Effect of sowing date and water availability on growth of plants of chia (Salvia hispanica L) established in Chile.

From 2010 to 2014 two trials were performed to assess the effect of sowing date (SD1, SD2) and irrigation treatments (IT1, IT2) on the growth of chia in central Chile, measuring leaf area (LA) and dry matter (DM) as primary parameters and relative growth rate (RGR), net assimilation rate (NAR), leaf weight ratio (LWR), crop growth rate (CGR) and specific leaf weight (SLW) as secondary parameters. Both LA and DM reached maximum values between 640 and 1150 accumulated degree days (ADD). However, LA and DM were 25% greater for sowing dates than for available water. Flowering date was also not affected by sowing date or water availability; plants flowered at 1140 and 942 ADD in SD1 and SD2 respectively, and at 499 ADD in the water availability trial. Sowing date had a significant effect on RGR 0.15 g g-1 d-1 for SD1 and 0.12 g g-1 d-1 for SD2 at 410 ADD. Greater water availability increased RGR by 60% compared to stressed plants, however NAR was similar between sowing dates with a tendency to greater values in SD2 plants; maximum values were recorded at 514 ADD in IT1 and IT2, with a tendency toward higher values in IT1. Thus, the primary growth variables LA, DM and flowering are genetically determined. However, the derived growth variables RGR, LWR, NAR, CGR and SLW were affected by sowing date and water availability, with significant differences at p≤ 0.05. The results showed that the sowing date and water availability influence significantly the growth parameters. The physiological component (NAR) show a strong influence on the growth rate of the chia (RGR), above the morphological component (SLW and LAR).

Fuentes naturales de fitoesteroles y factores de producción que lo modifican / Natural sources of phytosterols and production factors that modify them

Actualmente los fitoesteroles son adicionados a los alimentos industrializados, lo que aumenta su costo y por lo tanto limita su consumo. Este manuscrito tiene como objetivo identificar alimentos que son una fuente natural de fitoesteroles, así como también analizar cómo el ambiente y el manejo productivo modifican su contenido, relacionando estos aspectos con la salud. Los fitoesteroles son compuestos presentes en las plantas con propiedades hipocolesterolémicas, que pueden contribuir a prevenir las enfermedades cardiovasculares. La ingesta diaria estimada de fitoesteroles varía entre 160 y 500 mg/día, sin embargo su acción beneficiosa se logra con consumos de 1500 mg a 2400 mg diarios. Las semillas de oleaginosas y de cereales son las mayores fuentes naturales de fitoesteroles. El amaranto es considerado un pseudocereal y entre los cereales tiene la mayor concentración de fitoesteroles con 178 mg/100 g, valor 5 veces superior al de la harina de trigo. El ambiente modifica el contenido de fitoesteroles de los alimentos, la sequía y temperaturas altas duplican su contenido en las semillas; la fertilización nitrogenada y la fecha de siembra pueden provocar cambios, pero se requieren más estudios al respecto. La selección de genotipos con mayor contenido de fitoesteroles y el estudio de la interacción genotipo ambiente, permitirá la identificación de aquellos genotipos con adaptación local para este carácter. El manejo productivo podrá aumentar la oferta de alimentos naturales ricos en fitoesteroles, contribuyendo a una mayor oferta de alimentos protectores de la salud(AU)

Currently phytosterols are added to processed foods, which increase their cost and therefore limits its use. This manuscript aims to identify foods that are a natural source of phytosterols, as well as analyze how the environment and production management modify its content, linking these aspects with health. Phytosterols are compounds found in plants with hypocholesterolemic properties, which may help prevent cardiovascular diseases. The estimated daily intake of phytosterols varies between 160 and 500 mg/day, but its beneficial effect is achieved with 1,500 to 2,400 mg daily consumption. Oil and cereal seeds are the largest natural sources of phytosterols. Amaranth is considered a pseudocereal and among the cereals has the highest concentration of phytosterols with 178 mg/100 g, value 5 times higher than wheat flour. Environment modifies phytosterol content in food, drought and high temperatures can double their content in seeds; nitrogen fertilization and planting date can cause changes, but more studies are needed. The selection of genotypes with higher phytosterol content and studying the genotype x environment interaction, allow the identification of those genotypes with local adaptation for this character. The production management will increase the supply of natural foods rich in phytosterols, contributing to a greater supply of health protective foods(AU)

Genetic diversity of Rhizobium from nodulating beans grown in a variety of Mediterranean climate soils of Chile.

