Composites Based on Eucalyptus Nitens Leaves and Natural Rubber as a Valuable Alternative for the Development of Elastomeric Materials with Low Microbiological Impact.

The forest industry produces several low-value by-products, such as bark, sawdust, limbs, and leaves, that are not ultimately disposed of and remain in the forests and sawmill facilities. Among these by-products are leaves, which contain not only cellulose fibers and lignin but also essential oils such as terpenes. These are biosynthesized in a similar way as cis-1,4-polyisoprene. In this context, this work evaluates the use of screened and unscreened dried Eucalyptus nitens leaves in natural rubber. Among the most relevant results of this work is a significant increase in mechanical properties, such as tensile strength and elongation at break, reaching values of 9.45 MPa and 649% of tensile strength and elongation at break, respectively, for a sample of natural rubber containing sieved dried leaves of Eucalyptus nitens. In addition, it is observed that the content of this vegetable filler allows for inhibiting the antibacterial effect of vulcanized rubber against several bacteria, such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli K 12, Escherichia coli FT 17 and Pseudomonas fluorescens. These results are promising because they not only add value to a by-product of the forestry industry, improving the mechanical properties of natural rubber from a sustainable approach but also increase the affinity of rubber with bacterial microorganisms that may play a role in certain ecosystems.

Transcriptome Dynamics of Rooting Zone and Leaves during In Vitro Adventitious Root Formation in Eucalyptus nitens.

Wood properties and agronomic traits associated with fast growth and frost tolerance make Eucalyptus nitens a valuable forest alternative. However, the rapid age-related decline in the adventitious root (AR) formation (herein, meaning induction, initiation, and expression stages) limits its propagation. We analyzed transcriptomic profile variation in leaves and stem bases during AR induction of microcuttings to elucidate the molecular mechanisms involved in AR formation. In addition, we quantified expressions of candidate genes associated with recalcitrance. We delimited the ontogenic phases of root formation using histological techniques and Scarecrow and Short-Root expression quantification for RNA sequencing sample collection. We quantified the gene expressions associated with root meristem formation, auxin biosynthesis, perception, signaling, conjugation, and cytokinin signaling in shoots harvested from 2- to 36-month-old plants. After IBA treatment, 702 transcripts changed their expressions. Several were involved in hormone homeostasis and the signaling pathways that determine cell dedifferentiation, leading to root meristem formation. In part, the age-related decline in the rooting capacity is attributable to the increase in the ARR1 gene expression, which negatively affects auxin homeostasis. The analysis of the transcriptomic variation in the leaves and rooting zones provided profuse information: (1) To elucidate the auxin metabolism; (2) to understand the hormonal and signaling processes involved; (3) to collect data associated with their recalcitrance.

Genome sequencing of oomycete isolates from Chile supports the New Zealand origin of Phytophthora kernoviae and makes available the first Nothophytophthora sp. genome.

Genome sequences were generated for six oomycete isolates collected from forests in Valdivia, Chile. Three of the isolates were identified morphologically as Phytophthora kernoviae, whereas two were similar to other clade 10 Phytophthora species. One isolate was tentatively identified as Nothophytophthora valdiviana based on nucleotide sequence similarity in the cytochrome oxidase 1 gene. This is the first genome sequence for this recently described genus. The genome assembly was more fragmented and contained many duplicated genes when compared with the other Phytophthora sequences. Comparative analyses were performed with genomic sequences of the P. kernoviae isolates from the UK and New Zealand. Although the potential New Zealand origin of P. kernoviae has been suggested, new isolations from Chile had cast doubt on this hypothesis. We present evidence supporting P. kernoviae as having originated in New Zealand. However, investigation of the diversity of oomycete species in Chile has been limited and warrants further exploration. We demonstrate the expediency of genomic analyses in determining phylogenetic relationships between isolates within new and often scantly represented taxonomic groups, such as Phytophthora clade 10 and Nothophytophthora. Data are available on GenBank via BioProject accession number PRJNA352331.

