Swedish University of Agricultural Sciences

About: Swedish University of Agricultural Sciences is a education organization based out in Uppsala, Sweden. It is known for research contribution in the topics: Population & Soil water. The organization has 13510 authors who have published 35241 publications receiving 1414458 citations. The organization is also known as: Sveriges Lantbruksuniversitet & SLU.

Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora diseases

Abstract: An analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 37 research groups in 23 European countries between 1972 and 2013. Forty-nine Phytophthora taxa were recorded in 670 nurseries (91.5%); within these nurseries, 1614 of 1992 nursery stands (81.0%) were infested, although most affected plants appeared healthy. In forest and landscape plantings, 56 Phytophthora taxa were recovered from 1667 of 2525 tested sites (66.0%). Affected plants frequently showed symptoms such as crown thinning, chlorosis and dieback caused by extensive fine root losses and/or collar rot. Many well-known highly damaging host-Phytophthora combinations were frequently detected but 297 and 407 new Phytophthora-host associations were also observed in nurseries and plantings, respectively. On average, 1.3 Phytophthora species/taxa per infested nursery stand and planting site were isolated. At least 47 of the 68 Phytophthora species/taxa detected in nurseries and plantings were exotic species several of which are considered well established in both nurseries and plantings in Europe. Seven known Phytophthora species/taxa were found for the first time in Europe, while 10 taxa had not been previously recorded from nurseries or plantings; in addition, 5 taxa were first detections on woody plant species. Seven Phytophthora taxa were previously unknown to science. The reasons for these failures of plant biosecurity in Europe, implications for forest and semi-natural ecosystems and possible ways to improve biosecurity are discussed.

Differential expression of two related, low-temperature-induced genes in Arabidopsis thaliana (L.) Heynh.

Abstract: Plant cold acclimation is correlated to expression of low-temperature-induced (lti) genes. By using a previously characterized lti cDNA clone as a probe we isolated a genomic fragment that carried two closely located lti genes of Arabidopsis thaliana. The genes were structurally related with the coding regions interrupted by three similarly located short introns and were transcribed in the same direction. The nucleotide sequences of the two genes, lti78 and lti65, predict novel hydrophilic polypeptides with molecular weights of 77856 and 64510, respectively, lti78 corresponding to the cDNA probe. Of the 710 amino acids of LTI78 and 600 amino acids of LTI65, 346 amino acids were identical between the polypeptides, which suggests that the genes may have a common origin.

Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

Abstract: Conceptual models suggest that stability of or- ganic carbon (OC) in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo- mineral complexes, and location within the soil profile. Den- sity fractionation is a useful tool to study the relevance of OC stabilization in aggregates and in association with min- erals, but it has rarely been applied to full soil profiles. We aim to determine factors shaping the depth profiles of phys- ically unprotected and mineral associated OC and test their relevance for OC stability across a range of European soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sam- pled to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions - fLF, occluded light fractions - oLF, heavy fractions - HF) were analysed for OC, total nitrogen (TN), 13 C, and 1 14 C. Bulk samples were also incubated to determine CO2 evolution per g OC in the samples (specific mineralization rates) as an in- dicator for OC stability. Depth profiles of OC in the light fraction (LF-OC) matched those of roots for undisturbed grassland and forest sites, suggesting that roots are shaping the depth distribution of LF-OC. Organic C in the HF declined less with soil depth than LF-OC and roots, especially at grassland sites. The de- crease in 1 14 C (increase in age) of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the 1 14 C profiles. The LF at three sites were rather depleted in 14 C, indi- cating the presence of fossil material such as coal and lig- nite, probably inherited from the parent material. At the other sites, modern 1 14 C signatures and positive correlations be- tween specific mineralization rates and fLF-OC indicate the fLF is a potentially available energy and nutrient source for subsurface microorganisms throughout the profile. Declining specific mineralization rates with soil depth confirm greater stability of OC in subsoils across sites. The overall impor- tance of OC stabilization by binding to minerals was demon- strated by declining specific mineralization rates with in- creasing contributions of HF-OC to bulk soil OC, and the low 1 14 C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. While quanti- tatively less important than OC in the HF, consistent older ages of oLF-OC than fLF-OC suggest that occlusion of LF- OC in aggregates also contributes to OC stability in subsoils. Overall, our results indicate that association with minerals is the most important factor in stabilization of OC in soils, irre- spective of vegetation, soil type, and land use.