Adaptative Strategies in Gymnocalycium Species (Cactaceae) and the Presence of Ectomycorrhizae Associated with Survival in Arid Environments.

The Cactaceae family makes use of different strategies, both physiological and biochemical, for anatomical adjustments that allow them to grow and reproduce in arid environments. Morphological studies of Gymnocalycium have been scarce, and the anatomy and phytochemistry are still largely unknown. The aim of the present work was to analyze the structural, physiological, and biochemical features of Gymnocalycium marianae and G. oenanthemum, two endemic species of arid regions in Argentina. The anatomic structure, biomass, and photosynthetic pigments, as well as phenolic compound contents, were analyzed in the stem, spine, and root of both species. G. marianae showed stems with deeper substomatal chambers and a more developed photosynthetic tissue than G. oenanthemum. The spines of G. oenanthemum showed higher biomass, thicker epidermal and subepidermal cell walls, and a higher content of phenolic compounds than those of G. marianae. Ectomycorrhizae were observed for the first time in roots in both species. Roots of G. marianae showed high colonization, biomass, and content of phenolic compounds. Both species showed abundant mucilaginous fibers in the stem and root. Finally, these results show the strategies associated with the survival in xeric environments of two cacti species at risk of extinction. They could be useful for the development of ex situ conservation programs.

Plant Growth Promoting Bacteria and Arbuscular Mycorrhizae Improve the Growth of Persea americana var. Zutano under Salt Stress Conditions.

In Peru, almost 50% of the national agricultural products come from the coast, highlighting the production of avocado. Much of this area has saline soils. Beneficial microorganisms can favorably contribute to mitigating the effect of salinity on crops. Two trials were carried out with var. Zutano to evaluate the role of native rhizobacteria and two Glomeromycota fungi, one from a fallow (GFI) and the other from a saline soil (GWI), in mitigating salinity in avocado: (i) the effect of plant growth promoting rhizobacteria, and (ii) the effect of inoculation with mycorrhizal fungi on salt stress tolerance. Rhizobacteria P. plecoglissicida, and B. subtilis contributed to decrease the accumulation of chlorine, potassium and sodium in roots, compared to the uninoculated control, while contributing to the accumulation of potassium in the leaves. Mycorrhizae increased the accumulation of sodium, potassium, and chlorine ions in the leaves at a low saline level. GWI decreased the accumulation of sodium in the leaves compared to the control (1.5 g NaCl without mycorrhizae) and was more efficient than GFI in increasing the accumulation of potassium in leaves and reducing chlorine root accumulation. The beneficial microorganisms tested are promising in the mitigation of salt stress in avocado.

In vitro propagation of a cuban Arbuscular Mycorrhizal Fungal strain and factible bacteria's association / Propagación in vitro de una cepa cubana de Hongos Micorrízicos Arbusculares y su factible asociación a bacterias

ABSTRACT In vitro root cultivation techniques based on modified root systems are often used in studies on Arbuscular Mycorrhizal Fungi (AMF). It is a simplified but powerful tool to investigate AMF root colonization and development of the extraradical mycelium. The aim of this study was to establish and characterize the in vitro culture of a Cuban strain of Rhizophagus irregularis (INCAM 11) by using transformed chicory roots. For that, superficially disinfected propagules of R. irregularis were co-culture with the hairy transformed chicory roots on Modified Strullu and Romand (MSR) medium during five months. Spore germination was observed 3-5 days after surface disinfection. The first contact between AMF hyphae and roots occurred 1 - 3 days after germination and a significant production of extensive extraradical mycelium was observed. New spore formation started within 21 - 25 days. After 5 months, 2000 spores could be observed per plate which were able to germinate, colonize, establish and reproduce again spores when associated to young transformed roots of chicory. The most frequent associated microorganism to the in vitro culture of INCAM 11 was isolated and identified as Paenibacillus sp.

RESUMEN Las técnicas de cultivo de raíces in vitro basadas en sistemas de raíces modificadas se utilizan a menudo en los estudios sobre hongos micorrízicos arbusculares (HMA). Es una herramienta simplificada pero poderosa para investigar la colonización de las raíces de los HMA y el desarrollo del micelio extrarradical. El objetivo de este estudio fue establecer y caracterizar el cultivo in vitro de una cepa cubana de Rhizophagus irregularis (INCAM 11) utilizando raíces transformadas de achicoria. Para ello, propágulos de R. irregularis desinfectados superficialmente fueron co-cultivados con las raíces transformadas de achicoria en medio Strullu y Romand modificado (SRM) durante cinco meses. La germinación de las esporas se observó 3-5 días después de la desinfección superficial. El primer contacto entre las hifas y las raíces se produjo entre 1 y 3 días después de la germinación y se observó una producción significativa de micelio extrarradical. La formación de nuevas esporas comenzó entre 21 - 25 días. Después de 5 meses, se pudieron observar 2000 esporas por placa que fueron capaces de germinar, colonizar, establecer y reproducir nuevas esporas cuando se asociaron a raíces jóvenes transformadas de achicoria. El microorganismo asociado frecuentemente al cultivo in vitro de INCAM 11 fue aislado e identificado como Paenibacillus sp.

