Insights into Circular Horticulture: Knowledge Diffusion, Resource Circulation, One Health Approach, and Greenhouse Technologies.

The integration of the circular economy in agriculture has promoted sustainable innovation in food production systems such as horticulture. The present paper illustrates how horticulture is transitioning to the circular economy. This research field's performance approaches and trends were assessed through a bibliometric and text-mining analysis of the literature. Our findings revealed that circular horticulture is a recent research field that is constantly growing. Its approach has been neither systemic nor integrative but fragmented. Bioeconomy, urban agriculture, recycled nutrients, biochar, fertigation, and desalination have been positioned as research hotspots. Vegetables and fruits are the most studied crops. Resource circulation has focused primarily on biowaste recovery to provide benefits such as biofertilizers and linear-substrate substitutes, and on water reuse for the establishment of hydroponic systems. The One Health approach is scarcely explored and, therefore, weakly articulated, wherein the absence of assessment methodologies encompassing the health of ecosystems, animals, and people is a notable limitation. Science-policy interfaces between One Health and food systems need to be improved. Lastly, greenhouse technologies are aligned with bioenergy, sustainable materials, and sensing technologies. Challenges and directions for future research have been raised to promote the redesign of horticultural production systems, integrating long-term circularity.

Dry-Caribbean Bacillus spp. Strains Ameliorate Drought Stress in Maize by a Strain-Specific Antioxidant Response Modulation.

Drought is a global problem for crop productivity. Therefore, the objective of this research was to evaluate five dry-Caribbean Bacillus spp. strains in drought stress amelioration in maize plants. Maize seeds were single-strain inoculated and sown in pots under greenhouse conditions. After 12 days, plants were subjected to 33 days of drought conditions, i.e., 30% of soil field capacity, and then collected to measure leaf and root dry biomass, plant height, antioxidant enzymes, proline accumulation, and P+, Ca2+, and K+ uptake. Results correlated drought stress amelioration with the inoculation of Bacillus spp. strains XT13, XT38 and XT110. Inoculated plants showed increases in dry biomass, plant height, and K+ and P+ uptake. The overall maize antioxidant response to bacterial inoculation under drought stress showed dependence on proline accumulation and decreases in ascorbate peroxidase and glutathione reductase activities. Moreover, results suggest that this stress amelioration is driven by a specific plant-strain correlation observed in antioxidant response changes in inoculated plants under stress. Also, there is a complex integration of several mechanisms, including plant growth-promotion traits and nutrient uptake. Hence, the use of dry-Caribbean plant growth-promoting Bacillus strains represents an important biotechnological approach to enhance crop productivity in arid and semi-arid environments.

Plant growth promoting rhizobacteria and their potential as bioinoculants on Pennisetum clandestinum (Poaceae)

Introduction: The sustainable production of pastures has become a fundamental challenge for the livestock sector where research with plant growth-promoting rhizobacteria as a viable solution, has nearly not been reported. Objective: In this study, we aimed to examine the potential to stimulate growth in Pennisetum clandestinum grass using four isolated bacterial strains from soils obtained from a Colombian tropical silvopastoral system. Methods: We previously identified genetically the strains and characterized two plant growth promoting activities. In addition, we evaluated the growth-promoting effect of the strains in Kikuyo grass under greenhouse conditions. Results: We found that the four bacterial strains were phylogenetically associated with Klebsiella sp. (strains 28P and 35P), Beijerinka sp. (37L) and Achromobacter xylosoxidans (E37), based on partial 16S rRNA gene sequencing. Moreover, the in vitro biochemical assays demonstrated that the strains exhibited some plant growth promoting mechanisms such as 1-aminocyclopropane-1-carboxylic acid deaminase activity and indole compound synthesis. Notably, bacterial inoculation under greenhouse conditions showed a positive influence on P. clandestinum growth. We found a significant (P < 0.05) effect on root and shoot length and shoot dry weight. Shoot length increased by 52 % and 30 % with 37L and 35P compared to those without inoculation treatment. Similarly, the use of 37L and 28P raised shoot dry weight values by 170 % and 131 %, respectively. In root development, inoculation with strains 37L and E37 increased root length by 134 % and 100 %, respectively. Conclusion: Beijerinckia sp. 37L was the most effective of the four strains at increasing P. clandestinum biomass and length.

