Inoculum sources and Preservation in Soils of Phytophthora parasitica from Cherry Tomato in Continental Crop Areas in Southeast Spain

Inoculum sources and Preservation in Soils of Phytophthora parasitica from Cherry Tomato in Continental Crop Areas in Southeast Spain

Residual effect of synthetic Zn chelates on the availability of this metal in different soils under waterlogged conditions.

Adding Zn improves crop growth, increases seed yield and also positively affects nutritional quality. After Zn fertilization, there is normally a period of several years in which residual effects provide an adequate supply of Zn to successive crops. Immediately after the application of Zn sources water-soluble Zn slowly but continually decreases. Various factors, including time and moisture conditions, affect the aging process and modify the solubility of the metal in soil and therefore its availability. In previous experiments, we studied the residual effect of synthetic chelates, obtained that the amounts of potentially available Zn decreased in the second cropping year due to aging processes. The present study was undertaken to verify variations in the residual effects of applying four different synthetic Zn sources

Endosymbiotic bacteria nodulating a new endemic lupine Lupinus mariae-josephi from alkaline soils in Eastern Spain represent a new lineage within the Bradyrhizobium genus

Lupinus mariae-josephi is a recently described endemic Lupinus species from a small area in Eastern Spain where it thrives in soils with active lime and high pH. The L. mariae-josephi root symbionts were shown to be very slow-growing bacteria with different phenotypic and symbiotic characteristics from those of Bradyrhizobium strains nodulating other Lupinus. Their phylogenetic status was examined by multilocus sequence analyses of four housekeeping genes (16S rRNA, glnII, recA, and atpD) and showed the existence of a distinct evolutionary lineage for L. mariae-josephi that also included Bradyrhizobium jicamae. Within this lineage, the tested isolates clustered in three different sub-groups that might correspond to novel sister Bradyrhizobium species. These core gene analyses consistently showed that all the endosymbiotic bacteria isolated from other Lupinus species of the Iberian Peninsula were related to strains of the B. canariense or B. japonicum lineages and were separate from the L. mariae-josephi isolates. Phylogenetic analysis based on nodC symbiotic gene sequences showed that L. mariae-josephi bacteria also constituted a new symbiotic lineage distant from those previously defined in the genus Bradyrhizobium. In contrast, the nodC genes of isolates from other Lupinus spp. from the Iberian Peninsula were again clearly related to the B. canariense and B. japonicum bv. genistearum lineages. Speciation of L. mariae-josephi bradyrhizobia may result from the colonization of a singular habitat by their unique legume host.

Lupinus mariae-josphi, a new lupin endemic of soils with active lime and high pH in South Eastern Spain, is nodulated by a new bacterial lineage within Bradyrhizobium genus

Lupinus mariae-josephi is a recently described species (Pascual, 2004) able to grow in soils with high pH and active lime content in the Valencia province (Spain). L. mariae-josephi endosymbionts are extremely slowgrowing bacteria with genetic and symbiotic characteristics that differentiate them from Bradyrhizobium strains nodulating Lupinus spp. native of the Iberian Peninsula and adapted to grow in acid soils. Cross-inoculation experiments revealed that all the endosymbiotic isolates from L. mariae-josephi tested are legume-host selective and are unable to nodulate species such as L. angustifolius, and L. luteus. In contrast, Bradyrhizobium strains from Lupinus spp. tested were able to nodulate L. mariae-josephi, although the nodules fixed nitrogen inefficiently. Phylogenetic analysis was performed with housekeeping genes (rrn, glnII, recA, atpD) and nodulation gene nodC. Housekeeping gene phylogeny revealed that L. mariae-josephi rhizobia form a strongly supported monophyletic group within Bradyrhizobium genus. This cluster also includes B. jicamae and certain strains of B. elkanii. Contrarily, isolates from other Lupinus spp. native of the Iberian Peninsula were grouped mainly within B. canariense and two B. japonicum lineages. Phylogenetic analysis of L. mariae-josephi isolates based on the nodC symbiotic gene defined a solid clade close to isolates from Algerian Retama spp. and to fast-growing rhizobia.

Percolation in soils at Different Bulk Densities: Porosity, Connectivity and Grey Threshold.

To improve percolation modelling on soils the geometrical properties of the pore space must be understood; this includes porosity, particle and pore size distribution and connectivity of the pores. A study was conducted with a soil at different bulk densities based on 3D grey images acquired by X-ray computed tomography. The objective was to analyze the effect in percolation of aspects of pore network geometry and discuss the influence of the grey threshold applied to the images. A model based on random walk algorithms was applied to the images, combining five bulk densities with up to six threshold values per density. This allowed for a dynamical perspective of soil structure in relation to water transport through the inclusion of percolation speed in the analyses. To evaluate separately connectivity and isolate the effect of the grey threshold, a critical value of 35% of porosity was selected for every density. This value was the smallest at which total-percolation walks appeared for the all images of the same porosity and may represent a situation of percolation comparable among bulks densities. This criterion avoided an arbitrary decision in grey thresholds. Besides, a random matrix simulation at 35% of porosity with real images was used to test the existence of pore connectivity as a consequence of a non-random soil structure.

Trace Elements Distribution in Red Soils under Semiarid Mediterranean Environment

This study states the potential trace elements (TE’s) content of red soils located at the centre region of Spain, characterized by low rainfall and slight acidity over prolonged weathering periods. For this purpose, three soil profiles from a catena were described, sampled and analyzed. The most notable characteristics are the low organic matter content and the predominantly acidic pH. Illite and kaolinite are the predominant clay minerals. The fertility of the soils is sufficient to provide most of the nutrients required, with very suitable potassium levels. The geochemical characters of this soil are: only few elements remain almost invariable across the profiles and over time, however the majority of them were directly linked with the clay content. These soils are characterized by relatively low levels of some trace elements such as Sr (64.35 mg?kg–1), Ba (303.67 mg?kg–1) and Sc (13.14 mg?kg–1); high levels of other trace elements such as V (103.92 mg?kg–1), Cr (79.9 mg?kg–1), Cu (15.18 mg?kg–1), Hf (10.26 mg?kg–1), Ni (38 mg?kg–1) and Zr (337 mg?kg–1); while the levels for rare earth elements (REE’s) such as La (48.36 mg?kg–1), Ce (95.07 mg?kg–1), Th (13.33 mg?kg–1) and Nd (42.65 mg?kg–1) are significantly high. The distribution of mayor and trace elements was directly re- lated to weathering processes, parent material and anthropogenic activities.