Asymbiotic mass production of the arbuscular mycorrhizal fungus Rhizophagus clarus

Arbuscular mycorrhizal (AM) symbiosis is a mutually beneficial interaction between fungi and land plants and promotes global phosphate cycling in terrestrial ecosystems. AM fungi are recognised as obligate symbionts that require root colonisation to complete a life cycle involving the production of propagules, asexual spores. Recently, it has been shown that Rhizophagus irregularis can produce infection-competent secondary spores asymbiotically by adding a fatty acid, palmitoleic acid. Furthermore, asymbiotic growth can be supported using myristate as a carbon and energy source for their asymbiotic growth to increase fungal biomass. However, the spore production and the ability of these spores to colonise host roots were still limited compared to the co-culture of the fungus with plant roots. Here we show that a combination of two plant hormones, strigolactone and jasmonate, induces the production of a large number of infection-competent spores in asymbiotic cultures of Rhizophagus clarus HR1 in the presence of myristate and organic nitrogen. Inoculation of asymbiotically-generated spores promoted the growth of host plants, as observed for spores produced by symbiotic culture system. Our findings provide a foundation for the elucidation of hormonal control of the fungal life cycle and the development of inoculum production schemes.

The Arbuscular Mycorrhizal Fungus Rhizophagus Clarus Improve Physiological Tolerance to Drought Stress in Soybean Plants

Soybean (Glycine max L.) is an economically important crop worldwide. However, increasingly long periods of drought have reduced the productivity of this crop. Studies have shown that inoculation with arbuscular mycorrhizal fungi (AMF) provides a potential alternative strategy for mitigating drought. In the present study, we measured the physiological and morphological performance of two soybean cultivars under drought in symbiosis with Rhizophagus clarus. Soybean plants Anta82 and Desafio, were grown in pots previously inoculated with R. clarus. Water deficit (WD) was imposed at the V3 development stage and maintained for 7 days. A control group was performed in parallel with well-irrigated plants in the absence of R. clarus in a greenhouse. Three and seven days after the WD imposition the analysis were performed. Cultivar Anta82 showed a higher percentage of colonization, N and K leaf content, whereas Desafio, showed higher water potential, water-use efficiency under WD, and thermal dissipation that allowed higher values for Fv/Fm, A, and PH under WD+AMF. The Principal Components Analysis results were able to demonstrate that both cultivars in water deficit with AMF colonization clustered together with well-watered plants. These findings suggest that AMF had an effect on plants in order to reduce drought physiological impairment.

Estabelecimento de Anadenanthera colubrina var. cebil sob inoculação micorrízica e fertilização no Pantanal brasileiro

Este trabalho objetivou avaliar o estabelecimento de Anadenanthera colubrina (Vell.) Brenan var. cebil [Griseb.] Altschul sob inoculação micorrízica e fertilização no Pantanal da Nhecolândia, MS. O experimento foi implantado em março de 2015 em ambiente de cordilheira parcialmente desmatada, em blocos ao acaso distribuídos no micro relevo, e parcelas subdivididas. Os principais tratamentos foram constituídos por mudas submetidas ou não (controle) à inoculação mista com Rhizophagus clarus e Gigaspora margarita, e aos tratamentos secundários de adubação com doses de sulfato de amônio e cloreto de potássio. Entre 2015 e 2017 foram avaliados a abertura do dossel das árvores remanescentes, o percentual de sobrevivência e o crescimento de A. colubrina. Melhores condições de sobrevivência foram verificadas na porção da cordilheira mais próxima à baía, sob sombreamento moderado e com a aplicação, no plantio, de 15 g de sulfato de amônio e de 5 g de cloreto de potássio por muda. A inoculação micorrízica promoveu incremento de 16% em diâmetro do colo aos 23 meses de idade, não aumentando a sobrevivência da espécie. Estudos complementares são necessários para subsidiar estratégias de manejo de A. colubrina, em condições de plantio no Pantanal da Nhecolândia.

Mycorrhizal fungi and phosphate fertilization in the production of Euterpe edulis seedlings

The present study evaluated the effect of arbuscular mycorrhizal fungi (AMF) inoculation on growth and nutrition of Euterpe edulis seedlings, supplemented or not with phosphate fertilization. The experiment was conducted in a greenhouse. The randomized block design, consisted of a 3x2 factorial arrangement and 4 replicates, with two phosphorus doses (0 and 50 mg dm-3 of soil), two microbiological treatments (Rhizophagus clarus; laroideoglomus etunicatum; R. clarus + C. etunicatum) and control (without fungus). Sowing and inoculation occurred concurrently in 2 kg plastic bags. Height, collar diameter, leaf area, dry shoot mass, macronutrient content and mycorrhizal colonization percentage were determined after 226 days. Regarding mycorrhizal colonization percentage, R. clarus resulted significantly beneficial for the production of E. edulis seedlings. In the absence of phosphate fertilization, R. clarus and mixed inoculum increased all biometric variables and macronutrient contents in seedlings. Therefore, it is concluded that AMF inoculations provide beneficial effects for growth and nutrition of E. edulis seedlings, resulting in more vigorous plants at a low-cost strategy. Highlights: Rhizophagus clarus resulted significantly beneficial for the production of E. edulis seedlings and in the absence of phosphate fertilization, and mixed inoculum ( clarus + Claroideoglomus etunicatum) increased all biometric variables and macronutrient contents in seedlings. The AMF inoculations provide beneficial effects for growth and nutrition of E. edulis seedlings, resulting in more vigorous plants at a low-cost strategy. The AMF, a biological agent of mutualistic associations with plants, constitutes an innovative approach to sustainable agriculture, contributing to increase plant survival rate, a key-factor for the successful reintroduction and conservation of E. edulis, as well as for its commercial exploitation.