Caracterización de rizobacterias promotoras de crecimiento en plántulas de Eucalyptus nitens / Characterization of growth-promoting rhizobacteria in Eucalyptus nitens seedlings

Se aislaron bacterias rizosféricas y endófitas a partir de rizósfera y tejidos de raíz de árboles de Eucalyptus nitens con el objetivo de evaluar su capacidad de promover el crecimiento en plántulas de la misma especie en condiciones de invernadero. Los aislamientos que incrementaron el crecimiento de las plántulas fueron identificados y caracterizados por su capacidad de producir ácido indolacético (AIA), solubilizar fosfato y expresar la 1-aminociclopropano-1-carboxilato (ACC) desaminasa. Los 105 aislamientos obtenidos fueron morfológicamente diferentes y solo 15 promovieron significativamente el crecimiento de plántulas de E. nitens. Los máximos incrementos observados fueron en el peso seco aéreo (142 %) y de la raíz (135 %); también aumentaron la altura de las plantas (50 %) y el largo de raíces (45 %) de las mismas. Las rizobacterias pertenecieron a los géneros Arthrobacter, Lysinibacillus, Rahnella y Bacillus. Los aislados identificados como A. phenanthrenivorans 21 y B. cereus 113 incrementaron la emergencia de E. nitens a los 12 días en un valor promedio de 3,15 veces con relación al control. R. aquatilis aislado 78 presentó la mayor producción de AIA (97,5 ± 2,87 μg/ml) en presencia de triptófano y el mayor índice de solubilización de fósforo (2,4). B. amyloliquefaciens aislado 60 fue positivo para la actividad ACC desaminasa. Los resultados obtenidos indican el potencial de las rizobacterias estudiadas como promotoras de emergencia y crecimiento de plántulas de E. nitens y su posible uso como inoculantes, ya que presentan más de un mecanismo de acción asociado a la promoción del crecimiento.(AU)

Rhizospheric and endophytic bacteria were isolated from the rizosphere and root tissue of Eucalyptus nitens. The objective of this work was to evaluate their capacity to promote growth in seedlings of the same species under greenhouse conditions. The isolates that improved seedling growth were identified and characterized by their capacity to produce indoleacetic acid (IAA), solubilize phosphates and increase 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. One hundred and five morphologically different strains were isolated, 15 of which promoted E. nitens seedling growth, significantly increasing the height (50%), root length (45%) as well as the aerial and root dry weight (142% and 135% respectively) of the plants. Bacteria belonged to the genus Arthrobacter, Lysinibacillus, Rahnella and Bacillus. Isolates A. phenanthrenivorans 21 and B. cereus 113 improved 3.15 times the emergence of E. nitens after 12 days, compared to control samples. Among isolated R. aquatilis, 78 showed the highest production of IAA (97.5±2.87 μg/ml) in the presence of tryptophan and the highest solubilizer index (2.4) for phosphorus, while B. amyloliquefaciens 60 isolate was positive for ACC deaminase activity. Our results reveal the potential of the studied rhizobacteria as promoters of emergence and seedling growth of E. nitens, and their possible use as PGPR inoculants, since they have more than one mechanism associated with plant growth promotion.(AU)

Caracterización de rizobacterias promotoras de crecimiento en plántulas de Eucalyptus nitens / Characterization of growth-promoting rhizobacteria in Eucalyptus nitens seedlings

