Inheritance of fiber quality and lint yield in a chemically mutated population of cotton

The narrow germplasm base of the upland cotton (Gossypium hirsutum L.), grown on the Texas high plains historically, has limited improvement of fiber quality. Chemical mutagenesis and subsequent selection have helped the development of lines with improved fiber quality in cultivars adapted to this region. This study was conducted to determine the inheritance of improvements in fiber quality. M₃ lines with divergent fiber properties of micronaire, length, and strength were selected from a population of Paymaster HS 200 treated with 3% v/v ethyl methanesulfonate (EMS) for two hours. The 115 selected lines of M₄ and M₅ generation were evaluated for fiber quality and lint yield. Regression of the M₄ and M₅ on the M₃ generation, as well as the M₅ on the M₄ was used to generate narrow sense heritability coefficients. Significant variations were observed between the mutant lines in all generations except for lint yield in the M₅ (1997). The highest heritability estimates were found in fiber length (h ²= 0.29** to 0.46**). Micronaire and strength showed intermediate heritability estimates of h ²= 0.14 to 0.19, while lint yield had a very low heritability estimate of h ²= 0.03. Fiber length and strength were correlated (r= 0.58** to 0.46**) in all the three generations. The mutants identified in these studies have the potential to improve fiber quality of upland cotton without introducing alien genes that may reduce adaptation to short growing season production regions.     

Atmospheric CO2 enrichment and nutrient additions to planted soil increase mineralisation of soil organic matter, but do not alter microbial utilisation of plant- and soil C-sources

Plants link atmospheric and soil carbon pools through CO₂ fixation, carbon translocation, respiration and rhizodeposition. Within soil, microbial communities both mediate carbon-sequestration and return to the atmosphere through respiration. The balance of microbial use of plant-derived and soil organic matter (SOM) carbon sources and the influence of plant-derived inputs on microbial activity are key determinants of soil carbon-balance, but are difficult to quantify. In this study we applied continuous ¹³C-labelling to soil-grown Lolium perenne, imposing atmospheric CO₂ concentrations and nutrient additions as experimental treatments. The relative use of plant- and SOM-carbon by microbial communities was quantified by compound-specific ¹³C-analysis of phospholipid fatty acids (PLFAs). An isotopic mass-balance approach was applied to partition the substrate sources to soil respiration (i.e. plant- and SOM-derived), allowing direct quantification of SOM-mineralisation. Increased CO₂ concentration and nutrient amendment each increased plant growth and rhizodeposition, but did not greatly alter microbial substrate use in soil. However, the increased root growth and rhizosphere volume with elevated CO₂ and nutrient amendment resulted in increased rates of SOM-mineralisation per experimental unit. As rhizosphere microbial communities utilise both plant- and SOM C-sources, the results demonstrate that plant-induced priming of SOM-mineralisation can be driven by factors increasing plant growth. That the balance of microbial C-use was not affected on a specific basis may suggest that the treatments did not affect soil C-balance in this study.     

New insights on 3-mercaptohexanol (3MH) biogenesis in Sauvignon Blanc wines: Cys-3MH and (E)-hexen-2-al are not the major precursors

The molar conversion yield of Cys-3MH into 3MH, during alcoholic fermentation, was traced using a deuterated isotope of the precursor added to different Sauvignon Blanc musts. This yield is close to that found in synthetic media supplemented with synthetic Cys-3MH, that is, below 1%. Yet, this represents only 3-7% of the total 3MH production in wine. This clearly shows that Cys-3MH is a precursor of 3MH, but not the main one in the different musts tested. The contribution of ( E)-hex-2-enal, which has been suggested as another potential precursor of 3MH, was discarded as well, as shown using also a deuterated analogue. The third suggested precursor of 3MH is a glutathionyl-3MH (G-3MH), which upon proteolytic degradation could release Cys-3MH. The knockout of the OPT1 gene, which encodes the major glutathione transporter, reduces 3MH accumulation by a 2-fold factor in grape must as compared to the wild type strain. Consequently, it is deduced that major 3MH precursor(s) are transported into yeast via Opt1p, which is in favor of G-3MH being a 3MH precursor. This work opens the search for the major natural precursor(s) of 3MH in Sauvignon Blanc must.     

Kinetics of leaf temperature fluctuation affect isoprene emission from red oak (Quercus rubra) leaves

Because the rate of isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature-dependent, we investigated natural fluctuations in leaf temperature and effects of rapid temperature change on isoprene emission of red oak (Quercus rubra L.) leaves at the top of the canopy at Harvard Forest. Throughout the day, leaves often reached temperatures as much as 15 degrees C above air temperature. The highest temperatures were reached for only a few seconds at a time. We compared isoprene emission rates measured when leaf temperature was changed rapidly with those measured when temperature was changed slowly. In all cases, isoprene emission rate increased with increasing leaf temperature up to about 32 degrees C and then decreased with higher temperatures. The temperature at which isoprene emission rates began to decrease depended on how quickly measurements were made. Isoprene emission rates peaked at 32.5 degrees C when measured hourly, whereas rates peaked at 39 degrees C when measurements were made every four minutes. This behavior reflected the rapid increase in isoprene emission rate that occurred immediately after an increase in leaf temperature, and the subsequent decrease in isoprene emission rate when leaf temperature was held steady for longer than 20 minutes. We concluded that the observed temperature response of isoprene emission rate is a function of measurement protocol. Omitting this parameter from isoprene emission models will not affect simulated isoprene emission rates at mild temperatures, but can increase isoprene emission rates at high temperatures.     

