Evaluation of Cotton Fleahopper (Pseudatomoscelis seriatus (Reuter)) Feeding on Mpp51Aa2-Traited Cotton Utilizing Electrical Penetration Graph (EPG) Waveforms

Abstract

Prior to the recent implementation of the Mpp51Aa2 pesticidal protein (ThryvOn), transgenic cotton cultivars have historically offered no control of the cotton fleahopper (Pseudatomocelis seriatus (Reuter)). To evaluate the feeding behavior of cotton fleahoppers on ThryvOn cotton, electropenetrography (EPG) using a Giga-8 DC instrument was used to monitor the probing activity of fourth- and fifth-instar cotton fleahopper nymphs on both ThryvOn and non-ThryvOn cotton squares. Nymphs were individually placed on an excised cotton square for 8 h of EPG recording, after which resulting waveforms were classified as non-probing, cell rupturing, or ingestion. Although there were significantly more cell rupturing events per insect on ThryvOn (mean ± SEM, 14.8 ± 1.7) than on non-ThryvOn squares (mean ± SEM, 10.3 ± 1.6), there was no difference attributable to ThryvOn in the average number of ingestion events per insect. However, the average duration of ingestion events was significantly shorter on squares with ThryvOn (mean ± SEM, 509 ± 148 s) than on squares without (mean ± SEM, 914 ± 135 s). This suggests that cotton fleahoppers continued to probe despite their inability to sustain ingestion. These results provide conclusive evidence that the Mpp51Aa2 pesticidal protein affects the feeding behavior of cotton fleahopper nymphs.

Keywords: EPG; Gossypium hirsutum; Mpp51Aa2; Psuedatomoscelis seriatus; ThryvOn; cotton fleahopper; electrical penetration graph; electropenetrography.

Figure 1

Overview of characteristic electropenetrography waveforms associated with cotton fleahopper probing behaviors: cell rupturing events (A), ingestion events (B) and non-probing events (C). Boxed sections of the waveform are magnified in the inset boxes. Arrows indicate the initiation of a probe.

Figure 2

Mean ± SEM numbers of cell rupturing events (A) and ingestion events (B) recorded for cotton fleahopper nymphs on ThryvOn and non-ThryvOn cotton. Asterisks indicate treatments are significantly different (ANOVA, Student’s p < 0.05), ns indicates no significant differences.

Figure 3

Relationship between cell rupturing events and the number of ingestion events between ThryvOn and non-ThryvOn cotton squares. The relationship of the feeding behaviors on ThryvOn was best fit by a logistic growth regression model (I = 7.381344/(5.582 × 10^{(−0.313*CR) + 1.104)}) (R² = 0.5262), while the non-ThryvOn was a linear regression model I = (0.3208 × CR + 1.485) (R² = 0.7641).

Figure 4

Mean ± SEM duration (A) and total duration (B) of cell rupturing events exhibited by cotton fleahopper nymphs on ThryvOn and non-ThryvOn cotton. Asterisks indicate treatments are significantly different (ANOVA, Student’s p < 0.05), ns indicates no significant differences.

Figure 5

Mean ± SEM duration (A) and total duration (B) of ingestion events exhibited by cotton fleahopper nymphs on ThryvOn and non-ThryvOn cotton. Asterisks indicate treatments are significantly different (ANOVA, Student’s p < 0.05), ns indicates no significant differences.

Figure 6

Mean ± SEM percentage of sustained ingestion events exhibited by cotton fleahopper nymphs on ThryvOn and non-ThryvOn cotton. Asterisks indicate treatments are significantly different (ANOVA, Chi-square p < 0.05).

Figure 7

Mean ± SEM percentage of total duration of non-probing activity per insect exhibited by cotton fleahopper nymphs on ThryvOn and non-ThryvOn cotton. Asterisks indicate treatments are significantly different (ANOVA, Student’s p < 0.05), ns indicates no significant differences.