Figure 1
Percentage of Meloidogyne javanica second-stage juveniles (J2) killed after 24-hr exposure to volatiles emitted by 20 mL of cassava wastewater. The interactions between experiments and treatments were not significant (P = 0.063), then the data were analyzed together (n = 12). ***Significant at the 0.001 probability level according to Student’s t-test when compared to negative control.
Figure 2
Chromatogram showing the eight compounds identified in the cassava wastewater volatiloma. 1. ethanol, 2. propan-2-ol, 3. propan-1-ol, 4. butan-2-ol, 5. butan-1-ol, 6. acetic acid, 7. ethyl butanoate, 8. butyric acid.
Table 1
VOCs identified in cassava wastewater by SPME–GC–MS.
| Compound | Retention Time (min) | Classes | IR. Expa | IR. Litb | Peak area (×104) | |
|---|---|---|---|---|---|---|
| (1) | Ethanol | 2.07 | Alcohol | – | – | 65.5 |
| (2) | Propan-2-ol | 2.19 | Alcohol | – | – | 23.5 |
| (3) | Propan-1-ol | 2.43 | Alcohol | – | 595 | 8.2 |
| (4) | Butan-2-ol | 2.71 | Alcohol | 601 | 598 | 53.1 |
| (5) | Butan-1-ol | 3.30 | Alcohol | 657 | 668 | 19.4 |
| (6) | Acetic acid | 3.50 | Carboxylic acid | 669 | 642 | 236.2 |
| (7) | Ethyl butanoate | 5.96 | Ester | 800 | 802 | 46.4 |
| (8) | Butyric acid | 8.91 | Carboxylic acid | 815 | 790 | 5,034.2 |
Figure 3
Dose-response curve of Meloidogyne javanica second-stage juveniles (J2) exposed to compounds with nematicidal activity. M. javanica J2 were exposed for 48 hr at 28°C to different concentrations of ethyl butanoate (A) and butyric acid (B). Dose-response curves were determined using a logistic model. Unfilled circles indicate the raw data collected in each experimental unit. The 95% confidence interval is represented by the shaded region around the curve. The interactions between experiments and treatments were not significant (P > 0.05), then the data were analyzed together.
Table 2
Dose-response curve log-logistic equation parameters for Meloidogyne javanica second-stage juveniles exposed to butyric acid and ethyl butanoate.
| Model parameter | ||||
|---|---|---|---|---|
| Compounds | bw | cx | dx | ez |
| Butyric acid | –9.74 (0.75)a P < 0.001 | Fixed | Fixed | 172.61 (1.15) P < 0.001 |
| Ethyl butanoate | –2.65 (0.22) P < 0.001 | Fixed | 92 (0.064) P < 0.001 | 301.20 (7.12) P < 0.001 |
Table 3
Concentrations (μg ∙ mL–1) that resulted in 50% of Meloidogyne javanica second-stage juveniles’ (J2) population mortality (LC50).
| Compounds | Model predicted LC50–48 hr(μg ∙ mL–1)a | |
|---|---|---|
| Butyric acid | 172.61 (170.34–174.87) | |
| Ethyl butanoate | 301.20 (257.82–344.58) |
Figure 4
Boxplot depicting the galls (A) and eggs (B) per gram of tomato root system grown in substrate infested with Meloidogyne javanica in a greenhouse with temperature ranging from 20°C to 28°C. Substrate infested with M. javanica eggs was fumigated with butyric acid or ethyl butanoate at a dose of 0.5 mL ∙ L-1 of substrate. The commercial nematicide Dazomet was used as a positive control and water as a negative control. Boxes followed by the same letter do not differ by the Tukey test at 5% probability (P < 0.05). The interactions between experiments and treatments were not significant (P = 0.485), then the data were analyzed together. Unfilled circles the observations.
Table 4
RFM of tomato plants cultivated in substrate infested with Meloidogyne javanica eggs and fumigated with butyric acid or ethyl butanoate at a dose of 0.5 mL ∙ L–1 of substrate.
| Treatments | RFM |
|---|---|
| Ethyl butanoate | 8.81 ± 1.75 b |
| Butyric acid | 7.34 ± 1.43 b |
| Dazomet | 11.03 ± 3.71 a |
| Control (water) | 7.91 ± 1.85 b |
[i] Within column, means ± standard error followed by the same letter do not differ significantly from each other by the Tukey test (P < 0.05). The interactions between experiments and treatments were not significant (P > 0.05), then the data were analyzed together. Values are means of 12 replicates per treatment.
RFM, root fresh mass.