Respuesta del banano clon Valery en alta densidad a la inoculación con micorrizas y fósforo en Apartadó - Colombia

El cultivo de banano en el Urabá Antioqueño viene presentando disminución en los rendimientos, lo que exige la búsqueda de alternativas para incrementar o mantener la producción actual, entre las cuales, se encuentra el aumento en la proporción de fertilizantes inorgánicos, conllevando a sobrecostos y problemas ambientales. En vista de esta situación, se ha generado un interés por el uso de biofertilizantes, como el caso de las micorrizas (HFM), con las que se han demostrado beneficios al sistema suelo-planta. El objetivo de esta investigación fue evaluar el efecto de los HFM con la disminución de la dosis fosforada en el clon de banano Valery, en un sistema de alta densidad, bajo condiciones edafoclimáticas de Apartadó-Antioquia. Para ello, en los tratamientos, al momento de la siembra, se realizaron inoculaciones de 100 g de HFM comercial con 5 dosis de fósforo, que correspondieron a: 0, 25, 50, 75 y 100 kg*ha-1. Se midieron variables morfológicas, rendimiento y simbiosis micorrízica. El diseño experimental fue completamente al azar, con 3 repeticiones; cada unidad experimental estuvo constituida por 10 plantas contenidas en 5 sitios. La información se procesó con el programa estadístico SAS 9.1, se obtuvo el análisis de varianza y una prueba de comparación de medias (Tukey), con un nivel de significancia del 95 %. No se encontraron diferencias significativas en las variables morfológicas, pero sí en las variables productivas, siendo el tratamiento HFM + 50 kg P2O5*ha-1 el de mejor resultado y, además, presentó el mayor porcentaje de colonización micorrízica, con 59,5 %.

The banana crop in Uraba Antioqueño has been presenting a decrease in the yields, which requires the search for alternatives to increase or maintain current production, among which is the increase in the proportion of inorganic fertilizers leading to cost overruns and environmental problems. In view of this situation, there has been a growing interest in the use of biofertilizers such as mycorrhiza (HFM) with which multiple benefits to the soil-plant system have been demonstrated. The objective of this research was to evaluate the effect of HFM with the reduction of phosphorus dose in the Valery banana clone under a high-density system under edaphoclimatic conditions of Apartado-Antioquia. For this purpose, 100 g of commercial HFM were inoculated with 5 doses of phosphorus at time of sowing, corresponding to: 0, 25, 50, 75 and 100 kg*ha-1. Morphological variables, performance and mycorrhizal symbiosis were measured. The experimental design was completely random with 3 repetitions, each experimental unit was made up of 10 plants contained in 5 sites. The information was processed with the statistical program SAS 9.1, variance analysis was obtained and a mean comparison test (Tukey) with a significance level of 95 %. No significant differences were found in the morphological variables, but in the productive variables, the HFM + 50 Kg P2O5*ha-1 treatment was the best and also presented the highest percentage of mycorrhizal colonization with 59.5 %.

Influence of microbial consortia on the incidence of grey mold (Botrytis cinerea) in strawberry (Monterey variety)

Botrytis cinerea, the causal agent of grey mold disease, is one of the most destructive pathogens of strawberry crops, both in vegetative development and postharvest. The control of this pathogen is complex due to its aggressiveness and ability to attack and infect various plant tissues and is mainly based on chemical control; however, the incorrect use of pesticides, mainly due to overdosing, causes the presence of traces of these agrochemicals in the fruits, as well as the selection of pathogen resistance to fungicides, making it a risk to human health and the environment. The objective of the study was to use biological regulation strategies, with the application of microbial consortia made up of mycorrhizal fungi, antagonistic bacteria and Trichoderma harzianum, as an alternative for the management of grey mold in strawberry crops (Monterey variety) under field conditions. Treatments T4 (mycorrhizal fungi), T8 (mycorrhizal fungi, antagonistic bacteria and T. harzianum) and T2 (T. harzianum) presented the lowest incidence of the pathogen with 2.6, 3.1 and 3.6 %, respectively, compared to control plants with 16.6%. The influence of all biological treatments on the regulation of B. cinerea was greater than the control.

Botrytis cinerea, el agente causal de la enfermedad del moho gris, es uno de los patógenos más destructivos del cultivo de fresa, tanto en el desarrollo vegetativo como en poscosecha. El control de este patógeno es complejo, debido a su agresividad y capacidad de atacar e infectar diversos tejidos de la planta y se basa, principalmente, en el control químico; sin embargo, el uso incorrecto de plaguicidas, principalmente por sobredosificación, provoca la presencia de trazas de estos agroquímicos en los frutos, así como la selección de resistencia del patógeno a los fungicidas, convirtiéndolo en un riesgo para la salud humana y el ambiente. El objetivo del estudio fue utilizar estrategias de regulación biológica, con la aplicación de consorcios microbianos, conformados por hongos micorrícicos, bacterias antagonistas y Trichoderma harzianum, como alternativa para el manejo del moho gris, en cultivos de fresa (variedad Monterey), en condiciones de campo. Los tratamientos T4 (hongos micorrízicos), T8 (hongos micorrízicos, bacterias antagonistas y T. harzianum) y T2 (T. harzianum) presentaron la menor incidencia del patógeno, con 2,6, 3,1 y 3,6 %, respectivamente, en comparación con las plantas control, con 16,6 %. La influencia de todos los tratamientos biológicos en la regulación de B. cinerea fue mayor respecto al control.

