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Your search keyword '"Kravchenko, Alexandra N."' showing total 134 results
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134 results on '"Kravchenko, Alexandra N."'

20. Barley HVA1 gene confers salt tolerance in R3 transgenic oat

Author

Oraby, Hesham F., Ransom, Callista B., Kravchenko, Alexandra N., and Sticklen, Mariam B.

Subjects
Barley -- Genetic aspects -- Research, Oats -- Genetic aspects -- Research, Genetically modified crops -- Research -- Genetic aspects, Agricultural industry, Business, Genetic aspects, Research
Abstract

A major cause of oat crop yield loss worldwide is osmotic stress due to drought and/or salinity. This study investigated the third generation of transgenic oat (A vena sativa L.) expressing barley HVA1 stress tolerance, β-glucuronidase (uidA; gus) and bar herbicide resistance genes. Transgenic plants showed normal 9:7 third generation inheritance for glufosinate ammonium herbicide resistance. Molecular and histochemical studies confirmed the presence and stable expression of all three genes. Compared with the nontransgenic control plants, transgenic R3 plants exhibited greater growth and showed a significant (P < 0.05) increase in tolerance to salt stress conditions (200 mM NaCl) for traits including number of days to heading, plant height, flag leaf area, root length, panicle length, number of spikelets/panicle, number of tillers/plant, number of kernels/panicle, 1000-kernel weight, and kernel yield/plant., ENVIRONMENTAL STRESSES such as drought and salinity represent some of the most limiting factors for agricultural productivity worldwide (Boyer, 1982; Roy and Wu, 2002). Not only do they greatly decrease [...]

Published
2005

26. Genetic analysis of standardized collections of cackling and Canada goose harvests

Author

Shorey Rainy I., Scribner, Kim T., Prince, Harold H., Kravchenko, Alexandra N., Luukkonen, David R., and Padding, Paul I.

Subjects
Canada goose -- Analysis, Canada goose -- Genetic aspects, Waterfowl management -- Research, Zoology and wildlife conservation
Abstract

A study using established methods of genetic stock identification and standardized harvest sample collections to estimate proportional contributions of cackling and Canada geese are presented. Results reveal that proportions of giant and interior Canada geese within local harvest varied significantly.

Published
2007

27. X‐ray computed tomography to predict soil N2O production via bacterial denitrification and N2O emission in contrasting bioenergy cropping systems.

Author

Kravchenko, Alexandra N., Guber, Andrey K., Quigley, Michelle Y., Koestel, John, Gandhi, Hasand, and Ostrom, Nathaniel E.

Subjects
*DENITRIFICATION, *ORGANIC compounds, *PLANT diversity, *CARBON in soils, *SOIL moisture
Abstract

While renewable biofuels can reduce negative effects of fossil fuel energy consumption, the magnitude of their benefits depends on the magnitude of N2O emissions. High variability of N2O emissions overpowers efforts to curb uncertainties in estimating N2O fluxes from biofuel systems. In this study, we explored (a) N2O production via bacterial denitrification and (b) N2O emissions from soils under several contrasting bioenergy cropping systems, with specific focus on explaining N2O variations by accounting for soil pore characteristics. Intact soil samples were collected after 9 years of implementing five biofuel systems: continuous corn with and without winter cover crop, monoculture switchgrass, poplars, and early‐successional vegetation. After incubation, N2O emissions were measured and bacterial denitrification was determined based on the site‐preference method. Soil pore characteristics were quantified using X‐ray computed microtomography. Three bioenergy systems with low plant diversity, that is, corn and switchgrass systems, had low porosities, low organic carbon contents, and large volumes of poorly aerated soil. In these systems, greater volumes of poorly aerated soil were associated with greater bacterial denitrification, which in turn was associated with greater N2O emissions (R2 = 0.52, p < 0.05). However, the two systems with high plant diversity, that is, poplars and early‐successional vegetation, over the 9 years of implementation had developed higher porosities and organic carbon contents. In these systems, volumes of poorly aerated soil were positively associated with N2O emissions without a concomitant increase in bacterial denitrification. Our results suggest that changes in soil pore architecture generated by long‐term implementation of contrasting bioenergy systems may affect the pathways of N2O production, thus, change associations between N2O emissions and other soil properties. Plant diversity appears as one of the factors determining which microscale soil characteristics will influence the amounts of N2O emitted into the atmosphere and, thus, which can be used as effective empirical predictors. Long‐term implementation of bioenergy systems with contrasting plant diversity influences microscale pore architecture, which then affects predictors of N2O production and emission. [ABSTRACT FROM AUTHOR]

