TABLE 5.
Results of WF and HF soils tested for infectious ToMV by elution and bait plant methods
| Soil type and collection datea | Eluate bioassayb | Mean A405 ± SD (n)c of:
|
No. of TEM+/no. of DAS-ELISA+ extractsd | |
|---|---|---|---|---|
| Noninfected extracts | Infected extracts | |||
| WF mineral | ||||
| 6/94 | − | 0.20 ± 0.02 (6) | — | |
| 8/94 | − | 0.20 ± 0.02 (6) | — | |
| 2/95 | − | 0.19 ± 0.01 (6) | — | |
| 4/95 | − | 0.21 ± 0.02 (6) | — | |
| 9/95 | − | 0.20 ± 0.02 (5) | — | |
| 12/95 | − | 0.22 ± 0.02 (4) | 0.31 ± 0.06 (1) | 0/1 |
| WF organic | ||||
| 6/94 | − | 0.24 ± 0.02 (6) | 0.32 ± 0.03 (2) | 1/2 |
| 8/94 | − | — | 0.38 ± 0.07 (6) | 4/6 |
| 4/95 | − | 0.21 ± 0.03 (6) | — | |
| 9/95 | − | 0.20 ± 0.01 (5) | — | |
| 12/95 | − | 0.21 ± 0.02 (2) | — | |
| HF | ||||
| 2/95 | + | 0.22 ± 0.02 (4) | 0.37 ± 0 (2) | 1/2 |
| 9/95 | − | 0.20 ± 0.03 (5) | 0.39 ± 0.01 (1) | 0/1 |
Month/year.
C. quinoa plants were inoculated with concentrated soil eluates and monitored for the development of local lesions.
A bait plant root extract was considered positive for ToMV if the mean A405, as determined by DAS-ELISA, of the two sample wells was greater than the mean absorbance (plus three standard deviations) of roots of C. quinoa grown in Promix (A405 = 0.22 ± 0.01 [mean ± standard deviation]). For comparison, the A405 values of dilutions of purified ToMV were 1.7, 0.33, 0.30, and 0.21 for 100, 10, 5, and 1 ng/ml, respectively. —, no extracts.
Root extracts that tested positive for ToMV by DAS-ELISA also were examined for tobamovirus-like particles by TEM.