H After Treatment Research Articles

Transcriptomic and Metabolomic Profiling of Root Tissue in Drought-Tolerant and Drought-Susceptible Wheat Genotypes in Response to Water Stress.

Wheat is the most widely grown crop in the world; its production is severely disrupted by increasing water deficit. Plant roots play a crucial role in the uptake of water and perception and transduction of water deficit signals. In the past decade, the mechanisms of drought tolerance have been frequently reported; however, the transcriptome and metabolome regulatory network of root responses to water stress has not been fully understood in wheat. In this study, the global transcriptomic and metabolomics profiles were employed to investigate the mechanisms of roots responding to water stresses using the drought-tolerant (DT) and drought-susceptible (DS) wheat genotypes. The results showed that compared with the control group, wheat roots exposed to polyethylene glycol (PEG) had 25941 differentially expressed genes (DEGs) and more upregulated genes were found in DT (8610) than DS (7141). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs of the drought-tolerant genotype were preferably enriched in the flavonoid biosynthetic process, anthocyanin biosynthesis and suberin biosynthesis. The integrated analysis of the transcriptome and metabolome showed that in DT, the KEGG pathways, including flavonoid biosynthesis and arginine and proline metabolism, were shared by differentially accumulated metabolites (DAMs) and DEGs at 6 h after treatment (HAT) and pathways including alanine, aspartate, glutamate metabolism and carbon metabolism were shared at 48 HAT, while in DS, the KEGG pathways shared by DAMs and DEGs only included arginine and proline metabolism at 6 HAT and the biosynthesis of amino acids at 48 HAT. Our results suggest that the drought-tolerant genotype may relieve the drought stress by producing more ROS scavengers, osmoprotectants, energy and larger roots. Interestingly, hormone signaling plays an important role in promoting the development of larger roots and a higher capability to absorb and transport water in drought-tolerant genotypes.

Comparative transcriptomics analysis of tolerant and sensitive genotypes reveals genes involved in the response to cold stress in bitter gourd (Momordica charantia L.)

Bitter gourd is an economically important horticultural crop for its edible and medicinal value. However, the regulatory mechanisms of bitter gourd in response to cold stress are still poorly elucidated. In this study, phytohormone determination and comparative transcriptome analyses in XY (cold-tolerant) and QF (cold-sensitive) after low temperature treatment were conducted. Under cold stress, the endogenous contents of abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) in XY were significantly increased at 24 h after treatment (HAT), indicating that ABA, JA and SA might function in regulating cold resistance. RNA-seq results revealed that more differentially expressed genes were identified at 6 HAT in QF and 24 HAT in XY, respectively. KEGG analysis suggested that the plant hormone signal transduction pathway was significantly enriched in both genotypes at all the time points. In addition, transcription factors showing different expression patterns between XY and QF were identified, including CBF3, ERF2, NAC90, WRKY51 and WRKY70. Weighted gene co-expression network analysis suggested MARK1, ERF17, UGT74E2, GH3.1 and PPR as hub genes. These results will deepen the understanding of molecular mechanism of bitter gourd in response to cold stress and the identified genes may help to facilitate the genetic improvement of cold-resistant cultivars.

Microbial Community Response to Granular Peroxide-Based Algaecide Treatment of a Cyanobacterial Harmful Algal Bloom in Lake Okeechobee, Florida (USA).

Cyanobacterial harmful algal blooms (cyanoHABs) occur in fresh water globally. These can degrade water quality and produce toxins, resulting in ecological and economic damages. Thus, short-term management methods (i.e., algaecides) are necessary to rapidly mitigate the negative impacts of cyanoHABs. In this study, we assess the efficacy of a hydrogen peroxide-based algaecide (PAK® 27) on a Microcystis dominated bloom which occurred within the Pahokee Marina on Lake Okeechobee, Florida, USA. We observed a significant reduction in chlorophyll a (96.81%), phycocyanin (93.17%), and Microcystis cell counts (99.92%), and a substantial reduction in microcystins (86.7%) 48 h after treatment (HAT). Additionally, there was a significant shift in bacterial community structure 48 HAT, which coincided with an increase in the relative abundance of photosynthetic protists. These results indicate that hydrogen peroxide-based algaecides are an effective treatment method for cyanoHAB control and highlight their effects on non-target microorganisms (i.e., bacteria and protists).