Introducción: La producción sostenible de pastos se ha convertido en un desafío fundamental para el sector ganadero, donde investigaciones con bacterias promotoras de crecimiento vegetal, como una solución viable, han sido poco reportadas. Objetivo: El objetivo de este estudio fue examinar el potencial para estimular el crecimiento del pasto Pennisetum clandestinum utilizando cuatro cepas bacterianas aisladas de suelos obtenidos de un sistema silvopastoril tropical colombiano. Métodos: Anteriormente identificamos genéticamente las cepas y caracterizamos dos actividades que promueven el crecimiento de las plantas. Además, evaluamos el efecto promotor del crecimiento de las cepas en el pasto Kikuyo en condiciones de invernadero. Resultados: Encontramos que las cuatro cepas bacterianas se asociaron filogenéticamente con Klebsiella sp. (cepas 28P y 35P), Beijerinka sp. (37L) y Achromobacter xylosoxidans (E37), basados en la secuenciación parcial del gen 16S rRNA. Además, los ensayos bioquímicos in vitro demostraron que las cepas exhibían algunos mecanismos que promueven el crecimiento de las plantas tales como la actividad de la enzima desaminasa del ácido 1-aminociclopropano-1- carboxílico, y la síntesis del compuesto indol. En particular, la inoculación bacteriana bajo condiciones de invernadero mostró una influencia positiva en el crecimiento de P. clandestinum. Encontramos un efecto significativo (P < 0.05) en la longitud de la raíz y el tallo, y el peso seco del tallo. La longitud del tallo aumentó en un 52 % y 30 % con 37L y 35P, respectivamente, en comparación con aquellos sin tratamiento de inoculación. Igualmente, el uso de las cepas 37L y 28P aumentó los valores de peso seco del tallo en un 170 y un 131 %, respectivamente. En el desarrollo de la raíz, la inoculación con las cepas 37L y E37 aumentó la longitud de la raíz en 134 y 100 %, respectivamente. Conclusión: Beijerinckia sp. 37L fue la más efectiva de las cuatro cepas al aumentar la biomasa y la longitud de P. clandestinum.

Azotobacter chroococcum as a potentially useful bacterial biofertilizer for cotton (Gossypium hirsutum): Effect in reducing N fertilization / Azotobacter chroococcum como biofertilizante bacteriano potencialmente útil para el algodón (Gossypium hirsutum L.): efecto en la reducción de la fertilización nitrogenada

The aim of this research was to evaluate whether the application of two plant growth-promoting (rhizo)bacteria might reduce nitrogen fertilization doses in cotton. We used strains Azotobacter chroococcum AC1 and AC10 for their proven ability to promote seed germination and cotton growth. These microorganisms were characterized by their plant growth-promoting activities. Then, we conducted a glasshouse study to evaluate the plant growth promoting ability of these strains with reduced doses of urea fertilization in cotton. Results revealed that both strains are capable of fixing nitrogen, solubilizing phosphorus, synthesizing indole compounds and producing hydrolytic enzymes. After 12 weeks, the glasshouse experiment showed that cotton growth was positively influenced due to bacterial inoculation with respect to chemical fertilization. Notably, we observed that microbial inoculation further influenced plant biomass (p<0.05) than nitrogen content. Co-inoculation, interestingly, exhibited a greater beneficial effect on plant growth parameters compared to single inoculation. Moreover, similar results without significant statistical differences were observed among bacterial co-inoculation plus 50% urea and 100% fertilization. These findings suggest that coinoculation of A. chroococcum strains allow to reduce nitrogen fertilization doses up to 50% on cotton growth. Our results showed that inoculation with AC1 and AC10 represents a viable alternative to improve cotton growth while decreasing the N fertilizer dose and allows to alleviate the environmental deterioration related to N pollution.

El objetivo de esta investigación fue evaluar si la aplicación de 2 (rizo)bacterias promotoras del crecimiento vegetal podría reducir la dosis de fertilizante nitrogenado en el cultivo de algodón. Se usaron las cepas Azotobacter chroococcum AC1 y AC10 por su habilidad para promover la germinación de semillas y el crecimiento del algodonero. Estos microorganismos fueron caracterizados sobre la base de sus actividades de promoción del crecimiento vegetal. Luego se realizó un estudio de invernadero con plantas de algodón para evaluar la capacidad de promoción del crecimiento vegetal de dichas cepas con dosis reducidas de urea. Los resultados revelaron que ambas cepas son capaces de fijar nitrógeno, solubilizar fósforo, sintetizar compuestos indólicos y producir enzimas hidrolíticas. Después de 12 semanas, el experimento de invernadero permitió observar que el crecimiento del algodón fue influido positivamente por la inoculación bacteriana con respecto a la fertilización química. En particular, se evidenció que la inoculación microbiana impactó más en la biomasa vegetal (p<0,05) que en el contenido de nitrógeno. Curiosamente, la coinoculación exhibió un mayor efecto positivo sobre los parámetros de crecimiento en comparación con la inoculación simple. Además, se observaron resultados similares, sin diferencias estadísticamente significativas, entre la coinoculación bacteriana más del 50% de urea y el 100% de fertilización. Estos hallazgos indican que la coinoculación de las cepas de A. chroococcum AC1 y AC10 permitiría reducir las dosis de fertilización nitrogenada del cultivo de arroz en hasta el 50% y aliviar, de esta manera, el deterioro ambiental relacionado con la contaminación por N.

