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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.
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.
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.
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
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
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)
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.
