Andean potato cultivars (Solanum tuberosum L.) as a source of antioxidant and mineral micronutrients

Potato tubers were evaluated as a source of antioxidants and minerals for the human diet. A genetically diverse sample of Solanum tuberosum L. cultivars native to the Andes of South America was obtained from a collection of nearly 1000 genotypes using microsatellite markers. This size-manageable collection of 74 landraces, representing at best the genetic diversity among potato germplasm, was analyzed for iron, zinc, calcium, total phenolic, total carotenoid, and total vitamin C contents. The hydrophilic antioxidant capacity of each genotype was also measured using the oxygen radical absorbance capacity (ORAC) assay. The iron content ranged from 29.87 to 157.96 microg g-1 of dry weight (DW), the zinc content from 12.6 to 28.83 microg g-1 of DW, and the calcium content from 271.09 to 1092.93 microg g-1 of DW. Total phenolic content varied between 1.12 and 12.37 mg of gallic acid equiv g-1 of DW, total carotenoid content between 2.83 and 36.21 microg g-1 of DW, and total vitamin C content between 217.70 and 689.47 microg g-1 of DW. The range of hydrophilic ORAC values was 28.25-250.67 micromol of Trolox equiv g-1 of DW. The hydrophilic antioxidant capacity and the total phenolic content were highly and positively correlated (r = 0.91). A strong relationship between iron and calcium contents was also found (r = 0.67). Principal component analysis on the studied nutritional contents of the core collection revealed that most potato genotypes were balanced in terms of antioxidant and mineral contents, but some of them could be distinguished by their high level in distinct micronutrients. Correlations between the micronutrient contents observed in the sample and the genetic distances assessed by microsatellites were weakly significant. However, this study demonstrated the wide variability of health-promoting micronutrient levels within the native potato germplasm as well as the significant contribution that distinct potato tubers may impart to the intake in dietary antioxidants, zinc, and iron.     

Antioxidant profiling of native Andean potato tubers (Solanum tuberosum L.) reveals cultivars with high levels of beta-carotene, alpha-tocopherol, chlorogenic acid, and petanin

The antioxidant profile of 23 native Andean potato cultivars has been investigated from a human nutrition perspective. The main carotenoid and tocopherol compounds were studied using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) and a fluorescence detector, respectively, whereas polyphenols (including anthocyanins in colored tubers) were identified by means of both HPLC-mass spectrometry and HPLC-DAD. Antioxidant profiling revealed significant genotypic variations as well as cultivars of particular interest from a nutritional point of view. Concentrations of the health-promoting carotenoids, lutein and zeaxanthin, ranged from 1.12 to 17.69 microg g(-1) of dry weight (DW) and from 0 to 17.7 microg g(-1) of DW, with cultivars 704353 and 702472 showing the highest levels in lutein and zeaxanthin, respectively. Whereas beta-carotene is rarely reported in potato tubers, remarkable levels of this dietary provitamin A carotenoid were detected in 16 native varieties, ranging from 0.42 to 2.19 microg g(-1) of DW. The amounts of alpha-tocopherol found in Andean potato tubers, extending from 2.73 to 20.80 microg g(-1) of DW, were clearly above the quantities generally reported for commercial varieties. Chlorogenic acid and its isomers dominated the polyphenolic profile of each cultivar. Dark purple-fleshed tubers from the cultivar 704429 contained exceptionally high levels of total anthocyanins (16.33 mg g(-1) of DW). The main anthocyanin was identified as petanin (petunidin-3-p-coumaroyl-rutinoside-5-glucoside). The results suggest that Andean potato cultivars should be exploited in screening and breeding programs for the development of potato varieties with enhanced health and nutritional benefits.     