Development of mycorrhizal soybean grown in copper-contaminated soil

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.

O CRESCIMENTO DA RUTA GRAVEOLENS L. É AFETADO PELA INOCULAÇÃO MICORRÍZICA

Introdução: A espécie Ruta graveolens L. é uma planta de origem francesa, pertencente à família das Rutaceas, conhecida popularmente como arruda, pode apresentar diversas atividades, entres elas: analgésica, anti-hemorrágica, anti-inflamatória, calmante, estimulante, repelente, vermicida, entre outras. Fungos micorrízicos arbusculares (FMAs) são micro-organismos que fazem simbiose com raízes das plantas. Sendo a arruda largamente utilizada como recurso medicinal, vem sendo utilizadas técnicas como a introdução de populações de FMAs para um aumento de produtividade, onde a efetividade micorrízica é geralmente estudada em termos de crescimento e absorção de nutrientes, em relação à planta não micorrizada, com variações de acordo com a espécie hospedeira e o FMA utilizado. Objetivo: O objetivo deste estudo foi estudar o crescimento e a absorção de fósforo (P) da Ruta graveolens L. inoculada com os FMAs Claroideoglomus etunicatum e/ou Rhizophagus clarus sob baixa (20 mg dm-3 de solo) e ou alta (200 mg dm-3 de solo) adição de P no solo. Material e métodos: As plantas foram crescidas em vasos com 3,5 kg de solo fumigado com um delineamento experimental inteiramente casualizado em fatorial 2 x 3: 2 níveis de P e 3 FMAs (2 FMAs inoculados ou não), no total 6 tratamentos, com seis repetições conduzidos em casa de vegetação por 4 meses. Foram determinados a massa seca das plantas, o conteúdo de P na parte aérea. Resultados: A produção de massa da planta foi aumentada significantemente com a inoculação dos FMAs. A maior produção de massa foi encontrada com a inoculação com o FMA C. etunicatum, aumentando em quase 3 vezes mais a produção de biomassa em relação ao controle não inoculado. Não observou-se diferenças significativas no conteúdo de P na parte aérea com a inoculação dos FMAs, porém, a adição de P ao solo aumentou significantemente o conteúdo de P na planta. Conclusão: A inoculação dos FMAs, estimulou o crescimento da arruda e que a inoculação com FMA C. etunicatum foi mais eficiente. A adição de P ao solo aumentou o conteúdo de P na planta.

PRODUCTION OF SEEDLINGS OF COLUBRINA GLANDULOSA PERKINS WITH DRILLING WASTE FROM OIL WELLS AND MYCORRHIZAL INOCULATION

Oil exploration, whether onshore or offshore, results in residues from the drilling of wells, called gravel. The use of this environmental liability in the production of seedlings for forest restoration could contribute to an appropriate destination for this waste. In the present study, the objective was to evaluate the effect of the substrate formulated with gravel, with and without inoculation with arbuscular mycorrhizal fungi (AMF), on the growth and nutritional status of seedlings of Colubrina glandulosa. The design used was completely randomized in a 5x2 factorial scheme, with five gravel doses (0, 5, 10, 15, and 20%), with and without inoculation with a mixture of AMF spores (Gigaspora margarita¸ Rhizophagus clarus, and Dentiscutata heterogama) with six repetitions, totaling 60 experimental units. Height (H) and stem diameter (SD) were evaluated at 30, 60, 90, and 120 days after seedling transplantation, when the plants were sectioned in shoots (branches + leaves) and roots, to determine dry biomass of shoots (DMS) and of roots (DMR), leaf area index (LAI), rate of length of fine roots colonized by AMF (COL), and chemical composition. The substrate obtained with the application of the lowest gravel dose (5%), without the mycorrhizal inoculation, provided significant increments in H, SD, LAI, DMS, DMR, and COL of the seedlings of Colubrina glandulosa, when compared to the other gravel doses and the presence of mycorrhizal inoculation, 120 days after seedling transplantation.

Farklı Mikoriza Türleri, Kompost ve Fosfat Kayacı Uygulamalarının Sorgum Bitkisinin Gelişimine Etkileri

The aim of this study was to determine the effects of different compost and rock phosphate doses applications with different mycorrhizal species inoculation on sorghum plant growth and nutrient uptake. Dosages 0, 20, 40 gr compost kg-1 soil as were used as compost, and 0, 2, 4 gr rock phosphate/soil as rock phosphate sources. Funnelformis mosseae, F. caledonius, Claroideoglomus etunicatum, Rhizophagus clarus, indigenous and cocktail (mixture) mycorrhizae were used. Shoot and root dry matter, P and Zn concentration and root percentages of mycorrhizal infection were determined. According to the research findings, mycorrhiza inoculation significantly increased the shoot and root dry matter, P, Zn and root infection of sorghum plant more than rock phosphate and compost applications. F. caledonius was determined as the most effective species. While 20 and 40 g compost kg-1 soil doses applications were most effective, it was concluded that the shortage of cultivation time resulted that the rock phosphate may not be sufficiently dissolved for nutrient supply to plant growth.