characteristics that depend on the feedstock and pyrolysis conditions. When used as a soil amendment, it has shown many positive environmental effects such as carbon sequestration, reduction of greenhouse gas emissions, and soil improvement. Biochar application has also shown huge benefits when applied to agri-systems, among them, the improvement of plant growth either in optimal conditions or under abiotic or biotic stress. Several mechanisms, such as enhancing the soil microbial diversity and thus increasing soil nutrient-cycling functions, improving soil physicochemical properties, stimulating the microbial colonization, or increasing soil P, K, or N content, have been described to exert these positive effects on plant growth, either alone or in combination with other resources. In addition, it can also improve the plant antioxidant defenses, an evident advantage for plant growth under stress conditions. Although agricultural residues are generated from a wide variety of crops, cereals account for more than half of the world¿s harvested area. Yet, in this review, we will focus on biochar obtained from residues of the most common and relevant cereal crops in terms of global production (rice, wheat, maize, and barley) and in their use as recycled residues to stimulate plant growth. The harvesting and processing of these crops generate a vast number and variety of residues that could be locally recycled into valuable products such as biochar, reducing the waste management problem and accomplishing the circular economy premise. However, very scarce literature focused on the use of biochar from a crop to improve its own growth is available. Herein, we present an overview of the literature focused on this topic, compiling most of the studies and discussing the urgent need to deepen into the molecular mechanisms and pathways involved in the beneficial effects of biochar on plant productivity.
Open Access
The Pbo cluster from Pseudomonas syringae pv. phaseolicola NPS3121 is thermoregulated and required for phaseolotoxin biosynthesis
(MDPI, 2021) Guardado-Valdivia, Lizeth; Chacón-López, Alejandra; Murillo Martínez, Jesús; Poveda Arias, Jorge; Hernández Flores, José Luis; Xoca-Orozco, Luis; Aguilera, Selene; Institute for Multidisciplinary Research in Applied Biology - IMAB
The bean (Phaseolus vulgaris) pathogen Pseudomonas syringae pv. phaseolicola NPS3121 synthe-sizes phaseolotoxin in a thermoregulated way, with optimum production at 18 °C. Gene PSPPH_4550 was previously shown to be thermoregulated and required for phaseolotoxin bio-synthesis. Here, we established that PSPPH_4550 is part of a cluster of 16 genes, the Pbo cluster, included in a genomic island with a limited distribution in P. syringae and unrelated to the posses-sion of the phaseolotoxin biosynthesis cluster. We identified typical non-ribosomal peptide syn-thetase, and polyketide synthetase domains in several of the pbo deduced products. RT-PCR and the analysis of polar mutants showed that the Pbo cluster is organized in four transcriptional units, including one monocistronic and three polycistronic. Operons pboA and pboO are both es-sential for phaseolotoxin biosynthesis, while pboK and pboJ only influence the amount of toxin produced. The three polycistronic units were transcribed at high levels at 18 °C but not at 28 °C, whereas gene pboJ was constitutively expressed. Together, our data suggest that the Pbo cluster synthesizes secondary metabolite(s), which could participate in the regulation of phaseolotoxin biosynthesis.
Open Access
AtCube: performing pathogen-root infection tests on Arabidopsis thaliana in a completely controlled way
(Elsevier, 2022) Poveda Arias, Jorge; Institute for Multidisciplinary Research in Applied Biology - IMAB
Arabidopsis thaliana represents the main model plant for the experimental analysis of plant genetics and developmental biology of photoautotrophic organisms, due to characteristics such as size, life cycle, fecundity, genetics and its easy experimental manipulation. In turn, A. thaliana is used as a model plant in plant-microorganism interaction studies, being of great importance in the knowledge of the form of infection of numerous plant pathogens. The present work is based on the development of an A. thaliana plant growth system in Phytatray II boxes and culture substrate, trying to establish a system that is free of contamination, completely controlled, self-sufficient, reproducible and standardized, called AtCube. Through the use of different necrotrophic and biotrophic/hemibiotrophic root-pathogens, bacteria, fungi and oomycetes, and the comparison with a conventional system of growth in plots, various results are analyzed on the effects of pathogens on plants and the advantages and differences of the AtCube system. This work makes it possible to highlight that the AtCube system represents a methodology that allows obtaining results similar to other systems but with important advantages regarding its standardization, rigor and reproducibility with respect to studies with A. thaliana and root pathogens. Furthermore, it could represent an equally efficient system in studies with other plant species and the application of foliar pathogens and/or beneficial microorganisms.
