Mapping QTLs for aluminum tolerance in maize

Aluminum toxicity is one of the major constraints for plant development in acid soils, limiting food production in many countries. Cultivars genetically adapted to acid soils may offer an environmental compatible solution, providing a sustainable agriculture system. The aim of this work was to identify genomic regions associated with Al tolerance in maize, and to quantify the genetic effects on the phenotypic variation. A population of 168F_3:4 families derived from a cross between two contrasting maize inbred lines for Al tolerance was evaluated using the NSRL and RSRL parameters in nutrient solution containing toxic level of aluminum. Variance analyses indicated that the NSRL was the most reliable phenotypicindex to measure Al tolerance in the population, being used for further QTL mapping analysis. RFLP and SSR markers were selected for bulked segregant analysis, and additional SSR markers, flanking the polymorphisms of interest, were chosen in order to saturate the putative target regions. Seven linkage groups were constructed using 17 RFLP and 34 SSR markers. Five QTLs were mapped on chromosomes 2, 6 and 8, explaining 60% of the phenotypic variation. QTL₄ and marker umc043 were located on chromosomes 8and 5, close to genes encoding for enzymes involved in the organic acids synthesis pathways, a widely proposed mechanism for Al tolerance in plants. QTL₂ was mapped in the same region as Alm2,also associated with Al tolerance in maize. In addition, dominant and additive effects were important in the control of this trait in maize. This revised version was published online in July 2006 with corrections to the Cover Date.     

Laboratory study of the effects of two nitrification inhibitors on greenhouse gas emissions from a slurry-treated arable soil: impact of diurnal temperature cycle

An automated laboratory soil incubation system enabled the effects on gaseous emissions from a soil to be quantified accurately, when amended with slurry plus a nitrification inhibitor: dicyandiamide (DCD), or 3,4-dimethylpyrazole phosphate (DMPP). Nitrification inhibitors applied with slurry under simulated Portuguese conditions were very efficient in reducing N₂O emission, and did not increase CH₄ emissions significantly, when the soil was predominantly aerobic. The inhibitors were also indirectly effective in reducing N₂O emissions due to denitrification during a subsequent anaerobic phase. All gaseous emissions followed strong diurnal patterns that were positively correlated with soil temperature and obeyed a Q₁₀=2 relationship. The widespread use of DCD and DMPP inhibitors with slurry applied to Portuguese soils could have the potential to reduce N₂O emissions from this source by ten- to 20-fold.     

Cadophora luteo-olivacea isolated from apple (Malus domestica) fruit with post-harvest side rot symptoms in northern Italy

European Journal of Plant Pathology - Recently, Cadophora luteo-olivacea has been reported as a post-harvest pathogen of side rot of apple (Malus domestica) in Latvia, and of pear (Pyrus communis)...     

Humoral and cellular immune responses in dogs with inapparent natural Leishmania infantum infection

Molecular analysis, serology and immunophenotyping for T lymphocytes and their subsets, B lymphocytes and monocytes were performed on dogs naturally infected with Leishmania infantum. Animals were categorised as asymptomatic dogs I (AD-I), with negative serology and positive molecular results, and asymptomatic dogs II (AD-II), with positive serology and positive molecular results, and these were compared to symptomatic dogs (SD) and control dogs (CD). AD-I exhibited immunophenotypic features similar to those of CD, including isotype profiles and concentrations of monocytes. Similar biomarkers were found in AD-II and SD, such as, higher levels of immunoglobulins IgG, IgG2, IgM and IgA and higher concentrations of eosinophils. High frequencies of T lymphocytes and CD4(+) T cells were observed in both AD-I and AD-II compared to SD, whereas CD8(+) T cells were higher only in AD-II compared with SD. Analysis of B lymphocytes revealed an increased frequency of this cell type only in AD-II animals compared with SD. Asymptomatic dogs appear to have a dichotomous infection spectrum that can influence the humoral and cellular immunological status during canine visceral leishmaniasis.     

Volatile compounds in samples of cork and also produced by selected fungi

The production of volatile compounds by microbial communities of cork samples taken during the cork manufacturing process was investigated. The majority of volatiles were found in samples collected at two stages: resting after the first boiling and nontreated cork disks. Volatile profiles produced by microbiota in both stages are similar. The releasable volatile compounds and 2,4,6-trichloroanisole (TCA) produced in cork-based culture medium by five isolated fungal species in pure and mixed cultures were also analyzed by gas chromatography coupled with mass spectrometry (GC-MS).The results showed that 1-octen-3-ol and esters of fatty acids (medium chain length C8-C20) were the main volatile compounds produced by either pure fungal species or their mixture. Apparently, Penicillium glabrum is the main contributor to the overall volatile composition observed in the mixed culture. The production of releasable TCA on cork cannot be attributed to any of the assayed fungal isolates.     