Comprehensive Analysis of Phaseolus vulgaris SnRK Gene Family and Their Expression during Rhizobial and Mycorrhizal Symbiosis.

Sucrose non-fermentation-related protein kinase 1 (SnRK1) a Ser/Thr protein kinase, is known to play a crucial role in plants during biotic and abiotic stress responses by activating protein phosphorylation pathways. SnRK1 and some members of the plant-specific SnRK2 and SnRK3 sub-families have been studied in different plant species. However, a comprehensive study of the SnRK gene family in Phaseolus vulgaris is not available. Symbiotic associations of P. vulgaris with Rhizobium and/or mycorrhizae are crucial for the growth and productivity of the crop. In the present study, we identified PvSnRK genes and analysed their expression in response to the presence of the symbiont. A total of 42 PvSnRK genes were identified in P. vulgaris and annotated by comparing their sequence homology to Arabidopsis SnRK genes. Phylogenetic analysis classified the three sub-families into individual clades, and PvSnRK3 was subdivided into two groups. Chromosome localization analysis showed an uneven distribution of PvSnRK genes on 10 of the 11 chromosomes. Gene structural analysis revealed great variation in intron number in the PvSnRK3 sub-family, and motif composition is specific and highly conserved in each sub-family of PvSnRKs. Analysis of cis-acting elements suggested that PvSnRK genes respond to hormones, symbiosis and other abiotic stresses. Furthermore, expression data from databases and transcriptomic analyses revealed differential expression patterns for PvSnRK genes under symbiotic conditions. Finally, an in situ gene interaction network of the PvSnRK gene family with symbiosis-related genes showed direct and indirect interactions. Taken together, the present study contributes fundamental information for a better understanding of the role of the PvSnRK gene family not only in symbiosis but also in other biotic and abiotic interactions in P. vulgaris.

Management of Rhizosphere Microbiota and Plant Production under Drought Stress: A Comprehensive Review.

Drought generates a complex scenario worldwide in which agriculture should urgently be reframed from an integrative point of view. It includes the search for new water resources and the use of tolerant crops and genotypes, improved irrigation systems, and other less explored alternatives that are very important, such as biotechnological tools that may increase the water use efficiency. Currently, a large body of evidence highlights the role of specific strains in the main microbial rhizosphere groups (arbuscular mycorrhizal fungi, yeasts, and bacteria) on increasing the drought tolerance of their host plants through diverse plant growth-promoting (PGP) characteristics. With this background, it is possible to suggest that the joint use of distinct PGP microbes could produce positive interactions or additive beneficial effects on their host plants if their co-inoculation does not generate antagonistic responses. To date, such effects have only been partially analyzed by using single omics tools, such as genomics, metabolomics, or proteomics. However, there is a gap of information in the use of multi-omics approaches to detect interactions between PGP and host plants. This approach must be the next scale-jump in the study of the interaction of soil-plant-microorganism. In this review, we analyzed the constraints posed by drought in the framework of an increasing global demand for plant production, integrating the important role played by the rhizosphere biota as a PGP agent. Using multi-omics approaches to understand in depth the processes that occur in plants in the presence of microorganisms can allow us to modulate their combined use and drive it to increase crop yields, improving production processes to attend the growing global demand for food.

Diversity of Root-Associated Fungi of the Terrestrial Orchids Gavilea lutea and Chloraea collicensis in a Temperate Forest Soil of South-Central Chile.

The diversity of orchid mycorrhizal fungi (OMF) and other beneficial root-associated fungi in temperate forests has scarcely been examined. This study aimed to analyze the diversity of mycorrhizal and rhizosphere-associated fungal communities in the terrestrial orchids Gavilea lutea and Chloraea collicensis growing in high-orchid-population-density areas in the piedmont of the Andes Cordillera with native forest (Nothofagus-Araucaria) and Coastal Cordillera with an exotic plantation (Pinus-Eucalyptus) in south-central Chile. We focused on rhizosphere-inhabiting and peloton-associated OMF in a native forest (Andes Cordillera) and a mixed forest (Coastal Cordillera). The native terrestrial orchids G. lutea and C. collicensis were localized, mycorrhizal root segments were taken to isolate peloton-associated OMF, and rhizosphere soil was taken to perform the metabarcoding approach. The results revealed that Basidiomycota and Ascomycota were the main rhizosphere-inhabiting fungal phyla, showing significant differences in the composition of fungal communities in both sites. Sebacina was the most-abundant OMF genera in the rhizosphere of G. lutea growing in the native forest soil. In contrast, Thanatephorus was the most abundant mycorrhizal taxa growing in the rhizosphere of orchids from the Coastal Cordillera. Besides, other OMF genera such as Inocybe, Tomentella, and Mycena were detected. The diversity of OMF in pelotons differed, being mainly related to Ceratobasidium sp. and Tulasnella sp. These results provide evidence of differences in OMF from pelotons and the rhizosphere soil in G. lutea growing in the Andes Cordillera and a selection of microbial communities in the rhizosphere of C. collicensis in the Coastal Cordillera. This raises questions about the efficiency of propagation strategies based only on mycorrhizal fungi obtained by culture-dependent methods, especially in orchids that depend on non-culturable taxa for seed germination and plantlet development.

