Table 1.
Summary of infectivity, genetic stability, accumulation, and pathogenicity of 10 potato spindle tuber viroid (PSTVd) mutants in tomato plant in the first and the second passages.
| PSTVd Construct | Nucleotide Mutated | Northern-Blot Assay | Genetic Stability (4 wpi) | Systemic Accumulation | Pathogenicity | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| 42 | 43 | 64 | 310 | 312 | 1st Passage | 2nd Passage | ||||
| PSTVd-I | C | U | - | A | - | + | N.T. *1 | stable (13/13) | fast | severe |
| PSTVd-D | U | C | U | C | UU | + | N.T. *1 | stable (10/10) | slow | mild |
| I-C42U | U | U | - | A | - | + | stable (11/11) | stable (11/11) | fast | mild |
| I-U43C | C | C | - | A | - | + | revert (2/13) | revert (10/10) | (fast) *2 | (severe) *2 |
| I-64U | C | U | U | A | - | + | stable (14/14) | stable (15/15) | fast | mild |
| I-A310C | C | U | - | C | - | + | stable (13/13) | stable (11/11) | fast | severe |
| I-312UU | C | U | - | A | UU | + | unstable (UU > U; 10/12) | unstable (UU > U; 12/12) | (fast) *2 | (severe) *2 |
| D-U42C | C | C | U | C | UU | + | covariation (C43U; 10/11) | covariation (C43U; 12/12) | (slow) *2 | (mild) *2 |
| D-C43U | U | U | U | C | UU | + | stable (12/12) | stable (11/11) | slow | mild |
| D-64Δ | U | C | - | C | UU | + | covariation (310CΔ; 5/12) | covariation (310CΔ; 10/10) | (slow) *2 | (mild) *2 |
| D-C310A | U | C | U | A | UU | + | covariation (312UΔ; 5/10) | covariation (312UΔ; 10/10) | (slow) *2 | (mild) *2 |
| D-312UUΔ | U | C | U | C | - | + | stable (12/12) | stable (10/10) | slow | mild |
Nucleotides with blue background indicate PSTVd-I-type and those with green background indicate PSTVd-D-type. Numbers in parentheses indicate the number of cDNA clones which maintained stably or reverted to wild type or produced co-variation(s) per total sequence analyzed. *1. N.T. means not tested. *2. Since these mutants did not replicate stably, systemic accumulation and pathogenicity do not indicate the attributes of the original mutant itself.