Interspecific hybridization of Fragaria moschata with two diploid species, F. nubicola and F. viridis

The crosses Fragaria moschata × F. nubicola, F. moschata × F. viridis, and their reciprocal combinations were done to create tetraploids for eventual introgression into octoploid cultivars of Fragaria × ananassa via the synthetic octoploid system. The combination F. nubicola × F. moschata averaged 3.3 healthy plants/pollination, which was 2.3 times higher than the next best combination, F. moschata × F. viridis. Fragaria viridis × F. moschata crosses averaged only 0.1 healthy plants/pollination and no plants were obtained from F. moschata × F. nubicola hybridizations. The success of the F. nubicola × F. moschata crosses in this study indicated that embryo/endosperm ratios were not as important a factor in producing hybrids with F. moschata × diploids species, as previously suggested.Although 90% of pollinated flowers set fruit with an average of 19 seeds/pollination only 15% of the seeds contained healthy, white embryos and only 38% of these developed into healthy seedlings. The remaining 62% of embryos lacked pigment, had short hypocotyls or arrested development after slight expansion out of the seed coat. Only 39% of the crosses resulted in viable progenies. After one year, 27% of these hybrids bloomed and 71% of the blooming hybrids were tetraploids. All six diploid and six of the seven hexaploid accessions were successfully incorporated into 89 hybrids.     

Influence of wildfire severity on riparian plant community heterogeneity in an Idaho,USA wilderness

Despite the increasing recognition of riparian zones as important ecotones that link terrestrial and aquatic ecosystems and of fire as a critical natural disturbance, much remains unknown regarding the influence of fire on stream-riparian ecosystems. To further this understanding, we evaluated the effects of mixed severity wildfire on riparian plant community structure and composition in headwater streams of the Big Creek Watershed of the Frank Church ‘River of No Return’ Wilderness of central Idaho. Five years after a large stand-replacing fire, we conducted riparian vegetation surveys at sixteen reaches across a range of burn types. Non-metric Multidimensional Scaling (NMS) and Multi-Response Permutation Procedure (MRPP) analyses showed an overall shift in community composition and structure between vegetation at unburned and severely burned reaches. Although total plant cover was significantly less at severely burned areas, recovery of the deciduous understory was apparent. Severely burned reaches were characterized by a marked increase in cheatgrass (Bromus tectorum). Reaches that were exposed to low-severity fire were indistinguishable from unburned reaches relative to vegetation community composition and structure, pointing to a possible disturbance threshold that may need to be crossed in order to alter riparian plant communities.     

Critical Loads of Acidity to Protect and Restore Acid-Sensitive Streams in Virginia and West Virginia

The purpose of the research described here is to apply a new approach for generating aquatic critical load (CL) and exceedance calculations for an important acid-sensitive region of the eastern USA. A widespread problem in regional aquatic acidification CL modeling for US ecosystems has been the lack of site-specific weathering data needed to derive accurate model CL estimates. A modified version of the steady-state water chemistry CL model was applied here to estimate CL and exceedances for streams throughout acid-sensitive portions of Virginia and West Virginia. A novel approach for estimating weathering across the regional landscape was applied, based on weathering estimates extracted from a well-tested, process-based watershed model of drainage water acid?Cbase chemistry and features of the landscape that are available as regional spatial data coverages. This process allowed extrapolation of site-specific weathering data from 92 stream watersheds to the regional context in three ecoregions for supporting CL calculations. Calculated CL values were frequently low, especially in the Blue Ridge ecoregion where one-third of the stream length had CL?<?50?meq/m²/year to maintain stream ANC at 50???eq/L under steady-state conditions. About half or more of the stream length in the study region was in exceedance of the CL for long-term aquatic resource protection under assumed nitrogen saturation at steady state. Land managers and air quality policy makers will need this information to better understand responses to air pollution emissions reductions and to develop ecoregion-specific air pollution targets.     

Ascorbic acid determination in processed potatoes

A method to determine ascorbic acid at any stage of potato processing was developed. Potato samples are frozen in dry ice, lyophilized and analyzed using a modified spectrophotometric method. This method is simple, accurate, inexpensive and has a detection limit of 1.2 mg ascorbic acid/100 g dry weight potatoes.