Azotobacter chroococcum as a potentially useful bacterial biofertilizer for cotton (Gossypium hirsutum): Effect in reducing N fertilization.

The aim of this research was to evaluate whether the application of two plant growth-promoting (rhizo)bacteria might reduce nitrogen fertilization doses in cotton. We used strains Azotobacter chroococcum AC1 and AC10 for their proven ability to promote seed germination and cotton growth. These microorganisms were characterized by their plant growth-promoting activities. Then, we conducted a glasshouse study to evaluate the plant growth promoting ability of these strains with reduced doses of urea fertilization in cotton. Results revealed that both strains are capable of fixing nitrogen, solubilizing phosphorus, synthesizing indole compounds and producing hydrolytic enzymes. After 12 weeks, the glasshouse experiment showed that cotton growth was positively influenced due to bacterial inoculation with respect to chemical fertilization. Notably, we observed that microbial inoculation further influenced plant biomass (p<0.05) than nitrogen content. Co-inoculation, interestingly, exhibited a greater beneficial effect on plant growth parameters compared to single inoculation. Moreover, similar results without significant statistical differences were observed among bacterial co-inoculation plus 50% urea and 100% fertilization. These findings suggest that co-inoculation of A. chroococcum strains allow to reduce nitrogen fertilization doses up to 50% on cotton growth. Our results showed that inoculation with AC1 and AC10 represents a viable alternative to improve cotton growth while decreasing the N fertilizer dose and allows to alleviate the environmental deterioration related to N pollution.

Desarrollo de un sistema de fermentación líquida y de enquistamiento para una bacteria fijadora de nitrógeno con potencial como biofertilizante / Development of a liquid fermentation system and encystment for a nitrogen-fixing bacterium strain having biofertilizer potential

El uso indiscriminado de fertilizantes químicos ha contribuido al deterioro de las propiedades biológicas, físicas y químicas del suelo, lo que derivó en la pérdida de su capacidad productiva. Por esta razón, se ha planteado como alternativa tecnológica el uso de biofertilizantes. El objetivo de esta investigación fue desarrollar un sistema de fermentación líquida y de enquistamiento adecuado para la multiplicación de Azotobacter chroococcum cepa AC1, una bacteria utilizada en la formulación de un biofertilizante actualmente producido por CORPOICA, Colombia. Se emplearon diseños estadísticos secuenciales para determinar las condiciones del sistema de fermentación. Se evaluaron la interacción entre la agitación, la aireación y el pH sobre la biomasa viable obtenida de AC1 (UFC/ml), que se tomó como variable de respuesta. Además, se evaluó la capacidad de enquistamiento de esta bacteria empleando 2 agentes de enquistamiento, AE01 y AE02. La actividad potencial promotora del crecimiento vegetal fue evaluada por medio del ensayo de ARA (fijación biológica de nitrógeno), la técnica de azul de fosfomolibdeno (solubilización de fosfato) y la reacción colorimétrica empleando el reactivo de Salkowski (producción de compuestos indólicos). Se evidenciaron efectos significativos (p <0,05) sobre la producción de biomasa de los 3 factores evaluados (pH, aireación y agitación) individualmente, de una interacción dual y en la interacción tripartita, teniendo un efecto positivo sobre la variable de respuesta la aireación y agitación. La adición de los inductores de enquistamiento AE01 y AE02 demostró la capacidad de la cepa AC1 para formar quistes en condiciones de estrés. Asimismo, las condiciones de fermentación y el enquistamiento no afectaron las actividades biológicas evaluadas.

The indiscriminate use of chemical fertilizers has contributed to the deterioration of the biological, physical and chemical properties of the soil, resulting in the loss of its productive capacity. For this reason, the use of biofertilizers has emerged as a technological alternative. The objective of this research was to develop a suitable liquid fermentation system and encystment for the multiplication of Azotobacter chroococcum AC1 strain, a bacterium employed in a biofertilizer formulation produced at present by CARPOICA, Colombia. Sequential statistical designs were used to determine the conditions in the fermentation system. The interaction between agitation, aeration and pH was evaluated on the viable biomass (CFU/ml) of AC1. In addition, the encystment ability of the strain was evaluated using two encystment agents and the potential plant growth-promoting rhizobacteria (PGPR) activity was assessed by different techniques, such as nitrogen fixation by ARA, phosphate solubilization by the phospho-molybdenum-blue reaction and indolic compound production by colorimetric reaction using the Salkowski reagent. Results showed significant effects (p <0.05) on the viable biomass in the three conditions (pH, aeration and agitation) tested individually, in one dual interaction and one tripartite interaction, were demonstrated to have a positive effect on the response variable aeration and agitation. The addition of the two encystment agents evaluated, AE01 and AE02, demonstrated the ability of AC1 to form cysts under stress conditions. Likewise, fermentation and encystment conditions did not affect the biological activities tested.