Metabolism of halauxifen acid is regulated by genes located on wheat chromosome 5A

Abstract Allohexaploid wheat (Triticum aestivum L.) is tolerant to halauxifen-methyl (HM) via rapid detoxification of the phytotoxic form of HM, halauxifen acid (HA), to non-phytotoxic metabolites. Previous research utilizing ‘Chinese Spring’ (CS) wheat, alien substitution (i.e., endogenous chromosome pair substituted with a homoeologous pair from diploid Sears’ goatgrass (Aegilops searsii M. Feldman & M. Kislev) (AS), or nullisomic-tetrasomic (NT) lines indicated plants lacking chromosome 5A are more sensitive than CS to HM. We hypothesized the increased HM sensitivity of these plants results from losing gene(s) on chromosome 5A associated with HA metabolism, which leads to a reduced HA detoxification rate relative to CS. To compare HA abundance among AS, CS, alien substitution, and NT lines during a time course, two excised-leaf studies using unlabeled HM and liquid chromatography–mass spectrometry analyses were performed. Aegilops searsii accumulated more HA than CS did, and each substitution line at 8, 12, and 24 h after treatment (HAT). Furthermore, only the wheat substitution line lacking chromosome 5A displayed greater abundance of HA relative to CS (2.4- to 3.8-fold, depending on the time point). In contrast, HA abundances in lines possessing chromosome 5A were not different than HA abundances in CS at all time points. When NT lines were compared with CS, the nullisomic 5D-tetrasomic 5A (N5D-T5A) line displayed similar HA abundance, whereas the nullisomic 5A-tetrasomic 5D (N5A-T5D) accumulated approximately 3-fold more HA at 12 and 24 HAT. These results biochemically support the hypothesis that genes encoding HA-detoxifying enzyme(s) are located on wheat chromosome 5A and corroborate findings from previous greenhouse phenotypic experiments. Future experimentation is needed to identify and characterize genes and enzymes on wheat chromosome 5A involved with HA detoxification, which may include cytochrome P450 monooxygenases, unknown oxidases, UDP-dependent glucosyltransferases, or, potentially, transcription factors that regulate expression of these genes associated with HA detoxification.

Early Detection of Dicamba and 2,4-D Herbicide Drifting Injuries on Soybean with a New Spatial–Spectral Algorithm Based on LeafSpec, an Accurate Touch-Based Hyperspectral Leaf Scanner

In soybeans, off-target damage from the use of dicamba and 2,4-D herbicides for broadleaf weed control can significantly impact sensitive vegetation and crops. The early detection and assessment of such damage are critical for plant diagnostic labs and regulatory agencies to inform regulated usage policies. However, the existing technologies that calculate the average spectrum often struggle to detect and differentiate the damage caused by these herbicides, as they share a similar mode-of-action. In this study, a high-precision spatial and spectral imaging solution was tested for the early detection of dicamba and 2,4-D-induced damage in soybeans. A 2021 study was conducted using LeafSpec, a touch-based hyperspectral leaf scanner, to detect damage on soybean leaves. VIS-NIR (visible–near infrared) hyperspectral images were captured from 180 soybean plants exposed to nine different herbicide treatments at different intervals after spraying. Leaf damage was distinguished as early as 2 h after treatment (HAT) using pairwise partial least squares discriminant analysis (PLS-DA) models based on spectral data. Leaf color distribution, texture, and morphological features were analyzed to separate herbicide dosages. By fully exploiting the spatial and spectral information from high-resolution hyperspectral images, classification accuracy was improved from 57.4% to over 80% for all evaluation dates. This work demonstrates the potential and advantages of using spectral and spatial features of LeafSpec hyperspectral images for the early and accurate detection of herbicide damage in soybean plants.

