Do fall armyworm’s Metaflumizone resistante populations affect the activity of Trichogramma pretiosum?

The possible interference of resistant pest’s populations to insecticides in natural enemies in the action thas not been clarified yet. Thus, this study aimed to evaluate Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) performance on Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) eggs with resistance frequency to the Metaflumizone over six generations of product exposure. Egg cards (2.0 x 7.0 cm) containing eggs from two populations of S. frugiperda, (resistant to Metaflumizone and the other susceptible), were exposed to T. pretiosum females for 24 hours in free-choice and no-choice testing in three generations (G1, G4, and G6). A completely randomized experimental design was used with 25 replications, each consisting of an egg card (experimental unit) containing 20 eggs. The parameters evaluated were: parasitism (%), emergence (%), sex ratio, number of emerged parasitoids per egg and males/females longevity. ANOVA and Tukey test (P≤ 0.05) were applied on the results. Results showed a reduction in parasitism [41.0% (G1) and 28.4% (G4)], egg emergence (17.5%) and parasitoids/egg [16.2 (G4) and 17.2 (G6)] in eggs originating from the population with resistance frequency. Females emerging from G6 populations eggs without exposure to Metaflumizone had greater longevity (3.5 days more) than the resistant population. The sex ratio and male longevity were not affected. The results indicate a reduction in T. pretiosum activity if S. frugiperda populations have some frequency of resistance to Metaflumizone.

Population Dynamics of Hybrid State during Adaptive Therapy in Cancer

Drug resistance emerges due to drug-induced phenotypic switching of drug-sensitive to drug-resistant subpopulations in cancer during therapy. Existing models indicate the competitive advantage of sensitive over resistant population to regulate tumor and reducing the treatment cost with increased time to progression of tumor ultimately benefiting the patient in a clinical setting. Here, we present a Lotka Volterra (LV) based population dynamics (PD) model of the drug-sensitive, drug-resistant, and transient drug-hybrid state along with phenotypic switching during adaptive therapy based on a simple cancer biomarker (CB) to decide the adaptive therapy dosage to regulate cancer. We identified that the strength of intra-competition along with phenotypic switching parameters is crucial to mediate the effectiveness of adaptive therapy and also investigated the significance of the initial fraction of subpopulations on AT. We hypothesize and predict the dynamics of drug-induced transient hybrid state playing a key role in the cancer cells undergoing metastasis.

Wheat Density Alters but Does Not Repress the Expression of a Fluroxypyr-Resistant Kochia (Bassia scoparia) Phenotype

Dose-response experiments for confirmation of herbicide-resistant weeds are almost always conducted using weed monocultures, thereby ignoring the interaction of interspecific plant interference with herbicide efficacy. Controlled-environment dose-response bioassays were conducted using three kochia [Bassia scoparia (L.) A.J. Scott] populations with four spring wheat (Triticum aestivum L.) densities (0, 200, 400, and 600 plants m−2) to determine how increasing intensity of interspecific plant interference altered the fluroxypyr dose-response relationship of resistant and susceptible kochia. The resistant population exhibited 10.8-, 15.0-, 7.0-, and 8.1-fold resistance to fluroxypyr in the absence of crop interference based on plant survival, biomass fresh weight, and visible control at two and four weeks after application, respectively. Increased wheat densities suppressed fluroxypyr-resistant kochia the greatest, resulting in a linear reduction in the fluroxypyr rate causing 50% plant mortality (LD50) and visible control (ED50) for the resistant but not the susceptible populations. This reduced the expression of fluroxypyr resistance based on kochia plant survival (from 10.8- to 4.3-fold resistance) and visible control (from 8.1- to 4.6-fold resistance) as wheat density increased from 0 to 600 plants m−2. Therefore, enhanced interspecific plant interference caused by increased wheat densities altered but did not repress the expression of fluroxypyr resistance in kochia.

Seeking Alfalfa Resistance to a Rhizophagous Pest, the Clover Root Curculio (Sitona hispidulus F.)