Open Access
Endophytic fungi as direct plant growth promoters for sustainable agricultural production
(Springer, 2021) Poveda Arias, Jorge; Eugui Arrizabalaga, Daniel; Abril Urías, Patricia; Velasco, Pablo; Institute for Multidisciplinary Research in Applied Biology - IMAB
Current rates of population growth require the development of new agricultural strategies to feed the world human and livestock. The massive use of agricultural chemicals causes serious damage to the environment, and to human and animal health. For this reason, the use of endophytic fungi represents a biological alternative in increasing agricultural productivity in a sustainable way. This group of microorganisms, which inhabit plant tissues and organs without causing symptoms of damage, includes a great diversity of filamentous fungi and yeasts that are capable of increasing agricultural productivity. Some of the mechanisms involved in promoting plant growth by means of endophytic fungi include the increasing access to nutrients (nitrogen, phosphorus, potassium, zinc, iron, etc.), production of plant hormones, the ethylene amount reduction, or increase in water acquisition rate. This review tries to compile all the works carried out in the last decades on endophytic fungi use as plant growth promoters with great potential in agriculture.
Open Access
Activation of sweet pepper defense responses by novel and known biocontrol agents of the genus Bacillus against Botrytis cinerea and Verticillium dahliae
(Springer, 2022) Poveda Arias, Jorge; Calvo, Javier; Barquero, Marcia; González Andrés, Fernando; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The Fresno-Benavente Pepper (F-BP) Protected Geographical Indication (PGI) is a horticultural crop characterized by its great agronomic, economic and cultural importance in the region of Castilla y León (Spain). Field production is threatened by verticillium wilt caused by Verticillium dahliae and postharvest losses due to grey mould caused by Botrytis cinerea. Eight Bacillus spp. strains endophytically isolated from F-BP roots were used in the study. By conducting an in vitro antagonism study, we found that all Bacillus strains were effective against B. cinerea and five of them showed high antagonism against V. dahliae, with B. siamensis and B. proteolyticus strains being the most effective against both pathogens. Eight Bacillus strains were used for an infection test in F-BP fruits and plants to test their activity against both fungal pathogens. We report that Bacillus thuringiensis, B. siamensis and B. pumilus (SCFC 1–2) could control B. cinerea in pepper fruits through direct action and local activation of plant defences. In the case of V. dahliae root infection, plant roots inoculated with B. siamensis and B. proteolyticus were able to significantly decrease the occurrence of disease through direct action and local activation of jasmonic acid as a defence response. Therefore, we propose that B. siamensis could be used to control B. cinerea and V. dahliae in F-BP fruits and plants, respectively, through direct antagonism as well as the induction of local plant defence responses.
Open Access
Filamentous fungi as biocontrol agents in olive (Olea europaea L.) diseases: mycorrhizal and endophytic fungi
(Elsevier, 2021) Poveda Arias, Jorge; Baptista, Paula; Institute for Multidisciplinary Research in Applied Biology - IMAB
Olive (Olea europaea) is a crop of great agronomic, economic and cultural interest for the Mediterranean Basin, although the increase in world demand for olive oil is expanding its cultivation by other countries in the southern hemisphere. The main olive pathogens include bacteria (Pseudomonas savastanoi pv. savastanoi, Xylella fastidiosa), fungi (Colletotrichum spp., Verticillium dahliae, Fusarium spp. Rhizoctonia solani), oomycetes (Phytophthora spp.) and nematodes (Meloidogyne spp.). To combat these pathogens, different biocontrol strategies have been developed with bacteria and yeasts, although its capacity for establishment in the field entails several difficulties. In this sense, filamentous fungi represent an efficient and effective alternative in the control of the different pathogens of the olive tree. The present review compiles all the studies existing so far in the biocontrol of these pathogens through the use of mycorrhizal and endophytic filamentous fungi, making a separate section for the genus Trichoderma due to the special interest that their use has generated. The mechanisms used by these fungi include competition for space and nutrients, parasitism, antibiosis or activation of the plant's defensive responses, among others.