Comparative effectiveness of biorational pesticides for management of Phenacoccus solenopsis Tinsley and Paracoccus marginatus Williams & Granara de Willink in Gymnema sylvestre (Retz.) R.Br. ex Sm

The cotton mealybug, Phenacoccus solenopsis Tinsley and papaya mealybug, Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) are becoming major threats to the production of Gymnema sylvestre R. Br. (Asclepiadaceae) in India. Management mainly depends on chemical insecticides which cause a serious problem of pesticide residue and insecticide resistance. The use of biorational insecticides such as biopesticides, botanicals, insect growth regulators, and microbial insecticides is important components of an Integrated Pest Management (IPM) program for successful management. We evaluated the bio-efficacy of twelve biorational insecticides, including entomopathogenic fungi (EPF), using the leaf spray method in laboratory conditions at 25 ± 1 °C, 70 % ± 5 % RH. The results revealed that the highest percent mortality was recorded by acetamiprid 20 % SP (100.00 %), followed by azadirachtin (98.27 %), Lecanicillium muscarium (2 × 109 spores/mL) (85.70 %) and Ocimum sanctum leaf extract (76.87 %) at 120 h after treatment (HAT) in P. solenopsis. In P. marginatus, 100.00 %, 96.39 % and 85.67 % and 74.90 % mortalities were achieved by acetamiprid 20 % SP, azadirachtin, L. muscarium (2 × 109 spores/mL) and O. sanctum leaf extract, respectively, at 120 HAT during the first spray. Various biorational insecticides showed a more or less similar trend of percent mortality in both species during the second spray. In both species, the lowest percent mortality was recorded by Andrographis paniculata leaf extract (46.29, 44.54) and (41.03, 46.39) at 120 Hours after treatment in the first and second spray, respectively. It was concluded that all the prescribed treatments are more effective than the control. Overall, azadirachtin recorded the highest percent mortality after acetamiprid and had the shortest LT50 (12.52 h) and (13.87 h) values in P. solenopsis and P. marginatus, respectively. Our study emphasizes that biopesticides like Azadirachtin 1 % EC (10000 ppm), L. muscarium (2 × 109 spores/mL) (5 mL/L) and O. sanctum leaf extract (5 %) may be recommended as alternatives to synthetic insecticides. Botanicals and EPF would be the most effective approach for sustainable integrated management of P. solenopsis and P. marginatus in the G. sylvestre ecosystem.

The influence of priming methods, planting dates, and weed interference levels on the vegetative growth, yield, and yield components of AS71 hybrid corn

By carrying out a laboratory experiment, the influence of priming methods, including ZnSO4, BSN, and hydropriming was evaluated on the seed germination of hybrid AS71 corn. Then, the main and interaction effects of the priming methods, planting dates, and weed interference levels were surveyed on the vegetative growth traits, yield, and yield components of corn in a field experiment. Based on the lab experiment, although the maximum germination percentage (100%) was observed in the treated plots by hydropriming 22 h after treatment (HAT), the greatest seedling vigor index (122.99) was recorded with treated seeds by ZnSO4 (0.03 mg L–1) at 8 HAT. The greatest emergence index was observed in the treated plots by hydropriming on both planting dates of June 1 and 11. The interaction of planting dates and weed interference levels revealed that the highest emergence index (14%–17%) occurred in the weed-free plots on both planting dates. BSN recorded the greatest corn 1000-grain weight that was significantly higher than the control plots by 28%. Furthermore, BSN enhanced the corn grain yield compared with the control plots by 63% and 24.9% on the planting dates of June 1 and 11, respectively. BSN, as a nutri-priming approach, by displaying the highest positive effects in boosting the corn grain yield in both weedy and weed-free plots as well as both planting dates, could be a recommendable option for growers to improve the crop yield production.