Se aislaron bacterias rizosféricas y endófitas a partir de rizósfera y tejidos de raíz de árboles de Eucalyptus nitens con el objetivo de evaluar su capacidad de promover el crecimiento en plántulas de la misma especie en condiciones de invernadero. Los aislamientos que incrementaron el crecimiento de las plántulas fueron identificados y caracterizados por su capacidad de producir ácido indolacético (AIA), solubilizar fosfato y expresar la 1-aminociclopropano-1-carboxilato (ACC) desaminasa. Los 105 aislamientos obtenidos fueron morfológicamente diferentes y solo 15 promovieron significativamente el crecimiento de plántulas de E. nitens. Los máximos incrementos observados fueron en el peso seco aéreo (142 %) y de la raíz (135 %); también aumentaron la altura de las plantas (50 %) y el largo de raíces (45 %) de las mismas. Las rizobacterias pertenecieron a los géneros Arthrobacter, Lysinibacillus, Rahnella y Bacillus. Los aislados identificados como A. phenanthrenivorans 21 y B. cereus 113 incrementaron la emergencia de E. nitens a los 12 días en un valor promedio de 3,15 veces con relación al control. R. aquatilis aislado 78 presentó la mayor producción de AIA (97,5 ± 2,87 μg/ml) en presencia de triptófano y el mayor índice de solubilización de fósforo (2,4). B. amyloliquefaciens aislado 60 fue positivo para la actividad ACC desaminasa. Los resultados obtenidos indican el potencial de las rizobacterias estudiadas como promotoras de emergencia y crecimiento de plántulas de E. nitens y su posible uso como inoculantes, ya que presentan más de un mecanismo de acción asociado a la promoción del crecimiento.

Rhizospheric and endophytic bacteria were isolated from the rizosphere and root tissue of Eucalyptus nitens. The objective of this work was to evaluate their capacity to promote growth in seedlings of the same species under greenhouse conditions. The isolates that improved seedling growth were identified and characterized by their capacity to produce indoleacetic acid (IAA), solubilize phosphates and increase 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. One hundred and five morphologically different strains were isolated, 15 of which promoted E. nitens seedling growth, significantly increasing the height (50%), root length (45%) as well as the aerial and root dry weight (142% and 135% respectively) of the plants. Bacteria belonged to the genus Arthrobacter, Lysinibacillus, Rahnella and Bacillus. Isolates A. phenanthrenivorans 21 and B. cereus 113 improved 3.15 times the emergence of E. nitens after 12 days, compared to control samples. Among isolated R. aquatilis, 78 showed the highest production of IAA (97.5±2.87 μg/ml) in the presence of tryptophan and the highest solubilizer index (2.4) for phosphorus, while B. amyloliquefaciens 60 isolate was positive for ACC deaminase activity. Our results reveal the potential of the studied rhizobacteria as promoters of emergence and seedling growth of E. nitens, and their possible use as PGPR inoculants, since they have more than one mechanism associated with plant growth promotion.

[Characterization of growth-promoting rhizobacteria in Eucalyptus nitens seedlings]. / Caracterización de rizobacterias promotoras de crecimiento en plántulas de Eucalyptus nitens.

Rhizospheric and endophytic bacteria were isolated from the rizosphere and root tissue of Eucalyptus nitens. The objective of this work was to evaluate their capacity to promote growth in seedlings of the same species under greenhouse conditions. The isolates that improved seedling growth were identified and characterized by their capacity to produce indoleacetic acid (IAA), solubilize phosphates and increase 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. One hundred and five morphologically different strains were isolated, 15 of which promoted E. nitens seedling growth, significantly increasing the height (50%), root length (45%) as well as the aerial and root dry weight (142% and 135% respectively) of the plants. Bacteria belonged to the genus Arthrobacter, Lysinibacillus, Rahnella and Bacillus. Isolates A. phenanthrenivorans 21 and B. cereus 113 improved 3.15 times the emergence of E. nitens after 12 days, compared to control samples. Among isolated R. aquatilis, 78 showed the highest production of IAA (97.5±2.87 µg/ml) in the presence of tryptophan and the highest solubilizer index (2.4) for phosphorus, while B. amyloliquefaciens 60 isolate was positive for ACC deaminase activity. Our results reveal the potential of the studied rhizobacteria as promoters of emergence and seedling growth of E. nitens, and their possible use as PGPR inoculants, since they have more than one mechanism associated with plant growth promotion.