Edison Agrosciences (United States)

UK-2A is an antifungal antibiotic produced by Streptomyces sp. 517-02. Derivatization of its picolinamide OH to form the isobutyryl acetal led to the discovery of fenpicoxamid (InatreqTM active), which is currently under development as a fungicide by Dow AgroSciences LLC. This paper documents efforts to achieve additional efficacy enhancements through semi-synthetic modification of the benzyl substituent of the UK-2A macrocycle. Of 34 analogs prepared, the most active had mitochondrial electron transport IC50 values 1.5- to 3.7-fold higher than UK-2A (IC50 0.86 nM). The cyclohexyl analog (38, IC50 1.23 nM) was the most intrinsically active derivative, and inhibited in vitro growth of Zymoseptoria tritici (EC50 2.8ppb) and Leptosphaeria nodorum (EC50 6.2ppb) more strongly than UK-2A (EC50 5.3 and 11.3ppb for Z. tritici and L. nodorum, respectively). Heterocyclic ring systems and polar linker functionalities resulted in substantial activity loss. Several analogs (20, 22, 23, 24, 36 and 38) translated Z. tritici in vitro growth inhibition activity to in planta disease control more effectively than did UK-2A, with log D being a key factor in this regard. UK-2A is amenable to further modification at the benzyl position on the macrocycle, which provides opportunities for manipulation of physical properties while retaining strong intrinsic and antifungal activity. © 2019 Society of Chemical Industry.

The front cover image of the herbicide, 2,4‐D, inside the deep binding pocket of the auxin receptor protein known as TIR1, by Roberto Busi et al., is based on the Review Weed resistance to synthetic auxin herbicides, DOI: 10.1002/ps.4823. image

RNA interference (RNAi) was discovered almost 20 years ago and has been exploited worldwide to silence genes in plants and animals. A decade later, it was found that transforming plants with an RNAi construct targeting an insect gene could protect the plant against feeding by that insect. Production of double‐stranded RNA (dsRNA) in a plant to affect the viability of a herbivorous animal is termed trans‐kingdom RNAi (TK‐RNAi). Since this pioneering work, there have been many further examples of successful TK‐RNAi, but also reports of failed attempts and unrepeatable experiments. Recently, three laboratories have shown that producing dsRNA in a plant's chloroplast, rather than in its cellular cytoplasm, is a very effective way of delivering TK‐RNAi. Our review examines this potentially game‐changing approach and compares it with other transgenic insect‐proofing schemes. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

An insecticide screening effort identified N-(4-bromophenyl)-4,6-bis(2,2,2-trifluoroethoxy)-1,3,5-triazine-2-amine as having weak potency against two lepidopteran species, Helicoverpa zea and Spodoptera exigua. A structure-activity relationship study about the trifluoroethoxy substituents and the aniline of this compound was carried out in an effort to improve insecticidal potency. Initially, a series of analogs bearing various substituents on the aniline were prepared, and the insecticidal potency was evaluated against H. zea and S. exigua in greenhouse diet feeding assays. The results showed that electron-withdrawing substituents, such as Cl, Br and CF3 , were preferred over electron-donating substituents, such as methoxy, and that potency was significantly better when the substituent was in the para-position. Additional investigations showed that bis(anilino)trifluoroethoxytriazines were more potent. Replacement of the remaining trifluoroethyl group in the bis(anilino)triazine series with an alkyl amine lead to compounds of equal or superior efficacy. The work presented showed that electron-withdrawing substituents in the para-position of the aniline ring of the initial hit delivered the best levels of insecticidal potency against the two insect species tested. Further investigations showed that potency could be improved by replacing one of the two trifluoroethoxy groups with additional 4-substituted aniline. This level of potency was maintained or further improved when the remaining trifluoroethoxy was replaced with a substituted amine. © 2017 Society of Chemical Industry.