In spite of potentially being an important source of rhizobial diversity and a key determinant of common bean productivity, there is a paucity of data on Rhizobium genetic variation and species composition in the important bean producing area of Chile and only one species has been documented (Rhizobium leguminosarum). In this study, 240 Rhizobium isolates from Torcaza bean (Phaseolus vulgaris L.) nodules established in the highest bean producing area in Chile (33°34'S-70°38'W and 37°36'S-71°47'W) were characterized by PCR-RFLP markers for nodC gene, revealing eight banding patterns with the polymorphic enzyme Hinf I. The locality of San Agustín de Aurora in Central Chile (35°32'S-71°29'W) had the highest level of diversity. Isolates were classified by species using PCR-RFLP markers for 16S rDNA gene and were confirmed by sequencing an internal fragment of the 16S rDNA gene. The results confirmed the presence of R. leguminosarum and three other species of rhizobia nodulating beans in South Central Chile (R. etli, R. tropici and R. leucaenae). R. tropici and R. leucaenae showed the least genetic variation and were most commonly identified in acid soils, while R. etli was the most common species in slightly acidic to moderately alkaline soils, with higher levels of organic matter content. R. leguminosarum was identified in almost all soils, was the most genetically diverse, and was the most common, being documented in soils with pH that ranged between 5.3 and 8.2, and with organic matter content between 2.1 and 4 %.

Gibberellin oxidase activities in Bradyrhizobium japonicum bacteroids.

Bradyrhizobium japonicum bacteroids isolated from root nodules of soybean (Glycine max.) plants converted the gibberellin (GA) precursor [(14)C1]GA12 into several products identified by combined gas chromatography-mass spectrometry as [(14)C1]GA24, [(14)C1]GA9, [(14)C1]GA15, GA9 17-nor-16-one and unidentified products. The oxidation of GA12, catalyzed by the GA 20-oxidase, was present in symbiotic bacteroids from plants around flowering, but not in bacteroids from plants at either an early vegetative stage or at late growth stages. Expression of cps and ks genes, involved in ent-kaurene biosynthesis, was also demonstrated in bacteroids from soybean plants around flowering. Earlier precursors of the GA pathway, ent-[(14)C1]kaurenoic acid or [(14)C4]GA12-aldehyde, were efficiently utilized by B. japonicum bacteroids to give labelled GA9 plus intermediates partially oxidized at C-20, as well as GA9 17-nor-16-one and an unidentified product. No 3ß or 13-hydroxylated [(14)C]GAs were detected in any of the incubations. Moreover the C19-GAs [(14)C1]GA4 or [(14)C1]GA20 were recovered unconverted upon incubation with the bacteroids which supports the absence of GA 3ß-hydroxylase activity in B. japonicum. The bacterial 20-oxidase utilized the 13-hydroxylated substrates [(14)C1]GA53, [(14)C1]GA44 or [(14)C1]GA19, although with less efficiency than [(14)C1]GA12 to give [(14)C1]GA20 as final product, while the 3ß-hydroxylated substrate [(14)C1]GA14 was converted to [(14)C1]GA4 to a very small extent. Endogenous GA9 and GA24 were identified by GC-MS in methanolic nodule extracts. These results suggest that B. japonicum bacteroids would synthesize GA9 under the symbiotic conditions present in soybean root nodules.

Symbiotic hydrogenase activity in Bradyrhizobium sp. (Vigna) increases nitrogen content in Vigna unguiculata plants.