Asymmetric Interaction Between Two Mycorrhizal Fungal Guilds and Consequences for the Establishment of Their Host Plants.

Arbuscular mycorrhiza (AM) and ectomycorrhiza (EcM) are the most abundant and widespread types of mycorrhizal symbiosis, but there is little and sometimes conflicting information regarding the interaction between AM fungi (AMF) and EcM fungi (EcMF) in soils. Their competition for resources can be particularly relevant in successional ecosystems, which usually present a transition from AM-forming herbaceous vegetation to EcM-forming woody species. The aims of this study were to describe the interaction between mycorrhizal fungal communities associated with AM and EcM hosts naturally coexisting during primary succession on spoil banks and to evaluate how this interaction affects growth and mycorrhizal colonization of seedlings of both species. We conducted a greenhouse microcosm experiment with Betula pendula and Hieracium caespitosum as EcM and AM hosts, respectively. They were cultivated in three-compartment rhizoboxes. Two lateral compartments contained different combinations of both host plants as sources of fungal mycelia colonizing the middle compartment, where fungal biomass, diversity, and community composition as well as the growth of each host plant species' seedlings were analyzed. The study's main finding was an asymmetric outcome of the interaction between the two plant species: while H. caespitosum and associated AMF reduced the abundance of EcMF in soil, modified the composition of EcMF communities, and also tended to decrease growth and mycorrhizal colonization of B. pendula seedlings, the EcM host did not have such effects on AM plants and associated AMF. In the context of primary succession, these findings suggest that ruderal AM hosts could hinder the development of EcM tree seedlings, thus slowing the transition from AM-dominated to EcM-dominated vegetation in early successional stages.

The effect of arbuscular mycorrhizal fungi on the phenolic compounds profile, antioxidant activity and grain yields in wheat cultivars growing under hydric stress.

BACKGROUND: Hydric stress affects the production of wheat (Triticum aestivum L.) worldwide, making some tools necessary to cope with the decrease in rainfall. A sustainable alternative is the use of arbuscular mycorrhizal fungi (AMF) as biofertilisers. Here, we analysed the effects of AMF strains adapted or non-adapted to hyper-arid conditions on the phenolic profiles and antioxidant activities of wheat grains from two cultivars with contrasting tolerance to osmotic stress (Ilustre, moderately tolerant; and Maxi, tolerant) grown with and without hydric stress. RESULTS: Eight phenolic compounds were detected, apigenin-C-pentoside-C-hexoside I being the most abundant and showing an increase of 80.5% when inoculated with the fungus Funneliformis mosseae (FM) obtained from Atacama Desert under normal irrigation with respect to non-mycorrhizal (NM) plants. NM treatments were associated with higher grain yields. FM showed a noticeable effect on most phenolic compounds, with an increase up to 30.2% in apigenin-C-pentoside-C-hexoside III concentration under hydric stress with respect to normal irrigation, being also responsible for high antioxidant activities such as ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) activities. CONCLUSION: Inoculation with FM adapted to hydric stress produced improvements in phenolics composition and antioxidant activities in grains from wheat plants growing under hydric stress conditions, improving their food quality and supporting the development of further studies to determine whether the use of adapted AMF could be a realistic tool to improve grain quality in a scenario of increasing hydric stress conditions. © 2021 Society of Chemical Industry.

Arbuscular mycorrhizal fungi in wheat grown in copper contaminated soil / Fungos micorrízicos arbusculares no cultivo de trigo em solo contaminado com cobre

At high soil concentrations, copper (Cu) is toxic to plant development. Symbiosis carried out between microorganisms and plant species are alternatives to minimize plant toxicity in copper contaminated soil. The present study aimed to select species of arbuscular mycorrhizal fungi for the development of wheat plants in copper contaminated soil. The experimental design was completely randomized in a 4 × 6 factorial arrangement, with four sources of inocula: three species of arbuscular mycorrhizae (Acaulospora colombiana, Gigaspora Margarita and Rhizophagus clarus) and one without inoculum (control), and six doses of copper in the soil (0, 80, 160, 240, 320, and 400 mg kg-1), with seven replications. Plant height, root length, root volume, root dry mass, specific surface area, average root diameter, root, shoot and grain Cu content and mycorrhizal colonization rate were evaluated. Root dry mass and mycorrhizal colonization were negatively affected by high Cu doses in the soil. The mycorrhizal isolates Acaulospora Colombiana and Gigaspora Margarita provide greater wheat height, root length and specific surface area and lower Cu content. Mycorrhizal colonization with the fungi Acaulospora Colombiana, Gigaspora Margarita and Rhizophagus clarus results in lower copper content in wheat shoots and grains.(AU)

