Acid‐extractable potassium in agricultural soils: Source minerals assessed by differential and quantitative X‐ray diffraction

Different extraction methods are used world‐wide in routine soil analysis to estimate long‐term potassium (K) reserves for plants. In Sweden, K extracted with 2 M HCl at 100°C (K_HCl) is frequently used, although with limited understanding of the phases extracted. In the present study, we quantified the effects of this extraction on soil minerals in particle size fractions ranging from clay to sand, and estimated their relative contribution to K_HCl. The study included three Swedish long‐term agricultural field experiments with texture ranging from loamy sand to silty clay, as well as mineral specimens of K feldspar. Total weight loss of particle size fractions was determined, and quantitative and differential X‐ray powder diffraction (QXRD, DXRD), applied on solids before and after extraction, was used to quantify the dissolution of individual mineral phases. QXRD and DXRD included spray‐drying of samples, addition of an internal standard and full pattern fitting, where a combination of mineral‐standard XRD traces was matched with the experimental one. Our results show that K_HCl was primarily associated with clay minerals concentrated in the two finest fractions (2–20 and < 2 μm). Highly expandable and mixed‐layer phyllosilicates were quantitatively the most important minerals dissolved. The K was released from micaceous layers in mixed‐layer phyllosilicates with a vermiculitic character. Whether di‐ or trioctahedral, a shared property of the dissolved phases was that they were rich in Fe. In the loamy sand, the coarser fractions (20–2000 μm), where feldspars were prominent, accounted for 35% of K_HCl. According to DXRD, there was no significant decrease in K feldspars in any of the samples, and K_HCl data for the feldspar specimens suggest that clay minerals contributed at least 70% of K_HCl also in the loamy sand. Our study provides insights about the soil minerals that contribute to the long‐term K delivery capacity of soils and an explanation for the prior observation that K_HCl is a dynamic fraction that can be affected by management.     

Identification,mapping and evolutionary course of wheat lipoxygenase-1 genes located on the A genome

Durum wheat (Triticum turgidum) is the cereal of preference for semolina and pasta production. Bright yellow color, which is desirable for pasta making, depends on the amount of carotenoid pigments present in the grain. Lipoxygenases (LPXs) account for most of the carotenoid degradation activity. Although B genome Lpx genes have been extensively described, little information about the A genome has been reported. Here, we demonstrate that the Lpx-A1 locus is represented by a single gene in the diploid Triticum urartu, the tetraploid T. turgidum and the hexaploid Triticum aestivum wheats in contrast to the multiple copies reported in the B genome. The Lpx-A1_like pseudogene previously identified in T. turgidum genome A was also identified in the T. aestivum cv Chinese Spring wheat, whereas T. urartu possesses a complete copy, suggesting that pseudogenization occurred after the formation of the tetraploid and then passes to the hexaploid wheat. The nucleotide sequence of T. urartu Lpx is more closely related to genome B Lpx-1 than to Lpx genes of genome A from T. turgidum and T. aestivum, probably due to the deletions and insertions that occur. Thus, the present paper extends our knowledge of lipoxygenase gene organization and evolution in the wheat A genome.     

Eosinophilic keratoconjunctivitis in two rabbits

The purpose of this case report is to describe the clinical course and cytologic findings, treatment, and outcome of eosinophilic keratoconjunctivitis in two rabbits. Ophthalmic examination revealed ocular discharge, dacryocystitis, blepharitis, conjunctivitis, white conjunctival and corneal plaques, corneal vascularization, and stromal infiltration with different degrees of severity in each case. In case 2 there was also ulcerative disease of the cornea. Computerized tomography scan of the head, corneal biopsy for histopathologic examination with additional Luna and Giemsa stain were performed in case 2 and conjunctival as well as corneal specimens were obtained for bacteriologic culture and cytologic examination in case 1. Based on test results, a diagnosis of eosinophilic keratoconjunctivitis was made in case 2 and a tentative diagnosis of eosinophilic keratoconjunctivitis was made in case 1. Response to treatment with a topical steroid and topical cyclosporin was supportive of the diagnosis in both cases and shared many similarities with the response to treatment previously described in cats. Eosinophilic keratitis should be considered as part of a differential diagnosis list in rabbits with a history of keratitis.     

Genetic conservation of potentially immunogenic proteins among Brazilian isolates of Babesia bovis

Bovine babesiosis caused by Babesia bovis remains an important constraint for the development of cattle industries worldwide. Effective control can be achieved by vaccination with live attenuated phenotypes of the parasite. However, these vaccines have a number of drawbacks, which justifies the search for better, safer vaccines. In recent years, a number of parasite proteins with immunogenic potential have been discovered. However, there is little information on the genetic conservation of these proteins among different parasite isolates, which hinders their assessment as immunogens. The aim of the present study was to evaluate the conservation of the genes ama-1, acs-1, rap-1, trap, p0 and msa2c among five Brazilian isolates of B. bovis. Through polymerase chain reaction, genetic sequencing and bioinformatics analysis of the genes, a high degree of conservation (98-100%) was found among Brazilian isolates of B. bovis and the T2Bo isolate. Thus, these genes are worth considering as viable candidates to be included in a recombinant cocktail vaccine for cattle babesiosis caused by B. bovis.