Grassland community composition drives small-scale spatial patterns in soil properties and processes

The presence and activity of individual plants can affect soil resource availability and microbial processes, and can influence the spatial scale over which soil properties vary. While soils have been found to differ under plants of differing growth form (i.e. grasses vs. trees), few studies have focused on small-scale soil differences under comparably-sized species. Here we investigate how two types of C-3 grasses influence patterns in soil properties and processes at scales of less than one meter in a California grassland. To understand how native perennial grasses differ from invasive annual grasses in their effects on soils, we used cross-semivariogram analysis to quantify the degree and scale of spatial heterogeneity in soil properties and processes in experimentally-seeded grasslands. We then used mapping techniques to correlate spatial patterns of soil properties and processes with the cover of annual and perennial grasses aboveground. We found that many soil properties and processes belowground were spatially-correlated with the aboveground presence of annuals or perennials. Soil moisture became more heterogeneous with increasing amounts of perennial cover, suggesting that perennial bunchgrass individuals take up more water and produce zones of resource depletion in comparison with soils directly under annual grasses. The association of belowground resources and activity with the two types of grass suggests that the historical shift from perennial to annual dominance in California grasslands led to changes in the small-scale spatial structure of soil properties and processes in these systems. These changes may alter ecosystem function and could potentially perpetuate invasive annual grass dominance.     

Fish‐processing wastes as an alternative diet for culturing the minute rotifer Proales similis de Beauchamp

We evaluated the suitability of fish waste diet (FWD) for culturing the minute rotifer Proales similis through the observation of their population growth and particle size selective feeding. A total of five treatments either with Nannochloropsis oculata or FWD (0.75 and 0.50 g/L) or the combination of N. oculata and FWD were set up in triplicates. P. similis were cultured in diluted natural seawater (8 g/L salinity) and 26 ± 1°C with the diet treatments being applied randomly. We daily monitored the rotifer density, the number of bacteria and the water quality in all the cultures. The population density of P. similis increased exponentially in all treatments, while the mean growth in FWD 0.75 g/L was significantly higher (p < .05) than that in the control. Addition of N. oculata to FWD resulted to lowered P. similis population growth. Bacterial colony count was high in FWD and introduction of P. similis to the diet decreased their density. The estimated bacteria ingestion rates were generally in the range of 6.03 × 10²–1.24 × 10⁴ bacteria/rotifer/hr and there was a positive linear relationship between bacterivory and rotifer population growth. We also observed a shift in the particle size distribution with a reduction in the frequency and concentration of small‐sized particles (<2.5 μm) at day 6. These results accentuate the potential of fish‐processing waste as diet for culturing P. similis which feeds on bacteria and small particles (≤2.5 μm) that are by‐products of degradation of this diet.     

Determination of the conjugated linoleic acids in cow's milk fat by Fourier transform Raman spectroscopy

The collective term "conjugated linoleic acid" or "CLA" generally refers to a mixture of conjugated positional and geometric isomers of linoleic (cis-9,cis-12-octodecadienoic) acid. In nature, these isomers are mainly formed in the rumen by biohydrogenation of polyunsaturated fatty acids. This study concerns a first trial of CLA determination in cow's milk fat by Raman spectroscopy. The spectra of pure cis-9-oleic, cis-9,cis-12-linoleic, cis-9,trans-11-linoleic, and trans-10,cis-12-linoleic acids have been examined in comparison with the spectra of selected milk-fat samples containing between 0 and 3% of CLA. The trial of CLA determination by Raman spectroscopy on cow milk fat has reached its objective with the two following results. First, the examination of the Raman spectra allows to identify three specific Raman signals of the chemical bonds associated to the cis,trans conjugated C=C in the rumenic and trans-10,cis-12-octodecadienoic acids at 1652, 1438, and 3006 cm(-1). Second, the calibration of Raman spectrometer for the CLA determination has indicated that these three specific signals suit very well for the accurate and reliable measurement of CLA concentration in milk fat. To our knowledge, the present study is the first successful attempt to determine the CLA content of milk fat by a spectrophotometric method.     

Impact of lipid physical state on the oxidation of methyl linolenate in oil-in-water emulsions

The purpose of this research was to examine the influence of the physical state of lipids on iron-promoted oxidation of methyl linolenate in octadecane oil-in-water emulsions. Octadecane and methyl linolenate oil-in-water emulsions were prepared that contained droplets having the octadecane as either liquid or solid. The physical state of the octadecane was confirmed by a differential scanning calorimeter (DSC). The effect of the physical state of the lipid on oxidation rates was determined as a function of iron concentration (80 and 160 microM), pH (3.0 or 7.0), emulsifier type, and cooling rate. Oxidation of methyl linolenate was determined by lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS). Emulsions containing solid octadecane had higher rates of lipid hydroperoxide and TBARS formation than those containing liquid octadecane. The rate at which the emulsions were cooled had no influence on oxidation rates. Oxidation rates in both emulsions increased with increasing iron concentration and decreasing pH. Oxidation rates were lowest in emulsions with cationic droplet membranes (dodecyl trimethylammonium bromide-stabilized), presumably due to the repulsion of iron from the oxidizable methyl linolenate in the emulsion droplet core. These results suggest that upon crystallization of octadecane, the liquid methyl linolenate migrated to the emulsion droplet surface, where it was more prone to oxidation because it was in closer contact with the iron ions in the aqueous phase.