Em elevadas concentrações no solo, o cobre (Cu) é tóxico para o desenvolvimento dos vegetais. Simbioses realizadas entre microrganismos e espécies vegetais são alternativas para minimizar a toxidez das plantas em solo contaminado com cobre. O trabalho teve como objetivo selecionar espécies de fungos micorrízicos arbusculares para o desenvolvimento de plantas de trigo em solo contaminado com cobre. O delineamento experimental foi inteiramente casualizado em arranjo fatorial 4 × 6, sendo quatro fontes de inóculos: três espécies de micorrizas arbusculares (Acaulospora colombiana, Gigaspora margarita e Rhizophagus clarus) e sem inóculo (testemunha) e seis doses de cobre no solo (0, 80, 160, 240, 320 e 400 mg kg-1), com sete repetições. Avaliou-se a altura de plantas, comprimento de raiz, volume de raízes, massa seca de raiz, área superficial específica, diâmetro médio de raiz, teor de cobre na raiz, na parte aérea e no grão e porcentagem de colonização micorrízica. A massa seca de raiz e a colonização micorrízica foram afetadas negativamente com altas doses de Cu no solo. Os isolados micorrízicos Acaulospora Colombiana e Gigaspora Margarita proporcionam maior altura, comprimento de raiz e área superficial específica e menor teor de Cu no grão na cultura do trigo. A colonização micorrízica com os fungos Acaulospora Colombiana, Gigaspora Margarita e Rhizophagus clarus resulta em menor teor de cobre na parte aérea e nos grãos do trigo.(AU)

Development of mycorrhizal soybean grown in coppercontaminated soil / Desenvolvimento da soja micorrízada cultivada em solo contaminado com cobre

High concentrations of copper in the soil are toxic to the development of plants and microorganisms. The aim of this study was to select arbuscular mycorrhizal fungi efficient for the development and yield of soybeangrown in copper-contaminated soil. The experiment was laid out in a completely randomized design with a 7 × 4 factorial arrangement corresponding to seven rates of copper (0, 80, 160, 240, 320, 400, and 480 mg kg-1 of soil) and four inocula (uninoculated control and three mycorrhizal fungi, namely, Acaulospora colombiana, Dentiscutata heterogama and Rhizophagus clarus), in seven replicates. Shoot height; collar diameter; number of grains per plant; shoot and root-system dry mass; leaf area; specific root surface; copper content and accumulation in the shoots, roots, and grain; chlorophyll parameters; and mycorrhizal colonization percentage were evaluated. Inoculation with the arbuscular mycorrhizal fungi Acaulospora colombiana, Dentiscutata heterogama and Rhizophagus clarus increases the phenological and physiological parameters of soybean and its yield when grown in soil contaminated with up to 480 mg kg-1 of copper applied to the soil. The Rhizophagus clarus isolate provides greater development and yield in soybean grown in soil contaminated with up to 480 mg kg-1 of copper applied to the soil, as compared with the other isolates.(AU)

O cobre em elevada concentração no solo torna-se tóxico ao desenvolvimento das plantas e microrganismo. O trabalho objetivou selecionar fungos micorrízicos arbusculares eficientes para o desenvolvimento e produtividade da soja cultivada em solo contaminado com cobre. O delineamento experimental foi em Inteiramente casualizado em arranjo fatorial 7 × 4, sendo, sete doses de cobre (0, 80, 160, 240, 320, 400 e 480 mg de cobre kg-1 de solo), quatro inóculos (testemunha sem inoculação e três fungos micorrízicos: Acaulospora colombiana, Dentiscutata heterogama e Rhizophagus clarus), com 7 repetições. Avaliou-se a altura da parte aérea, diâmetro do colo, número de grão por planta, massa seca da parte aérea e sistema radicular, área foliar, área superficial específica de raízes, teores e acúmulo de cobre na parte aérea, radicular e no grão, parâmetros da clorofila, e porcentagem de colonização micorrízica. A inoculação com fungos micorrízicos arbusculares Acaulospora colombiana, Dentiscutata heterogama, Rhizophagus clarus aumenta os parâmetros fenológicos e fisiológicos da soja e a sua produtividade soja em solo contaminado com até 480 mg kg-1 de cobre aplicado no solo. O isolado Rhizophagus clarus promove maior desenvolvimento da soja e aumenta sua produtividade em solo contaminado com até 480 mg kg-1 de cobre aplicado no solo em relação aos demais isolados.(AU)

Yield increase of corn inoculated with a commercial arbuscular mycorrhizal inoculant in Brazil / Rendimento de grãos da cultura do milho com inoculante micorrízico arbuscular comercial no Brasil