Since the cancellation of broad-spectrum soil-active insecticides in alfalfa (Medicago sativa L.) production, clover root curculio (Sitona hispidulus F.) (CRC) larval root damage has increased. Current CRC management practices are limited in their ability to suppress larval feeding belowground. First, we field screened developmental alfalfa populations for CRC damage. Subsequently, we developed a soil-less arena to observe nodule feeding and development (head capsule width) of larvae in the lab. This method was used to evaluate five alfalfa populations (two CRC-susceptible (control) and three CRC-resistant populations) against larvae. Further, one CRC-resistant population paired with its genetically similar susceptible population were tested against adult leaf consumption and oviposition in the greenhouse. Field screening revealed that the alfalfa populations selected for little or no larval root feeding damage were more resistant to CRC larval feeding than their corresponding unselected cultivars and significantly more resistant than populations selected for susceptibility. The development of a soil-less arena provided a useful method for evaluation of root-larva interactions. Although larval development was similar across susceptible and resistant alfalfa populations, one CRC-resistant population (NY1713) displayed overall increased nodulation and, thus, had a significantly lower proportion of nodules consumed by larvae. Adult feeding and oviposition aboveground were similar across all populations tested. These results provide possible candidates and screening method for the development and evaluation of alfalfa cultivars that may reduce the impacts of larval feeding and that offer an additional option for CRC management.

Heterogeneous A40926 Self-Resistance Profile in Nonomuraea gerenzanensis Population Informs Strain Improvement

Nonomuraea gerenzanensis ATCC 39727 produces the glycopeptide antibiotic A40926, which is the natural precursor of the semi-synthetic, last-resort drug dalbavancin. To reduce the cost of dalbavancin production, it is mandatory to improve the productivity of the producing strain. Here, we report that the exposure of N. gerenzanensis wild-type population to sub-inhibitory concentrations of A40926 led to the isolation of differently resistant phenotypes to which a diverse A40926 productivity was associated. The most resistant population (G, grand colonies) represented at least the 20% of the colonies growing on 2 µg/mL of A40926. It showed a stable phenotype after sub-culturing and a homogeneous profile of self-resistance to A40926 in population analysis profile (PAP) experiments. The less resistant population (P, petit) was represented by slow-growing colonies to which a lower A40926 productivity was associated. At bioreactor scale, the G variant produced twice more than the wild-type (ca. 400 mg/L A40926 versus less than 200 mg/L, respectively), paving the way for a rational strain improvement based on the selection of increasingly self-resistant colonies.

Cancer stem cell phosphatases

Cancer stem cells (CSCs) are involved in the initiation and progression of human malignancies by enabling cancer tissue self-renewal capacity and constituting the therapy-resistant population of tumor cells. However, despite the exhausting characterization of CSC genetics, epigenetics, and kinase signaling, eradication of CSCs remains an unattainable goal in most human malignancies. While phosphatases contribute equally with kinases to cellular phosphoregulation, our understanding of phosphatases in CSCs lags severely behind our knowledge about other CSC signaling mechanisms. Many cancer-relevant phosphatases have recently become druggable, indicating that further understanding of the CSC phosphatases might provide novel therapeutic opportunities. This review summarizes the current knowledge about fundamental, but yet poorly understood involvement of phosphatases in the regulation of major CSC signaling pathways. We also review the functional roles of phosphatases in CSC self-renewal, cancer progression, and therapy resistance; focusing particularly on hematological cancers and glioblastoma. We further discuss the small molecule targeting of CSC phosphatases and their therapeutic potential in cancer combination therapies.

Fate and adaptive plasticity of heterogeneous resistant population of Echinochloa colona in response to glyphosate