Step-wise analysis of precipitation and river chemistry trends in Atlantic Canada

Monotonic trends in hydrogen (H⁺), sulfate (SO₄ ^–2)and nitrate (NO₃ ^–) were calculated using non-parametric techniques at four Canadian Air and Precipitation Monitoring Network (CAPMoN) sites and six nearby river systems in Atlantic Canada for the period 1983–1991. Over the whole interval, there were increasing nitrate concentrations and deposition trends at three of the four monitoring sites and no trends in SO₄ ^–2 or H⁺ concentrations and deposition. We found that SO₄ ^–2 concentrations increased at three of our six river sites, NO₃ ^– increased at one site and H⁺ decreased at one site. River exports showed no trends in the entire study interval. The series were also analyzed in five year time windows, incremented by six months, to see if changes in trend presence or direction would occur, compared to trend analysis over the entire interval. We show that while trends in river chemistry do not contradict deposition patterns, the changes that occurred were not necessarily in step. We also found that the trends which we measured were the result of short-term changes as opposed to long-term continuous monotonic trends. The time lag between precipitation and chemistry trend changes seemed longer in basins dominated by softwoods than by hardwoods.     

A new fertilization strategy in declining forests

In central Europe and to some degree in North America, the so called “new type” forest damages occur over large areas. Various studies indicate the declines are more or less frequently associated with nutritional disturbances that have developed within rather short time periods. The most common disorder is a Mg deficiency that produces specific discoloration symptoms such as tip-yellowing in Norway spruce. But also K deficiencies and other disturbances exist in coniferous as well as in deciduous forests. Good correlations between the site specific substrate chemistry and the actual nutritional status of the trees and stands were found. To explain the sudden and widespread development of the forest declines adverse anthropogenic influences such as increased N and H⁺ deposition, land use and forestry mismanagement as well as natural stresses are discussed. The hypothesized causal mechanisms are multiple, but include generally soil degradation processes associated with losses of alkaline nutrient ions from the rooted solum. Recent and previous fertilization (and liming) experiments have shown that a fast and sustained revitalization and restabilization of declining forest ecosystems marked by nutrient deficiencies can be achieved. This was demonstrated by chemical and histological foliar analyses and the visible improvement of the trees. Soil analyses also revealed a positive change of the chemical soil status when site and stand specific fertilizer applications were utilized in the appropriate amounts. However, under certain site and stand conditions risks and limitations exist that have to be evaluated when fertilization practices are discussed.To overcome or minimize these influences the treatments. must be adapted to the site, and stand specific fertilization needs as indicated by soil and foliar analysis, humus form, hydrologic parameter and atmospheric deposition rates.     

The decreasing radial wood stiffness pattern of some tropical trees growing in the primary forest is reversed and increases when they are grown in a plantation

Background   

This study examines the radial trend in wood stiffness of tropical rainforest trees. The objective was to determine if the type of growing environment (exposed plantation or dense primary forest) would have an effect on this radial trend.     

Intrapopulation Recombination for 15N-Determined Dinitrogen Fixation Ability in Common Bean

The quantity of N₂ fixed in common bean (Phaseolus vulgaris L.) is a quantitatively inherited trait that shows sufficient genetic variability for improvement through breeding, but there is little information on gain from selection for ¹⁵N-determined N₂ fixation ability. The objective was to determine whether intrapopulation recombination and selection could be used to improve N₂ fixation. Four agronomically acceptable lines were selected, based on their acetylene reduction-determined N₂ fixation ability, from an inbred backcross (IB) line population created from a cross between the high N₂-fixing donor parent ‘Puebla 152’ and a commercial, low N₂-fixing recurrent parent ‘Sanilac’. These four IB lines were intercrossed, advanced to the F₃, and the six resulting F₃ populations with 25 F₃ families per population were evaluated for N₂ fixation in a low-N field using ¹⁵N-depleted (NH₄)₂SO₄. The six F₃ population means differed significantly and were superior to ‘Sanilac’ for N₂ fixation ability and yield, indicating significant improvement over ‘Sanilac’. Four F₃ population means were similar to ‘Puebla 152’, indicating selection advance towards high N₂ fixation while retaining favorable agronomic characteristics. Fifty percent of the F₃ families were superior to ‘Sanilac’ for N₂ fixation and one family exceeded ‘Puebla 152’, indicating that intrapopulation recombination produced improvement of ¹⁵N-determined N₂ fixation.