Heritability of Coffea canephora yield estimated from several mating designs

Eleven mating designs, 6 top-crosses and 5 North Carolina II, were used to estimate narrow sense, broad sense and within-cross heritability of Coffea canephora yield in Côte d'Ivoire. The objective was to predict achievable genetic gains according to different breeding strategies. Narrow sense, broad sense, family and within-cross heritabilities were 0.32, 0.43, 0.83 and 0.22, on average respectively. The percentage of additivity was high (81% on average). A degree of variation was nevertheless observed for estimates over trials. This was found to be mainly due to parent sampling in each trial. By theoretical computation, the minimum number of parents required to obtain optimum precision was found to be around 30. Predicted genetic gains for yield through clonal selection at a selection level of 1% ranged from 7 to 28% over the best hybrid in each trial, suggesting thus clones still interesting for breeders. The consequences for coffee breeding are discussed.     

Potential of gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) in flavor research

Gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) is an emerging technique offering a straightforward access to a resolving power up to 7000. This paper deals with the use of GC-oaTOFMS to identify the flavor components of a complex seafood flavor extract and to quantify furanones formed in model Maillard reactions. A seafood extract was selected as a representative example for complex food flavors and was previously analyzed using GC-quadrupole MS, leaving several molecules unidentified. GC-oaTOFMS analysis was focused on these unknowns to evaluate its potential in flavor research, particularly for determining exact masses. N-Methyldithiodimethylamine, 6-methyl-5-hepten-2-one, and tetrahydro-2,4-dimethyl-4H-pyrrolo[2,1-d]-1,3,5-dithiazine were successfully identified on the basis of the precise mass determination of their molecular ions and their major fragments. A second set of experiments was performed to test the capabilities of the GC-oaTOFMS for quantification. Calibration curves were found to be linear over a dynamic range of 10(3) for the quantification of furanones. The quantitative data obtained using GC-oaTOFMS confirmed earlier results that the formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone was favored in the xylose/glycine model reaction and 2(or 5)-ethyl-4-hydroxy-5(or 2)-methyl-3(2H)-furanone in the xylose/alanine model reaction. It was concluded that GC-oaTOFMS may become a powerful analytical tool for the flavor chemist for both identification and quantification purposes, the latter in particular when combined with stable isotope dilution assay.     

Formation of odorants in Maillard model systems based on l-proline as affected by pH

Formation of the odorants acetic acid, 4-hydroxy-2,5-dimethyl-3-(2H)-furanone (HDMF), 6-acetyl-1,2,3,4-tetrahydropyridine (ATHP), and 2-acetyl-1-pyrroline (AP) was monitored by isotope dilution assays at pH 6, 7, and 8 in Maillard model reactions containing glucose and proline (Glc/Pro) or the corresponding Amadori compound fructosyl-proline (Fru-Pro). In general, higher yields were obtained at pH 7 and 8. Acetic acid was the major odorant with up to 40 mg/mmol precursor followed by HDMF (up to 0.25 mg/mmol), the formation of which was favored in the Fru-Pro reaction systems. On the contrary, ATHP (up to 50 microg/mmol) and AP (up to 5 microg/mmol) were more abundant in Glc/Pro. However, the sensory relevance of the two N-heterocycles was more pronounced on the basis of odor activity values, confirming their contribution to the overall roasty note of the reaction samples. It was also found that formation and decomposition of Fru-Pro were faster at pH 7 as compared to pH 6, explaining in part the preferred formation of the four odorants studied under neutral and slightly alkaline conditions. After 4 h of reaction at pH 7 in the presence of proline, about one-fourth of the glucose was consumed leading to acetic acid with a transformation yield of almost 40 mol %.     

