Table 1.
Characteristics of sites sampled for total rhizosphere DNA
| Sample | Geographic coordinates | Total no. of phzF clones | Phz+ population density (log CFU g root−1 [fresh wt])a | Phz+ plant colonization frequency | Agroclimate zoneb | Mean annual precipitation (mm)c |
|---|---|---|---|---|---|---|
| S1.1 | 46°47′49″N, 118°32′57″W | 51 | 5.4 ± 0.6 | 1.0 | Grain/fallow | 259 |
| S1.2 | 46°46′53″N, 118°21′28″W | 54 | 5.6 ± 1.0 | 0.7 | Grain/fallow | 297 |
| S1.3 | 46°46′50″N, 117°56′58″W | 52 | 5.3 ± 0.8 | 0.8 | Annual crop; dry | 371 |
| S1.4 | 46°48′40″N, 117°40′22″W | 55 | 6.3 ± 0.6 | 0.6 | Grain/fallow | 430 |
| S2.1 | 47°16′33″N, 118°41′34″W | 52 | 5.4 ± 1.3 | 0.6 | Grain/fallow | 273 |
| S2.2 | 47°4′20″N, 118°38′7″W | 52 | 5.7 ± 0.9 | 0.6 | Grain/fallow | 265 |
| S2.3 | 46°56′26″N, 118°34′26″W | 46 | 5.3 ± 0.8 | 0.8 | Grain/fallow | 258 |
| S2.5 | 46°50′9″N, 117°22′18″W | 44 | 4.8 ± 0.5 | 0.2 | Annual crop; fallow-transition | 512 |
| S2.8 | 46°45′20″N, 117°6′41″W | 48 | 5.0 ± 0.6 | 0.3 | Annual crop; wet-cool | 581 |
a
At each location, 16 plants were randomly sampled and root suspensions were used to determine population density and plant colonization by the terminal endpoint dilution assay (1, 8). Values are means ± standard deviations.
b
Agroclimatic zones defined by Douglas et al. (22).
c
Mean annual precipitation data for 30 years (1971–2000) from the PRISM Climate Group (www.prism.oregonstate.edu/).