Open Access
Editorial: Beneficial effects of fungal endophytes in major agricultural crops
(Frontiers Media, 2022) Poveda Arias, Jorge; Baptista, Paula; Sacristán, Soledad; Velasco, Pablo; Institute for Multidisciplinary Research in Applied Biology - IMAB
Endophytic microorganisms are those that can dwell within plant tissues without any external sign of infection or other harmful effects on the host plants (Burragoni and Jeon, 2021). In recent decades, the important role that both bacterial and fungal endophytes play in plant growth and development, as well as in their ability to survive in their environment, has been identified (Burragoni and Jeon, 2021). Endophytic fungi can be found colonizing any plant organ, presenting a very different distribution and diversity among plants of different species, among plants of the same species, and even among organs of the same plant (Aamir et al., 2020). In crops, endophytic fungi act through different beneficial pathways, as biofertilizers promoting plant growth, as biological control agents of pathogens and pests or as inducers of tolerance under abiotic stresses, having great importance in the development of new strategies for sustainable agriculture (Aamir et al., 2020). These benefits for crops have been studied in the papers published in this Research Topic: promotion of plant growth in tomato (Paradza et al.), cotton (Silva et al.) and wheat (Asim et al.), increased tolerance under salt stress in tritordeum and perennial ryegrass (Toghueo et al.), as biological control agents against pathogenic fungi through antibiosis and mycoparasitism (Silva et al.), or as insecticidal agents through activation of systemic plant defenses (Paradza et al.; Agbessenou et al.), among others.
Open Access
Fungal endophytes of Brassicaceae: molecular interactions and crop benefits
(Carnegie Institution por Science, 2022) Poveda Arias, Jorge; Díaz González, Sandra; Díaz Urbano, María; Velasco, Pablo; Sacristán, Soledad; Institute for Multidisciplinary Research in Applied Biology - IMAB
Brassicaceae family includes an important group of plants of great scientific interest, e.g., the model plant Arabidopsis thaliana, and of economic interest, such as crops of the genus Brassica (Brassica oleracea, Brassica napus, Brassica rapa, etc.). This group of plants is characterized by the synthesis and accumulation in their tissues of secondary metabolites called glucosinolates (GSLs), sulfur-containing compounds mainly involved in plant defense against pathogens and pests. Brassicaceae plants are among the 30% of plant species that cannot establish optimal associations with mycorrhizal hosts (together with other plant families such as Proteaceae, Chenopodiaceae, and Caryophyllaceae), and GSLs could be involved in this evolutionary process of non-interaction. However, this group of plants can establish beneficial interactions with endophytic fungi, which requires a reduction of defensive responses by the host plant and/or an evasion, tolerance, or suppression of plant defenses by the fungus. Although much remains to be known about the mechanisms involved in the Brassicaceae-endophyte fungal interaction, several cases have been described, in which the fungi need to interfere with the GSL synthesis and hydrolysis in the host plant, or even directly degrade GSLs before they are hydrolyzed to antifungal isothiocyanates. Once the Brassicaceae-endophyte fungus symbiosis is formed, the host plant can obtain important benefits from an agricultural point of view, such as plant growth promotion and increase in yield and quality, increased tolerance to abiotic stresses, and direct and indirect control of plant pests and diseases. This review compiles the studies on the interaction between endophytic fungi and Brassicaceae plants, discussing the mechanisms involved in the success of the symbiosis, together with the benefits obtained by these plants. Due to their unique characteristics, the family Brassicaceae can be seen as a fruitful source of novel beneficial endophytes with applications to crops, as well as to generate new models of study that allow us to better understand the interactions of these amazing fungi with plants.