Bradyrhizobium sp. (Lupinus) and Bradyrhizobium sp. (Vigna) mutants in which hydrogenase (hup) activity was affected were constructed and analyzed. Vigna unguiculata plants inoculated with the Bradyrhizobium sp. (Vigna) hup mutant showed reduced nitrogenase activity and also a significant decrease in nitrogen content, suggesting a relevant contribution of hydrogenase activity to plant yield.

Molecular and functional characterization of the Azorhizobium caulinodans ORS571 hydrogenase gene cluster.

In this work, we report the cloning and sequencing of the Azorhizobium caulinodans ORS571 hydrogenase gene cluster. Sequence analysis revealed the presence of 20 open reading frames hupTUVhypFhupSLCDFGHJK hypABhupRhypCDEhupE. The physical and genetic organization of A. caulinodans ORS571 hydrogenase system suggests a close relatedness to that of Rhodobacter capsulatus. In contrast to the latter species, a gene homologous to Rhizobium leguminosarum hupE was identified downstream of the hyp operon. A hupSL mutation drastically reduced the high levels of hydrogenase activity induced by the A. caulinodans ORS571 wild-type strain in symbiosis with Sesbania rostrata plants. However, no significant effects on dry weight and nitrogen content of S. rostrata plants inoculated with the hupSL mutant were observed in plant growth experiments.

Paraheliotropism can protect water-stressed bean (Phaseolus vulgaris L.) plants against photoinhibition.

In order to estimate the importance of leaf movements on photosynthesis in well-watered and water-stressed field grown bean cultivars (Arroz Tuscola (AT), Orfeo INIA (OI), Bayos Titan (BT), and Hallados Dorado (HD)), CO2 assimilation, leaf temperature, and capacity for the maximum quantum yield recovery, measured as Fv/Fm, were assessed. Leaf water potential was lower in water-stressed compared to control plants throughout the day. Water status determined a decrease in the CO2 assimilation and stomatal conductance as light intensity and temperature increased up to maximal intensities at midday. Both parameters were lower in stressed compared to control plants. Even though high light intensity and water-stress induced stomatal closure is regarded as a photoinhibitory condition, the recovery of variable to maximal fluorescence (Fv/Fm) after 30min of darkness was nearly constant in both water regimes. In fact, higher values were observed in OI and AT when under stress. Photochemical and non-photochemical fluorescence quenching resulted in minor changes during the day and were similar between watered and stressed plants. It is concluded that paraheliotropism, present in the four bean cultivars, efficiently protects stressed plants from photoinhibition in the field and helps maintain leaf temperatures far below the ambient temperatures, however, it may also be responsible for low CO2 assimilation rates in watered plants.

Diversity and evolution of hydrogenase systems in rhizobia.

Uptake hydrogenases allow rhizobia to recycle the hydrogen generated in the nitrogen fixation process within the legume nodule. Hydrogenase (hup) systems in Bradyrhizobium japonicum and Rhizobium leguminosarum bv. viciae show highly conserved sequence and gene organization, but important differences exist in regulation and in the presence of specific genes. We have undertaken the characterization of hup gene clusters from Bradyrhizobium sp. (Lupinus), Bradyrhizobium sp. (Vigna), and Rhizobium tropici and Azorhizobium caulinodans strains with the aim of defining the extent of diversity in hup gene composition and regulation in endosymbiotic bacteria. Genomic DNA hybridizations using hupS, hupE, hupUV, hypB, and hoxA probes showed a diversity of intraspecific hup profiles within Bradyrhizobium sp. (Lupinus) and Bradyrhizobium sp. (Vigna) strains and homogeneous intraspecific patterns within R. tropici and A. caulinodans strains. The analysis also revealed differences regarding the possession of hydrogenase regulatory genes. Phylogenetic analyses using partial sequences of hupS and hupL clustered R. leguminosarum and R. tropici hup sequences together with those from B. japonicum and Bradyrhizobium sp. (Lupinus) strains, suggesting a common origin. In contrast, Bradyrhizobium sp. (Vigna) hup sequences diverged from the rest of rhizobial sequences, which might indicate that those organisms have evolved independently and possibly have acquired the sequences by horizontal transfer from an unidentified source.