In-depth mechanistic study on the formation of acrylamide and other vinylogous compounds by the maillard reaction

The formation of acrylamide was studied in low-moisture Maillard model systems (180 degrees C, 5 min) based on asparagine, reducing sugars, Maillard intermediates, and sugar degradation products. We show evidence that certain glycoconjugates play a major role in acrylamide formation. The N-glycosyl of asparagine generated about 2.4 mmol/mol acrylamide, compared to 0.1-0.2 mmol/mol obtained with alpha-dicarbonyls and the Amadori compound of asparagine. 3-Hydroxypropanamide, the Strecker alcohol of asparagine, generated only low amounts of acrylamide ( approximately 0.23 mmol/mol), while hydroxyacetone increased the acrylamide yields to more than 4 mmol/mol, indicating that alpha-hydroxy carbonyls are much more efficient than alpha-dicarbonyls in converting asparagine into acrylamide. The experimental results are consistent with the reaction mechanism based on (i) a Strecker type degradation of the Schiff base leading to azomethine ylides, followed by (ii) a beta-elimination reaction of the decarboxylated Amadori compound to afford acrylamide. The beta-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in beta-position to the nitrogen atom. The beta-elimination step in the amino acid moiety was demonstrated by reacting under low moisture conditions decarboxylated model Amadori compounds obtained by synthesis. The corresponding vinylogous compounds were only generated if a beta-proton was available, for example, styrene from the decarboxylated Amadori compound of phenylalanine. Therefore, it is suggested that this thermal pathway may be common to other amino acids, resulting under certain conditions in their respective vinylogous reaction products.     

Quantitative trait loci associated with drought tolerance in the model legume Medicago truncatula

Water shortage and heterogeneity in precipitation constitute the essential limiting factors for agricultural production in the Mediterranean basin. To understand the complex inheritance of tolerance to drought stress in Medicago truncatula, quantitative trait loci (QTLs) analysis was performed using a set of recombinant inbred lines (RILs) derived from a cross between the susceptible line Jemalong A17 and the tolerant line F83005.5. We conducted two experiments where the RILs and parental lines were grown in 0 mM and 75 mM of mannitol (D-) in tubes and in control and 33% of the field capacity (FC) in pots. In both experiments, line and line by water treatment interaction were significant. QTLs analysis showed that several putative genomic regions are involved in the variation of measured traits under the two water treatments in tubes and pots. A total of 21 QTLs on 8 linkage groups were detected for the measured traits in both experiments, 11 of them were in tubes conditions. Eight of these 11 QTLs were identified in control treatment and three in mannitol. While the number of QTLs identified in tubes under control conditions was more than under mannitol conditions, the highest number of QTLs was detected in water-stressed conditions in pots. The percentage of phenotypic variance explained by a single QTL (R ²) ranges from 11.7 to 26.3% in tubes and from 11.2 to 18.4% in pots depending on the trait, with 6 QTLs in each condition explaining <15% of the phenotypic variance. The number of common QTLs under two water treatments was one for length of stems (LS), number of internodes (NIN) and aerial dry weight (ADW) in tubes, and zero for NIN and one for LS and leaf area (LA) in pots. However, a few overlapping QTLs were found in tubes and pots on linkage groups 5 and 7 for LS and NIN.     

Assessing ecological equivalence in biodiversity offset schemes: Key issues and solutions

Habitat loss through development is one of the major causes of biodiversity loss. The increasingly common legal requirement to first avoid, then reduce and, if necessary, offset impacts of plans and projects on biodiversity has however not always been appropriately enforced. The blame lies mainly in bad governance such as patchy monitoring or poorly defined liabilities. Biodiversity offsets also suffer from the lack of formal methods for designing and sizing offset requirements. We address this gap by reviewing different tools, methods and guidelines that have been developed in different regulatory contexts. We then formulate a typology of approaches that variously combine these methods and guidelines. We discuss how these relate to the objectives of offset policies and the components of biodiversity and ecosystems to which they apply. Together, these perspectives should contribute to improving existing methods (e.g. by incorporating time-related issues) and our typology should support the development of offset policies.     

Fluids from aging ocean crust that support microbial life

Little is known about the potential for life in the vast, low-temperature (<100 degrees C) reservoir of fluids within mid-ocean ridge flank and ocean basin crust. Recently, an overpressured 300-meter-deep borehole was fitted with an experimental seal (CORK) delivering crustal fluids to the sea floor for discrete and large-volume sampling and characterization. Results demonstrate that the 65 degrees C fluids from 3.5-million-year-old ocean crust support microbial growth. Ribosomal RNA gene sequence data indicate the presence of diverse Bacteria and Archaea, including gene clones of varying degrees of relatedness to known nitrate reducers (with ammonia production), thermophilic sulfate reducers, and thermophilic fermentative heterotrophs, all consistent with fluid chemistry.