Arbuscular mycorrhizal fungi (AMF) play an important role in plant growth. However, there are no reports of legally commercialized AMF-based inoculants for agricultural crops in Brazil. The objective of this research was to evaluate the agronomic efficiency of a Rhizophagus intraradices inoculant in combination with phosphate fertilization in grain yield of corn under different edaphoclimatic conditions in Brazil. Experiments were conducted in five Brazilian states (Goiás, Mato Grosso, Minas Gerais, Rio Grande do Sul and Santa Catarina) in a 2 x 3 factorial scheme, with two inoculation treatments (inoculated and non-inoculated seeds) and three doses of phosphate fertilization (0, 50 and 100% of the recommended P). At the end of the crop cycle (stages R4-R5), inoculation provided increases in biomass (average of 48%) regardless of the applied dose of P, higher P absorption, and 54% average increase in grain yield. In conclusion, the mycorrhizal inoculant increases biomass yield, P uptake and corn grain yield under different edaphoclimatic conditions in Brazil, especially in soils that originally had low or medium levels of available P.(AU)

Os fungos micorrízicos arbusculares (FMA) desempenham um papel importante no crescimento das plantas, no entanto, não há relatos de inoculantes legais baseados em AMF para culturas agrícolas no Brasil. O objetivo deste trabalho foi avaliar a eficiência agronômica de um inoculante a base de Rhizophagus intraradices em combinação com a adubação fosfatada no rendimento de grãos de milho sob diferentes condições edafoclimáticas no Brasil. Os experimentos foram conduzidos em cinco estados brasileiros (Goiás, Mato Grosso, Minas Gerais, Rio Grande do Sul e Santa Catarina) em esquema fatorial 2 x 3, com dois tratamentos de inoculação (sementes inoculadas e não inoculadas) e três doses de adubação fosfatada (0, 50 e 100% do P recomendado). No final do ciclo da cultura (estágios R4-R5), a inoculação proporcionou aumentos na biomassa (média de 48%), independentemente da dose aplicada de P, maior absorção de P e aumento médio de 54% no rendimento de grãos. Conclui-se que o inoculante micorrízico arbuscular aumenta a produção de biomassa, a absorção de P e a produtividade de grãos de milho em diferentes condições edafoclimáticas no Brasil, especialmente em solos que originalmente apresentavam níveis baixos ou médios de P.(AU)

Zinc toxicity in seedlings of three trees from the Fabaceae associated with arbuscular mycorrhizal fungi.

Due to diverse human activities zinc (Zn) may reach phytotoxic levels in the soil. Here, we evaluated the differential sensibility of three Brazilian tree species from the Fabaceae to increasing soil Zn concentrations and its physiological response to cope with excess Zn. A greenhouse experiment was conducted with the species: Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, and the addition of 0, 200, 400 and 600 mg Zn kg-1 to the soil. Plants were harvested after three months of cultivation, and growth, root symbiosis, biochemical markers and elemental composition were analyzed. Soil Zn addition reduced seedling growth, irrespective of the species, with a strong reduction in M. caesalpiniaefolia. Regarding root symbiosis, in N2-fixing species, nitrogenase activity was reduced by the highest Zn concentrations. Zn addition caused plants nutritional imbalances, mainly in roots. The content of photosynthetic pigments in leaves decreased up to 40%, suggesting that high Zn contents interfered with its biosynthesis, and altered the content of foliar polyamines and free amino acids, depending on the species and the soil Zn concentration. Zn toxicity in M. caesalpiniaefolia plants was observed at available soil Zn concentrations greater than 100 mg kg-1 (DTPA-extractable), being the most sensitive species and E. speciosa was moderately sensitive. S. parahyba was a moderately tolerant species, which seems to be related to polyamines accumulation and to mycorrhizal association. This last species has the potential for revegetation of areas with moderately high soil Zn concentration and for phytostabilization purposes. Future research evaluating the tolerance to multiple metal stress under field conditions should confirm S. parayba suitability in Zn contaminated areas of tropical regions.

Extended cognition in plants: is it possible?

Plants do not possess brains or neurons. However, they present astonishingly complex behaviors such as information acquisition, memory, learning, decision making, etc., which helps these sessile organisms deal with their ever-changing environments. As a consequence, they have been proposed to be cognitive and intelligent, an idea which is becoming increasingly accepted. However, how plant cognition could operate without a nervous central system remains poorly understood and new insights on this topic are urgently needed. According to the Extended Cognition hypothesis, cognition may also occur beyond the limits of the body, encompassing objects from the environment. This was shown possible in humans and spiders, who actively manipulate their external environment to extend their cognitive capacity. Here, we propose that extended cognition may also be found in plants and could partly explain the complexity of plant behavior. We suggest that plants can extend their cognitive abilities to the environment they manipulate through the root influence zone and the mycorrhizal fungi that associate with them. The possibility of a cognitive process involving organisms from different kingdoms is exciting and worthwhile exploring as it may provide key insights into the origin and evolution of cognition.

Septoglomus mexicanum, a new species of arbuscular mycorrhizal fungi from semiarid regions in Mexico.

