Table 3.
Detection of Ralstonia solanacearum using nitrocellulose membrane enzyme-linked immunosorbent assay (NCM ELISA), polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and quantitative PCR (qPCR) on field-collected potato tubers in Kenyaa
| Origin | Sample ID | NCM ELISA | Conventional PCR | IpxC LAMP (Thermocycler) | qPCR Mean Ct values 6 SD)b |
|---|---|---|---|---|---|
| Kirinyaga County | Kirinyaga-1 | + | + | + | 28.3 ± 0.1 |
| Kirinyaga-2 | + | + | + | 29.0 ± 0.4 | |
| Kirinyaga-3 | + | + | + | 27.8 ± 0.3 | |
| Kirinyaga-4 | + | + | + | 29.4 ± 0.7 | |
| Molo County | Molo-1 | − | − | − | 39.0 ± 0.2 |
| Molo-2 | + | + | + | 26.9 ± 0.1 | |
| Molo-3 | + | + | + | 30.0 ± 0.2 | |
| Molo-4 | − | + | + | 28.7 ± 0.3 | |
| Meru County | Meru-1 | + | + | + | 31.6 ± 0.4 |
| Meru-2 | − | − | − | 38.7 ± 0.3 | |
| Meru-3 | − | − | − | 38.8 ± 0.4 | |
| Meru-4 | − | + | + | 32.8 ± 0.2 | |
| Nyandarua County | Nyandarua-1 | − | − | + | 30.9 ± 0.4 |
| Nyandarua-2 | + | + | + | 28.4 ± 0.3 | |
| Nyandarua-3 | + | + | + | 28.4 ± 0.1 | |
| Nyandarua-4 | + | + | + | 31.7 ± 2.2 | |
| Nakuru County | Nakuru-1 | − | − | − | ND |
| Nakuru-2 | + | + | + | 28.1 ± 0.2 | |
| Nakuru-3 | − | − | − | 37.9 ± 1.2 | |
| Nyeri County | Nyeri-1 | + | + | + | 34.7 ± 0.4 |
| Nyeri-2 | − | + | + | 34.6 ± 0.9 | |
| Nyeri-3 | + | + | + | 33.6 ± 1.2 | |
| Nyeri-4 | + | + | + | 32.3 ± 0.4 | |
| Narok County | Narok-1 | − | + | + | 34.4 ± 1.4 |
| Narok-2 | + | + | + | 27.1 ± 0.6 | |
| Narok-3 | + | + | + | 29.1 ± 0.4 | |
| Narok-4 | + | + | + | 25.5 ± 0.5 | |
| Bomet County | Bomet-1 | + | + | + | 26.2 ± 0.6 |
| Bomet-2 | + | + | + | 25.4 ± 0.1 | |
| Bomet-3 | − | + | + | 33.6 ± 1.2 | |
| Bomet-4 | + | + | + | 24.5 ± 0.4 | |
| Koibatek County | Koibatek-1 | + | + | + | 26.6 ± 0.8 |
| Koibatek-2 | + | + | + | 26.5 ± 1.1 | |
| Koibatek-3 | − | − | + | 29.9 ± 0.1 | |
| Koibatek-4 | + | + | + | 29.5 ± 1.6 | |
| Bungoma County | Elgon-1 | + | + | + | 25.3 ± 0.3 |
| Elgon-2 | + | + | + | 25.4 ± 0.3 | |
| Elgon-3 | + | + | + | 23.1 ± 0.4 | |
| Elgon-4 | + | + | + | 24.9 ± 0.7 | |
| Uasin Gishu County | UasinGishu-1 | + | + | + | 24.2 ± 0.5 |
| UasinGishu-2 | + | + | + | 25.6 ± 0.4 | |
| UasinGishu-3 | − | + | + | 25.2 ± 0.2 | |
| UasinGishu-4 | + | + | + | 25.1 ± 0.5 | |
| Kisii County | Kisii-1 | + | + | + | 26.5 ± 0.2 |
| Kisii-2 | + | + | + | 23.9 ± 0.0 | |
| Kisii-3 | + | + | + | 23.8 ± 0.1 | |
| Kisii-4 | + | + | + | 22.9 ± 0.4 | |
| Controls | Healthy potato tubers | − | − | − | ND |
| No-template control | − | − | − | ND | |
| Positive control | + | + | + | 15.8 ± 0.1 |
Data from different detection techniques performed in three technical replications. The numbers in the sample ID (1 to 4) indicate the number of the fields tested in a region. A plus sign (+) indicates a positive test result for field potato samples tested (for NCM ELISA, purple color comparable to positive control; for conventional PCR [759/760], observed presence of amplified PCR products of 280 bp when viewed by gel electrophoresis; and for IpxC LAMP, translucent blue color). A minus sign (–) indicates a negative test result for field potato samples tested (for NCM ELISA, no color development on NCM ELISA nitrocellulose membrane; for conventional PCR [759/760], no amplified PCR product on gel; and for IpxC LAMP, translucent violet color). ND indicates not detected.
Values are mean cycle threshold (Ct) of three replicates ± standard deviation for the 47 field samples tested using qPCR.