Pantoja A.,Subarctic Agricultural Research Unit |
Kuhl J.C.,U.S. Department of Agriculture |
Kuhl J.C.,University of Idaho
Plant Genetic Resources: Characterisation and Utilisation | Year: 2010
Rhubarb includes approximately 60 species in the genus Rheum. It has been utilized for thousands of years for medicinal purposes, but only recently identified for its culinary use. In the mid 1700s, edible petioles were discovered on seedlings from rhubarb species. Hundreds of cultivars have since been identified for a wide range of uses from tarts to wine. Unfortunately, propagation by seed and irregular naming has resulted in a plethora of similarly named cultivars and multitude of phenotypes. Fifteen morphological characters were evaluated to differentiate rhubarb cultivars in the USDA, ARS Rheum collection in Palmer, Alaska. Two years of morphological data, focusing on horticultural characteristics indicated variation between the years. To improve cultivar resolution, the results suggest using 1 year's data instead of combining data from different years. The mean ̊Brix observed was 3.8, with a range from 2.2 to 6.1. Flesh colour and basal skin colour were poorly correlated (R 2=0.462); overall skin colour was more red at the base than in the middle of the petiole. Rhubarb character categories, in particular petiole number and petiole base thickness, need to be modified to better anticipate the range of expected values, and thereby contribute improved reproducibility and reliability to separate cultivars based on morphological characters. © 2009 NIAB.
Ranft R.D.,University of Alaska Fairbanks |
Seefeldt S.S.,Subarctic Agricultural Research Unit |
Zhang M.,University of Alaska Fairbanks |
Barnes D.L.,University of Alaska Fairbanks
Weed Technology | Year: 2010
The use of triclopyr for the removal of woody and broad-leaf vegetation in right-of-ways and agricultural settings has been proposed for Alaska. Triclopyr concentrations in soil after application are of concern because residual herbicide may affect growth of subsequent vegetation. In order to measure triclopyr residues in soil and determine the amount of herbicide taken up by the plant, soil bioassays were developed. Four agricultural species, turnip, lettuce, mustard, and radish, were tested to determine sensitivity to triclopyr in a 1-wk bioassay. The sensitivity (I50) of turnip, lettuce, mustard, and radish was 0.33 ± 0.05 kg ai ha-1, 0.78 ± 0.11 kg ai ha-1, 0.78 ± 0.07 kg ai ha-1, and 0.85 ± 0.10 kg ai ha-1 (mean ± SE), respectively. Mustard was the most consistent crop in the bioassay with a midrange response to triclopyr and lowest standard deviation for germination as compared to the other species. Thus, it was used in a bioassay to determine triclopyr concentrations in a field trial. The bioassay of mustard closely matched residual amounts of triclopyr in a field trial determined by chemical extraction. Estimates of residual triclopyr concentrations using the bioassay method were sometimes less than the triclopyr concentration determined using a chemical extraction. These differences in concentrations were most evident after spring thaw when the chemical extraction determined there was enough triclopyr in the soil to reduce mustard growth over 60%, yet the bioassay measured only a 10 reduction. The chemical extraction method may have identified nonphototoxic metabolites of triclopyr to be the herbicidal triclopyr acid. These methods, when analyzed together with a doseresponse curve, offer a more complete picture of triclopyr residues and the potential for carryover injury to other plant species. © 2010 Weed Science Society of America.
Fielding D.J.,Subarctic Agricultural Research Unit
Journal of Orthoptera Research | Year: 2011
Female grasshoppers can affect the fitness of their offspring through their selection of oviposition sites. Successful embryological development depends on suitable temperature and moisture levels, factors which may vary greatly on a fine scale in natural environments where grasshoppers occur. Knowledge of parameters defining acceptable oviposition sites can provide guidelines for habitat manipulations that reduce the availability of such sites. This paper compares oviposition-site selection in two species of grasshopper from Alaska, Melanoplus borealis and M. sanguinipes, and a population of M. sanguinipes from Idaho. Laboratory experiments did not detect any differences in preferred substrate temperature among the groups of grasshoppers. In field cages containing a choice of different ground covers (bare ground, single clump of grass or turf), M. sanguinipes from Idaho were less selective in terms of the distribution of egg pods among the different cover types, whereas both M. borealis and M. sanguinipes from Alaska deposited the fewest egg pods under the turf. Results suggest that differences in oviposition behavior between the grasshoppers from Idaho and those from Alaska may stem more from differences in the above-ground physical structure of the vegetation, than from differences in responses to below-ground temperature.
Wu T.H.,Subarctic Agricultural Research Unit |
Bechtel P.J.,Subarctic Agricultural Research Unit
Food Chemistry | Year: 2012
There is increasing evidence that low molecular weight water soluble compounds of marine protein are important for fish performance, thus identifying and quantifying them to incorporate in feeds are needed. A simple analytical method using hydrophilic interaction liquid chromatography coupled with mass spectrometry was developed to screen for low molecular weight water soluble compounds in enzyme treated and untreated Alaskan pollock (Theragra chalcogramma) stickwater (SW) generated from processing fish meal with pollock byproduct. Sample preparation was quick and involved centrifugation with ultrafiltration membrane (cut off <3000 g/mol) of reconstituted freeze dried samples for direct analysis on mass spectrum (MS). Full MS scan (50-2000 g/mol) in dual ion mode (atmospheric pressure chemical and electrospray ionisation) resulted in the identification of 5 abundant compounds (creatine, creatinine, inosine, trimethylamine and trimethylamine oxide (TMAO)); quantification was performed with selective ion monitoring based on calibration standards. The major low molecular weight compound detected in untreated SW was TMAO at 25.2 ± 2.08 mg/g dry weight (dw) and in enzyme-treated SW was creatine at 10.5 ± 0.47 mg/g dw. © 2011 Elsevier Ltd. All rights reserved.