Published
2018
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34. Forms and Functions of Meso and Micro-niches of Carbon within Soil Aggregates

Author

Smucker, Alvin J.M., Wang, Wei, Kravchenko, Alexandra N., and Dick, Warren A.

Subjects
Symposium Paper, complex mixtures
Abstract

Soil aggregates include sand/silt/clay, water, ion and organic matter contents combined with natural dry/wet (D/W) cycling alters both the formation and function of intra-aggregate pore continuity, connectivity, dead-end storage volumes, and tortuosity. Surface aggregates in the 0-5 cm depths of most soils experience from 34 to 57 D/W cycles that exceed differences in water contents10%. Both the rates of drying or wetting, (intensity) and the D/W range of soil water contents (severity) alter the transport of water, C and N through micro and mesofaunal habitats among multiple size domains. This report identifies micro-niche locations of accumulating soil C within soil aggregate regions that may affect nematode residence sites and migration pathways. Recent advances in X-ray microtomography enable the examination of intact pore networks within soil aggregates at resolutions as small as 4 microns. Geostatistical and multi-fractal methods provide concise characteristics of pore spatial distributions within the aggregates and are useful for comparing these alterations among soils. Aggregates subjected to multiple D/W cycles developed greater spatial correlations that parallel increases in the (13)C sorption within aggregate interiors were compared with locations of soil microbial communities. Past research indicates microbial activities within the soil aggregate matrix are spatially heterogeneous due to complex pore geometries within aggregates. Illumination of the "blackbox" interiors of soil aggregates includes a discussion of natural and anthropogenic alterations of solution flow and carbon sequestration by soil aggregates containing biophysical gradients.

Published
2010

49. Barley HVA1Gene Confers Salt Tolerance in R3 Transgenic Oat

Author

Oraby, Hesham F., Ransom, Callista B., Kravchenko, Alexandra N., and Sticklen, Mariam B.

Abstract

A major cause of oat crop yield loss worldwide is osmotic stress due to drought and/or salinity. This study investigated the third generation of transgenic oat (Avena sativaL.) expressing barley HVA1stress tolerance, β‐glucuronidase (uidA; gus) and barherbicide resistance genes. Transgenic plants showed normal 9:7 third generation inheritance for glufosinate ammonium herbicide resistance. Molecular and histochemical studies confirmed the presence and stable expression of all three genes. Compared with the nontransgenic control plants, transgenic R3 plants exhibited greater growth and showed a significant (P< 0.05) increase in tolerance to salt stress conditions (200 mMNaCl) for traits including number of days to heading, plant height, flag leaf area, root length, panicle length, number of spikelets/panicle, number of tillers/plant, number of kernels/panicle, 1000‐kernel weight, and kernel yield/plant.

Published
2005
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50. TB-infected deer are more closely related than non-infected deer

Author

Blanchong, Julie A, Scribner, Kim T, Kravchenko, Alexandra N, and Winterstein, Scott R

Abstract

Identifying mechanisms of pathogen transmission is critical to controlling disease. Social organization should influence contacts among individuals and thus the distribution and spread of disease within a population. Molecular genetic markers can be used to elucidate mechanisms of disease transmission in wildlife populations without undertaking detailed observational studies to determine probable contact rates. Estimates of genealogical relationships within a bovine tuberculosis-infected white-tailed deer (Odocoileus virginianus) population indicated that infected deer were significantly more closely related than non-infected deer suggesting that contact within family groups was a significant mechanism of disease transmission. Results demonstrate that epidemiological models should incorporate aspects of host ecology likely to affect the probability of disease transmission.

Published
2007
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