Dominance of resistance has been one of the major parameters affecting the rate of evolution of resistance to Bt crops. High dose is the capacity of Bt crops to kill heterozygous insects and has been an essential component of the most successful strategy to manage resistance to these crops. Experiments were conducted to evaluate directly and indirectly whether the TC1507 event is high dose to Spodoptera frugiperda (JE Smith). About 8% of heterozygote neonate larvae were able to survive, complete larval development and emerge as normal adults on TC1507 leaves, while susceptible larvae could not survive for 5 days. The estimated dominance of resistance was 0.15 ± 0.09 and significantly higher than zero; therefore, the resistance to Cry1F expressed in TC1507 was not completely recessive. A 25-fold dilution of TC1507 maize leaf tissue in an artificial diet was able to cause a maximum mortality of only 37%, with growth inhibition of 82% at 7 days after larval infestation. Resistance to Cry1F in TC1507 maize is incompletely recessive in S. frugiperda. TC1507 maize is not high dose for S. frugiperda. Additional or alternative resistance management strategies, such as the replacement of single-trait Bt maize with pyramided Bt maize, which produces multiple proteins targeting the same insect pests, should be implemented wherever this technology is in use and S. frugiperda is the major pest.

A modified artificial feeding system was developed for rearing Cimex lectularius and compared with the most widely used artificial feeding method which requires custom-made glassware and a circulating water bath to warm the blood. The petri dish method reduces some of the drawbacks from the current water bath method, such as the possibility of flooding bed bug rearing jars with water or blood and the need for expensive custom-made glassware. Field and lab strain first instar nymphs were given a 15 or 30 min interval to feed for 6-9 weeks. Analysis of bed bugs that fed during a 6 week time period showed that there was no significant difference in the numbers that fed using the petri dish method compared with those that fed using the water bath method. Development of the nymphs also showed that there was no significant difference in the time required to produce adults by either method. The petri dish method is an attractive alternative to the water bath method. Set-up is less complex, quicker, multiple jars of bed bugs can be fed at the same time, petri dishes of blood are disposable for easy clean-up and the potential of fatality due to flooding with blood or water is reduced.

Mechanistic crop models capable of representing realistic temperature responses of key physiological processes are necessary for enhancing our ability to forecast crop yields and develop adaptive cropping solutions for achieving food security in a changing climate. Leaf growth and phenology are critical components of crop growth and yield that are sensitive to climate impacts. We developed a novel modeling approach that incorporates a set of nonlinear functions to augment traditional thermal time methods (e.g., growing degree days) for simulating temperature responses of leaf expansion and phenology in maize or corn (Zea mays L.). The resulting leaf expansion and phenology models have been implemented into a new crop model, MAIZSIM, that simulates crop growth based on key physiological and physical processes including C4 photosynthesis, canopy radiative transfer, C partitioning, water relations, and N dynamics for a maize plant. Coupled with a two‐dimensional soil process model, 2DSOIL, MAIZSIM was applied to simulate leaf growth, phenology, biomass partitioning, and overall growth of maize plants planted at two field sites on the Eastern Shore of Maryland and in Delaware for 3 yr of data. The model parameters were estimated using data from outdoor sunlit growth chambers and the literature. No calibration was performed using the field data. The MAIZSIM model simulated leaf area, leaf addition rate, leaf numbers, biomass partitioning and accumulation with reasonable accuracy. Our study provides a feasible method for integrating nonlinear temperature relationships into crop models that use traditional thermal time approaches without sacrificing their current structure for predicting the climate change impacts on crops.

As part of the regulatory safety assessment for transgenic crops, the DNA of the genetic insert and insert/flanking-region junctions are searched for random reading frames that could encode unsafe proteins. In addition, the endogenous flanking regions are examined to determine if the insert disrupts endogenous genes or regulatory elements. We discuss the likelihood of these events in the context of traditional breeding and in the context of the probability that cryptic reading frames might encode unsafe proteins. We conclude that there is a lack of theoretical and empirical evidence to suggest that these safety risks are significant or different compared with those of traditional crop breeding.