Evaluation of water stress and co-inoculation of Azospirillum brasilense and Rhizobium tropici in beans (Phaseolus vulgaris l) / Avaliação do estratégio de água e co-inoculação de Azospirillum brasilense e Rhizobium tropici in beans (Phaseolus vulgaris l) / Evaluación del estrés hídrico y la coinoculación de Azospirillum brasilense y Rhizobium tropici en frijoles (Phaseolus vulgaris l)

Climate change has caused major changes in abiotic factors, with water stress as the greatest threat to agricultural production. The measures aimed at alleviating the problems caused by this limiting production factor have occurred through the adoption of sustainable strategies, especially microbial biotechnology, which uses the interactions between the microorganism and the plant, ensuring productive quality and inducing plant resistance to stresses biotic and abiotic. The objective of the present work was to evaluate the biological nitrogen fixation and the development of bean seedlings, with co-inoculation of two types of inoculants, which were subjected to water stress by different pot capacities. The experiment was conducted in a greenhouse, at Universidade Paranaense - UNIPAR, from April to June 2019. The experimental design was completely randomized (DIC), with 5 replications, 16 treatments and 80 experimental units. The cultivar used was SCS Riqueza. The parameters evaluated were pot capacity (25%, 50%, 75% and 90%); small, large and total nodules, shoot and root length, dry and fresh weight, total carbon and nitrogen. The evaluation of the morphological parameters of the bean seedlings indicated that the co- inoculation technique promoted beneficial effects for the dry mass parameters of shoot, nodule and root. The analysis of the percentage of carbon and nitrogen in the tissues of the seedlings provided an increase in the concentration of these elements in treatments that involved co-inoculation (Azospirillum brasilensis and Rhizobium tropici) with pot capacities of 25 and 75% (CV), demonstrating that the association of microorganisms is beneficial in the limiting water situation.(AU)

A mudança climática tem causado grandes mudanças nos fatores abióticos, sendo o estresse hídrico a maior ameaça à produção agrícola. As medidas destinadas a aliviar os problemas causados por este fator limitante de produção ocorreram através da adoção de estratégias sustentáveis, especialmente a biotecnologia microbiana, que utiliza as interações entre o microorganismo e a planta, garantindo a qualidade produtiva e induzindo a resistência da planta ao estresse biótico e abiótico. O objetivo do presente trabalho foi avaliar a fixação biológica de nitrogênio e o desenvolvimento de mudas de feijão, com co-inoculação de dois tipos de inoculantes, que foram submetidos ao estresse hídrico por diferentes capacidades de vaso. A experiência foi realizada em uma estufa, na Universidade Paranaense - UNIPAR, de abril a junho de 2019. O projeto experimental foi completamente randomizado (DIC), com 5 réplicas, 16 tratamentos e 80 unidades experimentais. A cultivar utilizada foi a SCS Riqueza. Os parâmetros avaliados foram a capacidade do vaso (25%, 50%, 75% e 90%); nódulos pequenos, grandes e totais, comprimento do rebento e da raiz, peso seco e fresco, carbono total e nitrogênio. A avaliação dos parâmetros morfológicos das mudas de feijão indicou que a técnica de co-inoculação promoveu efeitos benéficos para os parâmetros de massa seca do turião, nódulo e raiz. A análise da porcentagem de carbono e nitrogênio nos tecidos das mudas proporcionou um aumento na concentração destes elementos nos tratamentos que envolveram a co-inoculação (Azospirillum brasilensis e Rhizobium tropici) com capacidades de vaso de 25 e 75% (CV), demonstrando que a associação de microorganismos é benéfica na situação limite da água.(AU)

El cambio climático ha provocado importantes cambios en los factores abióticos, siendo el estrés hídrico la mayor amenaza para la producción agrícola. Las medidas encaminadas a paliar los problemas causados por este factor limitante de la producción se han producido mediante la adopción de estrategias sostenibles, especialmente la biotecnología microbiana, que utiliza las interacciones entre el microorganismo y la planta, asegurando la calidad productiva e induciendo la resistencia de la planta a los estreses bióticos y abióticos. El objetivo del presente trabajo fue evaluar la fijación biológica de nitrógeno y el desarrollo de plántulas de frijol, con la co-inoculación de dos tipos de inoculantes, que fueron sometidos a estrés hídrico por diferentes capacidades de maceta. El experimento se realizó en un invernadero, en la Universidade Paranaense - UNIPAR, de abril a junio de 2019. El diseño experimental fue completamente al azar (DIC), con 5 repeticiones, 16 tratamientos y 80 unidades experimentales. El cultivar utilizado fue SCS Riqueza. Los parámetros evaluados fueron capacidad de maceta (25%, 50%, 75% y 90%); nódulos pequeños, grandes y totales, longitud de brotes y raíces, peso seco y fresco, carbono y nitrógeno total. La evaluación de los parámetros morfológicos de las plántulas de frijol indicó que la técnica de coinoculación promovió efectos beneficiosos para los parámetros de masa seca de brotes, nódulos y raíces. El análisis del porcentaje de carbono y nitrógeno en los tejidos de las plántulas proporcionó un aumento en la concentración de estos elementos en los tratamientos que involucraron la coinoculación (Azospirillum brasilensis y Rhizobium tropici) con capacidades de maceta de 25 y 75% (CV), demostrando que la asociación de microorganismos es beneficiosa en la situación de agua limitante.(AU)