Understanding the fate of heterogenous herbicide resistant weed populations in response to management practices can help towards overcoming the resistance issues. We selected one pair of susceptible (S) and resistant (R) phenotypes (2B21-R vs 2B21-S and 2B37-R vs 2B37-S) separately from two glyphosate resistant heterogeneous populations (2B21 and 2B37) of Echinochloa colona and their fate and adaptive plasticity were evaluated after glyphosate application. Our study revealed the glyphosate concentration required to cause a 50% plant mortality (LD50) was 1187, 200, 3064, and 192 g a. e. ha−1 for the four phenotypes 2B21-R, 2B21-S, 2B37-R, and 2B37-S respectively. Both S phenotypes accumulated more biomass than the R phenotypes at the lower application rates (34 and 67.5 g a. e. ha−1) of glyphosate. However, the R phenotypes generally produced more biomass at rates of glyphosate higher than 100 g a. e. ha−1 throughout the growth period. Plants from the R phenotypes of 2B21 and 2B37 generated 32% and 38% fewer spikesplant−1 than their respective S counterparts in the absence of glyphosate respectively. The spike and seed numbersplant-1 significantly higher in R than S phenotypes at increased rates of glyphosate and these relationships were significant. Our research suggests that glyphosate-resistant E. colona plants will be less fit than susceptible plants (from the same population) in the absence of glyphosate. But in the presence of glyphosate, the R plants may eventually dominate in the field. The use of glyphosate is widespread in field, would favour the selection towards resistant individuals.

Effectiveness of glufosinate, dicamba, and clethodim on glyphosate-resistant and susceptible populations of five key weeds in Australian cotton systems

XtendFlexTM cotton with resistance to glyphosate, glufosinate and dicamba may become available in Australia. Resistance to these herbicides enables two additional modes of action to be applied in crop. The double knock strategy, typically glyphosate followed by paraquat, has been a successful tactic for control of glyphosate-resistant in fallow situations in Australia. Glufosinate is a contact herbicide, and may be useful as the second herbicide in a double knock for use in XtendFlexTM cotton crops. We tested the effectiveness of glufosinate applied at intervals of 1, 3, 7, and 10 d after initial applications of glyphosate, dicamba, clethodim and glyphosate mixtures with dicamba or clethodim on glyphosate-resistant and susceptible populations of Conyza bonariensis, Sonchus oleraceus, Chloris virgata, Chloris truncata and Echinochloa colona. Effective treatments for Conyza bonariensis with 100% control were dicamba and glyphosate+dicamba followed by glufosinate independent of the interval between applications. Sonchus oleraceus was effectively controlled in Experiment 1 by all treatments. However, in Experiment 2 effective treatments were dicamba and glyphosate+dicamba followed by glufosinate (99.3 – 100% control). Timing of the follow-up glufosinate did not affect the control achieved. Consistent control of Chloris virgata was achieved with glyphosate, clethodim or glyphosate+clethodim followed by glufosinate at 7 and 10 d intervals (99.7 – 100% control). Control of Chloris truncata was inconsistent. The best treatment for C. truncata was glyphosate+clethodim followed by glufosinate 10 d later (99.8 – 100% control). Echinochloa colona was effectively controlled with all treatments except for glyphosate on the glyphosate-resistant population. Additional in-crop use of glufosinate and dicamba should be beneficial for weed management in XtendFlexTM cotton crops, when utilising the double knock tactic with glufosinate. For effective herbicide resistance management, it is important that these herbicides be used in addition to, rather than substitution for, existing weed management tactics.

Combined State and Parameter Identifiability for a Model of Drug-Resistant Cancer Dynamics

This article analyzes the combined parameter and state identifiability for a model of a cancerous tumor's growth dynamics. The model describes the impact of drug administration on the growth of two populations of cancer cells: a drug-sensitive population and a drug-resistant population. The model's dynamic behavior depends on the underlying values of its state variables and parameters, including the initial sizes and growth rates of the drug sensitive and drug-resistant populations, respectively. The article's primary goal is to use Fisher identifiability analysis to derive and analyze the Cram´er-Rao theoretical bounds on the best-achievable accuracy with which this estimation can be performed locally. This extends previous work by the authors, which focused solely on state estimation accuracy. This analysis highlights two key scenarios where estimation accuracy is particularly poor. First, a critical drug administration rate exists where the model's state observability is lost, thereby making the independent estimation of the drug-sensitive and drug-resistant population sizes impossible. Second, a different critical drug administration rate exists that brings the overall growth rate of the drug-sensitive population to zero, thereby worsening model parameter identifiability.