Field Evaluation of Cotton Expressing Mpp51Aa2 as a Management Tool for Cotton Fleahoppers, Pseudatomoscelis seriatus (Reuter)

Abstract

The cotton fleahopper (Pseudatomoscelis seriatus Reuter) is considered a highly economically damaging pest of cotton (Gossypium hirsutum L.) in Texas and Oklahoma. Current control methods rely heavily on the use of foliar-applied chemical insecticides, but considering the cost of insecticides and the critical timeliness of applications, chemical control methods are often not optimized to reduce potential yield losses from this pest. The Bacillus thuringiensis (Bt) Mpp51Aa2 (formerly Cry51Aa2.834_16) protein has proven effective against thrips and plant bugs with piercing and sucking feeding behaviors, but the impact of this toxin on cotton fleahoppers has not been investigated. To evaluate the Mpp51Aa2 trait effectiveness towards the cotton fleahopper, field trials were conducted in 2019, 2020, and 2021, comparing a cotton cultivar containing the Mpp51Aa2 trait to a non-traited isoline cultivar under insecticide-treated and untreated conditions. Populations of cotton fleahopper nymphs and adults were estimated weekly by visually inspecting cotton terminals. Square retention was also assessed during the first week of bloom to provide some insight on how the Bt trait may influence yield. While cotton fleahopper population differences between the traited and non-traited plants were not consistently noted during the pre-bloom squaring period, there was a consistent increase in square retention in cotton expressing Mpp51Aa2 relative to non-traited cotton. Additionally, cotton expressing Mpp51Aa2 offered similar square protection relative to non-traited cotton treated with insecticides for the cotton fleahopper. These findings indicate that the Mpp51Aa2 protein should provide benefits of delayed nymphal growth, population suppression, and increased square retention.

Choice and No-Choice Feeding Assays of Cotton Fleahoppers (Pseudatomoscelis seriatus) on Cotton Expressing the Mpp51Aa2 Protein

“…Adult and nymph feeding damage on the ThryvOn cotton appeared to be negligible in the no-choice assay. These findings align with the observations by Arthur et al [35], where significantly higher square retention was found in ThryvOn cotton compared to a gene-lacking cultivar among diverse cotton fleahopper population densities across multiple years in the field. These results suggest that, even under forced conditions, cotton fleahoppers did not cause significant damage to ThryvOn cultivars.…”

“…This could potentially be explained by the high levels of infestation used in this study. As shown by Arthur et al [35], cotton expressing the Mpp51Aa2 protein suffered a significant square loss when exposed to high populations of cotton fleahoppers. Previous research has consistently concluded that ThryvOn cotton can deter the feeding of various insect pests of cotton, including tobacco thrips (Frankliniella fusca Hinds), western flower thrips (Frankliniella occidentalis Pergande), onion thrips (Thrips tabaci Lindeman), tarnished plant bugs, western tarnished plant bugs, and cotton fleahoppers [18,36,37].…”

“…Confirmation of the activity of ThryvOn cotton in a controlled environment increases the confidence that the implementation of ThryvOn cotton into an insect pest management strategy for cotton fleahoppers could offer valuable square protection by deterring insect feeding. As concluded from other studies, the feeding deterrence of ThryvOn cotton in a field setting could reduce the necessity for foliar insecticides, offering flexibility in the timing of applications for optimal efficacy [21,23,35]. Moreover, the increased square retention observed in ThryvOn cotton, even under high infestation levels, could alleviate much of the time and labor required to optimally manage cotton fleahoppers in cotton production.…”

“…The prevalence of large nymphs corresponds to higher damage levels and reduced yields across varying infestation levels [18]. Arthur et al [35] also reported a 2.6:1 ratio of small to large cotton fleahopper nymphs in ThryvOn cotton compared to a 1.1:1 ratio in a gene-lacking cultivar, along with increased fruit retention in the ThryvOn cultivar. Our results suggest a potential rationale for the differences in square retention percentages observed between the ThryvOn and gene-lacking cultivars: large nymphs tend to cause greater damage to cotton compared to adults.…”

Draft Genome Sequence of Bacillus thuringiensis INTA 103-23 Reveals Its Insecticidal Properties: Insights from the Genomic Sequence

“…Renowned for its remarkable protein synthesis machinery, B. thuringiensis synthesizes a diverse array of insecticidal proteins, including Cry, Cyt, Vip, Vpa/Vpb, and Sip, each exhibiting a high specificity against various insect orders [2]. The integration of genes encoding these insecticidal proteins into crops, known as Bt crops, imparts targeted resistance against insect pests [3].…”