Septoglomus mexicanum is here described as a new species of arbuscular mycorrhizal fungi (AMF; Glomeromycota) based on morphological and phylogenetic analyses. It was isolated from rhizospheric soil of two endemic Mexican legumes: Prosopis laevigata and Mimosa luisana, which grow in semiarid regions of central Mexico. Septoglomus mexicanum is characterized by forming globose spores of (154.5-)202.8(-228.9) µm diam and a spore wall consisting of four layers (SWL1-SWL4): outer wall layer (SWL1) hyaline, evanescent, (1.7-)3.2(-4.3) µm thick; SWL2 laminate and smooth, orange to reddish orange, (3.1-)4.5(-6.1) µm thick; SWL3 laminate, smooth, reddish orange to reddish brown, (4.1-)5.1(-5.7) µm thick; and SWL4 hyaline, semiflexible, (0.93-)1.2(-1.4) µm thick. None of the spore wall layers stain with Melzer's reagent. The subtending hypha has a color from yellowish to golden and presents a septum on spore base. Septoglomus mexicanum can be distinguished from all other Septoglomus species by spore size and color, by spore wall structure (four layers), and by color change of the subtending hypha. Phylogenetic analysis based on the AMF extended DNA barcode covering a 1.5-kb fragment of the small subunit (SSU), internal transcribed spacer region (ITS1-5.8S-ITS2), and the large subunit (LSU) of rRNA genes places S. mexicanum in the genus Septoglomus, separated from other described Septoglomus species, especially S. turnauae, with whom it could be confused morphologically. All available sequences in public databases suggest that this new fungal species has not yet been previously detected. Thus, there are currently 149 Glomeromycota species registered in Mexico, representing 47.4% of the known species worldwide.

Yield increase of corn inoculated with a commercial arbuscular mycorrhizal inoculant in Brazil / Rendimento de grãos da cultura do milho com inoculante micorrízico arbuscular comercial no Brasil

ABSTRACT: Arbuscular mycorrhizal fungi (AMF) play an important role in plant growth. However, there are no reports of legally commercialized AMF-based inoculants for agricultural crops in Brazil. The objective of this research was to evaluate the agronomic efficiency of a Rhizophagus intraradices inoculant in combination with phosphate fertilization in grain yield of corn under different edaphoclimatic conditions in Brazil. Experiments were conducted in five Brazilian states (Goiás, Mato Grosso, Minas Gerais, Rio Grande do Sul and Santa Catarina) in a 2 x 3 factorial scheme, with two inoculation treatments (inoculated and non-inoculated seeds) and three doses of phosphate fertilization (0, 50 and 100% of the recommended P). At the end of the crop cycle (stages R4-R5), inoculation provided increases in biomass (average of 48%) regardless of the applied dose of P, higher P absorption, and 54% average increase in grain yield. In conclusion, the mycorrhizal inoculant increases biomass yield, P uptake and corn grain yield under different edaphoclimatic conditions in Brazil, especially in soils that originally had low or medium levels of available P.

RESUMO: Os fungos micorrízicos arbusculares (FMA) desempenham um papel importante no crescimento das plantas, no entanto, não há relatos de inoculantes legais baseados em AMF para culturas agrícolas no Brasil. O objetivo deste trabalho foi avaliar a eficiência agronômica de um inoculante a base de Rhizophagus intraradices em combinação com a adubação fosfatada no rendimento de grãos de milho sob diferentes condições edafoclimáticas no Brasil. Os experimentos foram conduzidos em cinco estados brasileiros (Goiás, Mato Grosso, Minas Gerais, Rio Grande do Sul e Santa Catarina) em esquema fatorial 2 x 3, com dois tratamentos de inoculação (sementes inoculadas e não inoculadas) e três doses de adubação fosfatada (0, 50 e 100% do P recomendado). No final do ciclo da cultura (estágios R4-R5), a inoculação proporcionou aumentos na biomassa (média de 48%), independentemente da dose aplicada de P, maior absorção de P e aumento médio de 54% no rendimento de grãos. Conclui-se que o inoculante micorrízico arbuscular aumenta a produção de biomassa, a absorção de P e a produtividade de grãos de milho em diferentes condições edafoclimáticas no Brasil, especialmente em solos que originalmente apresentavam níveis baixos ou médios de P.

Phosphorus Acquisition Efficiency Related to Root Traits: Is Mycorrhizal Symbiosis a Key Factor to Wheat and Barley Cropping?

Wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) are major crops cultivated around the world, thus playing a crucial role on human diet. Remarkably, the growing human population requires a significant increase in agricultural production in order to feed everybody. In this context, phosphorus (P) management is a key factor as it is component of organic molecules such as nucleic acids, ATP and phospholipids, and it is the most abundant macronutrient in biomass after nitrogen (N), although being one of the scarcest elements in the lithosphere. In general, P fertilization has low efficiency, as only a fraction of the applied P is acquired by roots, leaving a substantial amount to be accumulated in soil as not readily available P. Breeding for P-efficient cultivars is a relatively low cost alternative and can be done through two mechanisms: i) improving P use efficiency (PUE), and/or ii) P acquisition efficiency (PAE). PUE is related to the internal allocation/mobilization of P, and is usually represented by the amount of P accumulated per biomass. PAE relies on roots ability to acquire P from the soil, and is commonly expressed as the relative difference of P acquired under low and high P availability conditions. In this review, plant adaptations related to improved PAE are described, with emphasis on arbuscular mycorrhizal (AM) symbiosis, which is generally accepted to enhance plant P acquisition. A state of the art (1980-2018) of AM growth responses and P uptake in wheat and barley is made to discuss about the commonly accepted growth promoting effect and P increased uptake by AM fungi and the contrasting evidence about the generally accepted lack of positive responses in both plant species. Finally, the mechanisms by which AM symbiosis can affect wheat and barley PAE are discussed, highlighting the importance of considering AM functional diversity on future studies and the necessity to improve PAE definition by considering the carbon trading between all the directly related PAE traits and its return to the host plant.