Open Access
Agronomic and metabolomic side-effects of a divergent selection for indol-3-ylmethylglucosinolate content in kale (Brassica oleracea var. acephala)
(MDPI, 2021) Poveda Arias, Jorge; Velasco, Pablo; Haro, Antonio de; Johansen, Tor J.; McAlvay, Alex C.; Möllers, Christian; Mølmann, Jorgen A.B.; Ordiales, Elena; Rodríguez, Víctor Manuel; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
Brassica oleracea var. acephala (kale) is a cruciferous vegetable widely cultivated for its leaves and flower buds in Europe and a food of global interest as a 'superfood'. Brassica crops accumulate phytochemicals called glucosinolates (GSLs) which play an important role in plant defense against biotic stresses. Studies carried out to date suggest that GSLs may have a role in the adaptation of plants to different environments, but direct evidence is lacking. We grew two kale populations divergently selected for high and low indol-3-ylmethylGSL (IM) content (H-IM and L-IM, respectively) in different environments and analyzed agronomic parameters, GSL profiles and metabolomic profile. We found a significant increase in fresh and dry foliar weight in H-IM kale populations compared to L-IM in addition to a greater accumulation of total GSLs, indole GSLs and, specifically, IM and 1-methoxyindol-3-ylmethylGSL (1MeOIM). Metabolomic analysis revealed a significant different concentration of 44 metabolites in H-IM kale populations compared to L-IM. According to tentative peak identification from MS interpretation, 80% were phenolics, including flavonoids (kaempferol, quercetin and anthocyanin derivates, including acyl flavonoids), chlorogenic acids (esters of hydroxycinnamic acids and quinic acid), hydroxycinnamic acids (ferulic acid and p-coumaric acid) and coumarins. H-IM kale populations could be more tolerant to diverse environmental conditions, possibly due to GSLs and the associated metabolites with predicted antioxidant potential.
Open Access
Mechanisms involved in drought stress tolerance triggered by rhizobia strains in wheat
(Frontiers Media, 2022) Barquero, Marcia; Poveda Arias, Jorge; Laureano Marín, Ana M.; Ortiz Liébana, Noemí; Brañas, Javier; González Andrés, Fernando; Institute for Multidisciplinary Research in Applied Biology - IMAB
Rhizobium spp. is a well-known microbial plant biostimulant in non-legume crops, but little is known about the mechanisms by which rhizobia enhance crop productivity under drought stress. This work analyzed the mechanisms involved in drought stress alleviation exerted by Rhizobium leguminosarum strains in wheat plants under water shortage conditions. Two (LBM1210 and LET4910) of the four R. leguminosarum strains significantly improved the growth parameters (fresh and dry aerial weight, FW and DW, respectively), chlorophyll content, and relative water content (RWC) compared to a non-inoculated control under water stress, providing values similar to or even higher for FW (+4%) and RWC (+2.3%) than the non-inoculated and non-stressed control. Some other biochemical parameters and gene expression explain the observed drought stress alleviation, namely the reduction of MDA, H2O2 (stronger when inoculating with LET4910), and ABA content (stronger when inoculating with LBM1210). In agreement with these results, inoculation with LET4910 downregulated DREB2 and CAT1 genes in plants under water deficiency and upregulated the CYP707A1 gene, while inoculation with LBM1210 strongly upregulated the CYP707A1 gene, which encodes an ABA catabolic enzyme. Conversely, from our results, ethylene metabolism did not seem to be involved in the alleviation of drought stress exerted by the two strains, as the expression of the CTR1 gene was very similar in all treatments and controls. The obtained results regarding the effect of the analyzed strains in alleviating drought stress are very relevant in the present situation of climate change, which negatively influences agricultural production.