Multiple Effect of Different Plant Growth Promoting Microorganisms on Beans (Phaseolus vulgaris L. ) Crop

Abstract We evaluated the effect of combined Rhizobium tropici, Trichoderma asperellum and plant growth-promoting rhizobacteria (PGPR) in beans crop. The hypothesis that strains of T. asperullum, R. tropici and PGPR combined could improve growth, biomass accumulation and beans yield was tested under greenhouse and field conditions. The treatments consisted of control, mineral nitrogen application and inoculation, isolated and associated with the following microorganisms: Rhizobium tropici, Bacillus subtilis, Trichoderma asperellum and Burkholderia sp. 10N6. Results were evaluated by shoot dry weight (SDW) and root dry weight (RDW), number of nodules and yield components. In greenhouse environment all the microorganisms behaved similarly, and the treatments inoculated with Burkholderia sp. 10N6 (IBu) and R. tropici (IR) stood out regarding the production components. In field conditions the treatments IR and IRTBa presented the highest values of SDW and RDW. Our results suggest that inoculation with R. tropici, T. asperellum and PGPR may promote beans growth and bring benefits to shoot and root accumulation, increase the number of nodules as well as improve yield components, contributing to a sustainable agriculture.

Respuesta del simbiosistema frijol (Phaseolus vulgaris L.) y Rhizobium tropici CIAT899 ante el efecto alelopático de Ipomoea purpurea L. Roth / Responses of the common bean (Phaseolus vulgaris L.) and Rhizobium tropici CIAT899 symbiosystem to induced allelopathy by Ipomoea purpurea L. Roth

La alelopatía es un fenómeno que involucra la producción de metabolitos secundarios que influyen en el crecimiento de las plantas, pero este potencial alelopático ha sido poco estudiado en la simbiosis rizobio-leguminosa. Esta investigación tuvo los siguientes objetivos: 1) evaluar el potencial alelopático de lixiviados acuosos de Ipomoea purpurea L. Roth en la germinación de semillas y en el crecimiento radical de plántulas de frijol (Phaseolus vulgaris L.); 2) determinar el efecto de estos lixiviados en el crecimiento in vitro de Rhizobium tropici CIAT899, y 3) evaluar el potencial alelopático de I. purpurea en el crecimiento, la fisiología y la nodulación de frijol en simbiosis con R. tropici. Tanto el lixiviado acuoso de raíz como el de la parte aérea de I. purpurea estimularon la germinación de semillas de frijol y la elongación radical. El crecimiento in vitro de R. tropici fue inhibido al aplicar los 2 tipos de lixiviado. La presencia de I. purpurea tuvo un efecto negativo en el crecimiento y en las respuestas fisiológicas de las plantas de frijol, que fue atenuado cuando las plantas fueron inoculadas con Rhizobium tropici; no obstante, la nodulación asociada a esta bacteria fue afectada en presencia de la planta alelopática. Los resultados indican que la simbiosis de rizobios en las raíces de frijol es un elemento importante en la atenuación de los danos producidos por la planta alelopática I. purpurea.

Allelopathy is a phenomenon that involves the production of secondary metabolites that influence the growth of plants and microorganisms; however, this alellopathic effect has been scarcely studied on the rhizobia-legume symbiosis. The aims of this research were 1) to assess the allelopathic potential of aqueous extracts of Ipomoea purpurea L. Roth on seed germination and root length of common bean seedlings (Phaseolus vulgaris L.), 2) to determine its effects on the in vitro growth of Rhizobium tropici CIAT899, and 3) to evaluate the allelopathic potential of I. purpurea on the growth, nodulation and physiology of common bean plants inoculated with R. tropici. After 48 h, 15% of the aqueous root extract of I. purpurea stimulated seed germination, whereas 4% of the aqueous shoot extracts stimulated such germination. Both the root or shoot extracts stimulated seed germination and e root length. In vitro growth of R. tropici was inhibited as a result of the application of both aqueous extracts. The presence of I. purpurea negatively affected both the growth and physiological responses of common bean plants, and this effect was attenuated after the inoculation of R. tropici; nevertheless, this allelopathic plant affected root nodulation. Our results suggest that the symbiosis of rhizobia and roots of common bean plants is an important element for attenuating the negative effects caused by the allelopathic plant.

Initial pH of medium affects organic acids production but do not affect phosphate solubilization

The pH of the culture medium directly influences the growth of microorganisms and the chemical processes that they perform. The aim of this study was to assess the influence of the initial pH of the culture medium on the production of 11 low-molecular-weight organic acids and on the solubilization of calcium phosphate by bacteria in growth medium (NBRIP). The following strains isolated from cowpea nodules were studied: UFLA03-08 (Rhizobium tropici), UFLA03-09 (Acinetobacter sp.), UFLA03-10 (Paenibacillus kribbensis), UFLA03-106 (Paenibacillus kribbensis) and UFLA03-116 (Paenibacillus sp.). The strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 solubilized Ca3(PO4)2 in liquid medium regardless of the initial pH, although without a significant difference between the treatments. The production of organic acids by these strains was assessed for all of the initial pH values investigated, and differences between the treatments were observed. Strains UFLA03-09 and UFLA03-10 produced the same acids at different initial pH values in the culture medium. There was no correlation between phosphorus solubilized from Ca3(PO4)2 in NBRIP liquid medium and the concentration of total organic acids at the different initial pH values. Therefore, the initial pH of the culture medium influences the production of organic acids by the strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 but it does not affect calcium phosphate solubilization.