Changes in microbiological attributes of a Red Latosol under different cropping systems / Alterações dos atributos microbiológicos em um Latossolo Vermelho sob diferentes sistemas de manejo

The objective of this study was to evaluate changes in microbiological attributes of soils under different growing systems. Three cropping systems were evaluated (1) no-tillage system (NTS); (2) conventional tillage system (CTS); and (3) newly scarified no-tillage system (SNTS). The three systems were maintained for 20 years. In addition, a primary forest (PF) fragment was used as a reference. Soil samples were collected at depths of 0.0 - 0.1 m, 0.1 - 0.2 m, and 0.2 - 0.3 m. The following variables were measured: microbial biomass carbon (MBC); soil respirometry (RESP) using the fumigation and incubation method; microbial biomass nitrogen (MBN) using fumigation and extraction; metabolic quotient (qCO2) using the RESP/MBC ratio; and number of spores (NS) of mycorrhizal fungi by plate counting of spores extracted from the soil by wet sieving. Treatments were arranged in a completely randomized block design with five replicates. The different management systems affected the soil microbiota, especially in the superficial layer of 0.0 - 0.1 m. At a depth of 0.0 - 0.2 m, the PF presented significantly higher values for all analyzed attributes, except for NS. There were no significant differences in the studied characteristics between the NTS and SNTS at the three depths, indicating that scarification performed only once in the NTS was not sufficient to produce changes in soil microbiological attributes. However, the adoption of the CTS for 20 years promoted a decrease in MBC and MBN. RESP and NS were not significantly different between the cropping systems. Principal component analysis indicated a significant difference in microbiological characteristics between the PF and the areas under management. Therefore, different growing systems change the soil microbiota, and the lower the degree of tilling (NTS and SNTS), the smaller the changes in soil microbiological attributes.[...](AU)

O objetivo deste trabalho foi avaliar alterações nos atributos microbiológicos do solo em diferentes sistemas de manejo. Avaliou-se três tipos de manejo de solo (1) sistema de plantio direto -SPD; (2) plantio convencional - PC, ambos estabelecidos a 20 anos e (3) sistema de plantio direto de 20 anos recém escarificado - SPDE. Além desses, um fragmento de floresta primária (FP) foi usado como referência. Amostras de solo foram coletadas nas profundidades de 0,0 - 0,1; 0,1 - 0,2 e 0,2 - 0,3 m e determinados o carbono da biomassa microbiana (CBM) e a respirometria do solo (RESP) pelo método da fumigação e incubação, o nitrogênio da biomassa microbiana (NBM) determinado por fumigação e extração, o quociente metabólico (qCO2) pela razão entre RESP/CBM, e o número de esporos de fungos micorrízicos (nESP) por contagem em placa sob microscópio dos esporos extraídos do solo por peneiramento úmido. Os dados foram analisados como delineamento inteiramente ao acaso com cinco repetições. Os diferentes manejos influenciaram a microbiota do solo, destacadamente na camada superficial de solo 0,0 - 0,1 m. Na profundidade de 0,0 - 0,2 m a FP observou-se valores significativamente maiores para todos os atributos analisados, exceto nESP. O SPD e SPDE não diferiram nas profundidades para nenhum dos atributos, mostrando que a escarificação realizada apenas uma vez no SPD, não foi suficiente para produzir alterações sobre os atributos microbiológicos do solo. Entretanto, o manejo do solo em PC por 20 anos promoveu reduções no CBM e NBM. A RESP não se diferenciou entre os manejos, assim como o nESP. Na análise de componentes principais houve evidente distância, em termos de atributos microbiológicos, entre a FP e as áreas sob manejo. Conclui-se que os diferentes manejos de solo alteram a microbiota, sendo que, quanto menor a intensidade do manejo (SPD e SPDE) menores são as alterações nos atributos microbiológicos do solo.[...](AU)

Arbuscular mycorrhizal fungal communities in the rhizosphere of a continuous cropping soybean system at the seedling stage

Arbuscular mycorrhizae (AM) fungi play a crucial role in the growth of soybean; however, the planting system employed is thought to have an effect on AM fungal communities in the rhizosphere. This study was performed to explore the influence of continuous soybean cropping on the diversity of Arbuscular mycorrhizal (AM) fungi, and to identify the dominant AM fungus during the seedling stage. Three soybean cultivars were planted under two and three years continuous cropping, respectively. The diversity of AM fungi in the rhizosphere soil at the seedling stage was subsequently analyzed using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that an increase in cropping years improved the colonization rate of AM in all three soybean cultivars. Moreover, the dominant species were found to be Funneliformis mosseae and Glomus species. The results of cluster analysis further confirmed that the number of years of continuous cropping significantly affected the composition of rhizospheric AM fungal communities in different soybean cultivars.(AU)