[Development of a liquid fermentation system and encystment for a nitrogen-fixing bacterium strain having biofertilizer potential]. / Desarrollo de un sistema de fermentación líquida y de enquistamiento para una bacteria fijadora de nitrógeno con potencial como biofertilizante.

The indiscriminate use of chemical fertilizers has contributed to the deterioration of the biological, physical and chemical properties of the soil, resulting in the loss of its productive capacity. For this reason, the use of biofertilizers has emerged as a technological alternative. The objective of this research was to develop a suitable liquid fermentation system and encystment for the multiplication of Azotobacter chroococcum AC1 strain, a bacterium employed in a biofertilizer formulation produced at present by CARPOICA, Colombia. Sequential statistical designs were used to determine the conditions in the fermentation system. The interaction between agitation, aeration and pH was evaluated on the viable biomass (CFU/ml) of AC1. In addition, the encystment ability of the strain was evaluated using two encystment agents and the potential plant growth-promoting rhizobacteria (PGPR) activity was assessed by different techniques, such as nitrogen fixation by ARA, phosphate solubilization by the phospho-molybdenum-blue reaction and indolic compound production by colorimetric reaction using the Salkowski reagent. Results showed significant effects (p<0.05) on the viable biomass in the three conditions (pH, aeration and agitation) tested individually, in one dual interaction and one tripartite interaction, were demonstrated to have a positive effect on the response variable aeration and agitation. The addition of the two encystment agents evaluated, AE01 and AE02, demonstrated the ability of AC1 to form cysts under stress conditions. Likewise, fermentation and encystment conditions did not affect the biological activities tested.

Efecto de rizobacterias promotoras de crecimiento vegetal solubilizadoras de fosfato en Lactuca sativa cultivar White Boston / Effect of plant growth promoting rhizobacteria phosate solubilizing Lactuca sativa cultivar White Boston

En las últimas décadas, la agricultura colombiana se ha visto afectada por la reducción de la productividad en las zonas hortícolas, el incremento de los costos de producción y la dependencia del uso de productos químicos, produciendo un daño irreversible al medio ambiente y la calidad de vida de productores y consumidores. El objetivo de investigación fue evaluar el efecto de rizobacterias promotoras del crecimiento vegetal del género Pseudomonas sp. sobre Lactuca sativa cultivar White Boston como solubilizadoras de roca fosfórica. El estudio se realizó en el Centro de Investigación Tibaitatá (Corpoica) ubicado en Mosquera (Cundinamarca-Colombia). Los resultados demostraron que las cepas tienen la capacidad intrínseca para solubilizar fuentes de fósforo de baja solubilidad como la roca fosfórica. La aplicación de inoculantes con base en las cepas: Pseudomonas fluorescens FR1, Pseudomonas sp., UVLO27 y Pseudomonas sp. LEAV18 arrojaron los mejores resultados. Las cepas Pseudomonas sp. FR2, UVLO27 y K35, tienen la capacidad de producir índoles y sideróforos. El experimento en invernadero evidenció que las cepas Pseudomonas fluorescens FR1, Pseudomonas sp. FR2 y UVLO27 incrementaron de manera significativa (P<0.05) la biomasa y el desarrollo de las plantas. El uso de rocas fosfóricas representa una alternativa económica y ecológica viable, en sistemas de agricultura sostenible.

In the last decades, Colombian agriculture has been affected by the reduction in productivity in horticultural areas, increase in production costs and the dependence of chemical products usage, causing and irreversible damage to environment and producers and consumers life quality. The aim of this research was to evaluate the effect of plant growth promoting rhizobacteria of the genus Pseudomonas sp. under Lactuca sativa cultivar White Boston as phosphate rock solubilizing bacteria. The study took place in the Research Centre Tibaitatá-Corpoica, located in Mosquera (Cundinamarca-Colombia). Results demonstrated that the strains have an intrinsic capacity to solubilize low solubility phosphorus sources as phosphate rock. Inoculants application based on: Pseudomonas fluorescensFR1, Pseudomonas sp., UVLO27 and Pseudomonas sp. LEAV18 strains displayed the best results. The strains Pseudomonas sp. FR2, UVLO27 and K35, are capable of producing indoles and siderophores. The green house experiment showd that strain Pseudomonas fluorescens FR1, Pseudomonas sp. FR2 of phosphate rocks represents a viable economic and ecological alternative in sustainable agriculture systems.