The gram-negative bacterium Campylobacter jejuni has extensive reservoirs in livestock and the environment and is a frequent cause of gastroenteritis in humans. To date, the lack of (i) methods suitable for population genetic analysis and (ii) a universally accepted nomenclature has hindered studies of the epidemiology and population biology of this organism. Here, a multilocus sequence typing (MLST) system for this organism is described, which exploits the genetic variation present in seven housekeeping loci to determine the genetic relationships among isolates. The MLST system was established using 194 C. jejuni isolates of diverse origins, from humans, animals, and the environment. The allelic profiles, or sequence types (STs), of these isolates were deposited on the Internet (http://mlst.zoo.ox.ac.uk), forming a virtual isolate collection which could be continually expanded. These data indicated that C. jejuni is genetically diverse, with a weakly clonal population structure, and that intra- and interspecies horizontal genetic exchange was common. Of the 155 STs observed, 51 (26% of the isolate collection) were unique, with the remainder of the collection being categorized into 11 lineages or clonal complexes of related STs with between 2 and 56 members. In some cases membership in a given lineage or ST correlated with the possession of a particular Penner HS serotype. Application of this approach to further isolate collections will enable an integrated global picture of C. jejuni epidemiology to be established and will permit more detailed studies of the population genetics of this organism.

Research scale combines currently available are not designed to harvest windrowed seed crops. A pickup attachment was constructed from a commercially available unit that allows mechanized harvest of windrows with plot-scale combines. This piece of equipment was used successfully during the 1989 season to harvest a variety of seed crops.

Although many crops are commonly field dried in windrows, research has often been limited by the lack of adequate equipment for small-plot windrowing. A research scale windrowing machine was constructed that closely imitates commercial practice. The machine was used on a number of crops in 1989.

Nitrogen management programs of soft white winter wheat (Triticum aestivum L.) in semiarid regions are generally based upon soil tests of available water and residual N levels. The purpose of this work was to develop postharvest criteria for N-sufficiency and N-insufficiency based on tissue protein levels as it relates to maximum grain yield in a fallow-wheat rotation. Yield-protein relationships in grain, straw, and chaff tissues were examined in field trials from 4 harvest years on a Walla Walla silt loam (coarse-silty, mixed, mesic, Typic Haploxeroll). Grain protein content was a better postharvest indicator of N sufficiency for maximum grain yield than straw or chaff protein levels. Excessive weed growth confounded this relationship in 1 year. Using a chi-square interaction procedure, a critical level of 8.8% grain protein was determined necessary for N sufficiency in ‘Stephens’ soft white winter wheat when weed growth was not a management problem. The transition zone between N sufficient and N insufficient responses was between 8.3 and 9.1% grain protein. The amount of relative yield lost to N insufficiency was related to grain protein content. There was a 9.8% yield reduction for each grain protein percentage below 9.1. Critical protein values indicative of N insufficiency could not be determined for straw and chaff tissues. Straw and chaff protein levels greater than 2.6 and 3.5%, respectively, were exclusively associated with N sufficiency.

Published January 1983. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog

AbstractSoil moisture measurements with a neutron‐probe moisture meter provide a rapid and non‐destructive means for measuring soil water in long‐term studies. The inability of farm machinery to pass over the extended access tube limits its use in some situations. A retractable, neutronprobe access tube was designed to allow implement passage at the normal speed and tillage depth without contacting the access tube.This design has been used for soil‐moisture studies in a fallow‐crop rotation in which 6 to 10 tillage operations, including planting, have been performed over the access tubes. It has worked well with disks, sweeps, harrows, chisels, and deep‐furrow planters.

AbstractIn the Pacific Northwest, potential yield and erosion control are affected by time of stand establishment of winter cereals. The objectives of this study were: 1) to investigate the effect of soil temperature on the rate of first and 70% emergence of winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.) in the field; and, 2) develop a means of predicting the average effect of planting date on emergence at one location in eastern Oregon.Two depths of soil mulch on stubble‐ and bare‐fallowed field plots were used to investigate the effect they have on soil temperature and on rates of first and 70% emergence. The soil was a Walla Walla silt loam (mixed, mesic Typic Haploxeroll). McDermid wheat was planted at biweekly intervals from August to November 1976 and 1977. Hudson barley was planted at similar intervals in the fall of 1976. Seeds were placed in moist soil with a deep furrow drill. Average soil temperatures were 0.5‐2.0 C higher at 10 cm under the bare‐fallow than under the stubble‐fallow treatments, but tillage did not affect emergence rate.Regression equations of emergence rate and average 10‐cm soil temperature at a nearby U.S. Weather Bureau shelter were highly significant. The equations indicated that wheat required 149 and 210 degree days above a minimum of 0.7 and 0.4 C to obtain first and 70% emergence, respectively. Barley required 92 and 159 degree days above a minimum of 6.1 and 3.5 C for first and 70% emergence, respectively. A graph of 15‐year average daily 10‐cm temperature from 1 August through 30 November at Moro, Ore., was used with the equation to predict: 1) the average last date of planting to obtain emergence within a specified time period; and 2) the average length of time needed for emergence when the crops are planted on a given date. The average latest time to plant and obtain 70% emergence within 14 days is the last week of September.

AbstractTomato plants were studied to assess the potential value of ethanol accumulation in plant tissue as a measure of O2 stress resulting from short periods of soil flooding. Ethanol concentration in xylem exudate was markedly associated with air temperature, and to a lesser extent with light intensity and soil temperature under conditions of flooding. Field flooding results agreed closely with simulated environments.A small amount of ethanol was eliminated by transpiration from flooded tomato plants under environmental conditions that favored accumulation. A slightly higher amount of ethanol was excreted from the roots.Ethanol in tomato plant samples appeared to indicate the intensity of O2 deficiency during flooding by reflecting both soil O2 supply and environmental effects, and could serve as a useful indicator in relating tomato plant injury to flooded conditions.