Lipid-stimulated somatostatin secretion in rainbow trout,Oncorhynchus mykiss

Previous work has shown that somatostatins (SS) affect teleost lipid metabolism indirectly by inhibition of insulin (INS) and directly by stimulation of hepatic lipolysis. In the present study, rainbow trout (Oncorhynchus mykiss) were used to characterize further the lipid-SS relationship by evaluating how lipid, contributes to SS secretion bothin vivo andin vitro. In vivo hyperlipidemia was induced for up to 3 h by short-term (2 min) infusion of a triacylglycerol (TG)-rich lipid emulsion (20% Intralipid^®). Plasma total lipid concentration increased 118 and 155% over control levels 1 h and 3 h, respectively, after infusion; much of this increase was due to elevated plasma fatty acids (FA), which increased 39 and 520%, respectively, over the same time-frame. The hyperlipidemic pattern was attended by a significant increase in the plasma concentration of SS. The specific effects of fatty acids were evaluated on isolated Brockmann bodies. Palmitic acid and oleic acid stimulated SS release 378 and 82%, respectively, over baseline levels. These results indicate that lipids, and in particular fatty acids, modulate SS secretion in rainbow trout.     

Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness

The cosmopolitan and increasing distribution of Cylindrospermopsis raciborskii can be attributed to its ecophysiological plasticity and tolerance to changing environmental factors in water bodies. In reservoirs in the semi-arid region of Brazil, the presence and common dominance of C. raciborskii have been described in waters that are considered hard. We investigated the response of a Brazilian C. raciborskii strain to water hardness by evaluating its growth and saxitoxin production. Based on environmental data, a concentration of 5 mM of different carbonate salts was tested. These conditions affected growth either positively (MgCO₃) or negatively (CaCO₃ and Na₂CO₃). As a control for the addition of cations, MgCl₂, CaCl₂ and NaCl were tested at 5 or 10 mM, and MgCl₂ stimulated growth, NaCl slowed but sustained growth, and CaCl₂ inhibited growth. Most of the tested treatments increased the saxitoxin (STX) cell quota after six days of exposure. After 12 days, STX production returned to concentrations similar to that of the control, indicating an adaptation to the altered water conditions. In the short term, cell exposure to most of the tested conditions favored STX production over neoSTX production. These results support the noted plasticity of C. raciborskii and highlight its potential to thrive in hard waters. Additionally, the observed relationship between saxitoxin production and water ion concentrations characteristic of the natural environments can be important for understanding toxin content variation in other harmful algae that produce STX.     

Isolation of Mycobacterium bovis from brushtail possums with non-visible lesions

AIM: To determine the prevalence of Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula) that did not have macroscopic lesions of bovine tuberculosis, and to evaluate culture of pooled tissues from multiple possums as a method for determining the M. bovis-infection status of wildlife populations in New Zealand.

METHODS: Pools of selected tissues were collected from possums from four different populations known to be infected with M. bovis. Tissue pools from individual animals, and combined pools from multiple animals, were cultured for M. bovis.

RESULTS: In the four populations investigated, the prevalence of possums with macroscopic lesions confirmed by culture to be infected with M. bovis ranged from 1 to 19 (mean 31/283; 10.9)%. The prevalence of possums with non-visible lesions that were culture positive for M. bovis in the same populations ranged from 4 to 10 (mean 24/283; 8.5)%. The mean of the log10 cfu of M. bovis of the macroscopic lesions and of the culture-positive samples that did not have visible lesions was 3.85 (SE 0.26) and 1.46 (SE 0.26) log₁₀ cfu, respectively (p<0.01). Mycobacterium bovis was cultured from pools of 30–50 animals in the four populations studied.

CONCLUSIONS: The finding of M. bovis infection in possums with non-visible lesions identified a potential deficiency of declaring possum populations free of M. bovis on the basis of absence of macroscopic lesions. The culturing of pools of selected tissues from multiple animals without visible lesions can be used to reduce laboratory costs of possum surveys without a major reduction in the ability to detect M. bovis infection.