Characterization of MCPA resistance in Palmer amaranth (Amaranthus palmeri)

AbstractPhenoxy herbicides (2,4-D and MCPA) are widely used to manage broadleaf weeds including Palmer amaranth (Amaranthus palmeri S. Watson), one of the most troublesome weeds in U.S. cropping systems. Previously, we documented resistance to 2,4-D and MCPA in an A. palmeri population (KCTR) from Kansas. Our recent research suggested rapid metabolism of 2,4-D bestows resistance in KCTR A. palmeri; nonetheless, the mechanism of MCPA resistance in this population is still unknown. The objectives of this research were to (1) evaluate the level of resistance to MCPA in KCTR compared with two known susceptible populations of A. palmeri, MSS and KSS; (2) study the absorption and translocation of [14C]MCPA in KCTR and MSS plants: (3) investigate the metabolic profile of [14C]MCPA in KCTR and MSS and compare those with MCPA-tolerant wheat (Triticum aestivum L.) plants; and (4) assess the possible role of cytochrome P450 enzymes (P450s) in MCPA metabolism. Experiments were conducted to assess the level of resistance in KCTR. Using [14C]MCPA, the absorption, translocation, and metabolic profiles were assessed in A. palmeri. Involvement of P450s was confirmed using malathion, a known P450 inhibitor. Regression analyses indicate that KCTR population exhibits an $\sim $ 3-fold resistance to MCPA. No difference in absorption of [14C]MCPA was found between MSS and KCTR. However, the KCTR plants translocated less [14C]MCPA at 48 h after treatment (HAT) and metabolized MCPA more rapidly than MSS plants at 12 and 24 HAT. MCPA resistance in KCTR was reversed upon treatment with malathion, indicating the involvement of P450s in metabolism of this herbicide. This is the first report of characterization of MCPA resistance in A. palmeri.

Absorption, Translocation, and Metabolism of Glyphosate and Imazethapyr in Smooth Pigweed with Multiple Resistance

The evolution of herbicide-resistant weeds is the major challenge for chemical management worldwide, increasing production costs, and reducing yield. This work aimed to evaluate the putative resistance of the Amaranthus hybridus population from Candido Mota (CMT) to glyphosate and imazethapyr and to investigate the non-target site mechanisms involved. Dose–response studies were conducted under greenhouse conditions and the control and biomass reduction were evaluated 28 days after application (DAA). Absorption, translocation, and metabolization studies were evaluated at 72 h after treatment (HAT) using radiometric techniques. The dose–response results show different responses among populations to glyphosate and imazethapyr. The CMT population was not controlled with labeled herbicide doses. Based on biomass reduction, the resistance factor was 16.4 and 9.4 to glyphosate and imazethapyr, respectively. The CMT absorbed 66% of 14C-glyphosate and 23% of 14C-imazethapyr at 72 HAT. Although the CMT population absorbed more glyphosate than the susceptible population (12.6%), translocation was impaired for both herbicides in the CMT when compared to the SUS population. There was no evidence that herbicide metabolization was involved in CMT resistance to the herbicides studied. Understanding the mechanisms endowing resistance allows better decision-making. This is the first study that describes non-target-site resistance mechanisms in an Amaranthus hybridus population from Brazil.

Exogenous application of a Burkholderia sp. and jasmonic acid at the postharvest stage for management of anthracnose in dessert banana (Musa acuminata)

AbstractThe present study was conducted to determine the potential of controlling natural (latent) and wound infections of anthracnose using a biological control agent (Burkholderia sp. [BS]) and jasmonic acid (JA). Exogenous application of BS (1 × 108 cfu/mL) and JA (0.2 mM) reduced both types of anthracnose in banana cultivars Kolikuttu and Seenikesel within a range of 67.6%–100%. Due to BS and JA treatments, three selected defence genes (β‐1,3‐glucanase, PR‐1 and chitinase) were up‐regulated in the fruit peels of the two banana cultivars over a period of 144 h after treatment (HAT), indicating the ability to induce host plant resistance by the two treatments. BS treatment resulted in a 1.5‐ to 2.5‐fold increase of the above gene transcripts under natural infection in both cultivars. The findings revealed that induction of the three selected defence genes varies depending on the type of the treatment and infection. JA‐treated fruits with natural infections showed a 1‐day delay of ripening and resulted in the lowest ripening indices till 6th day after treatment in comparison to the BS‐ and untreated banana. BS and JA concentrations used in the study, significantly reduced mycelial growth and spore production of C. musae. Lowering of the ripening index, reduction of mycelial growth and spore production of the fungal pathogen and increased expression of the three selected defence genes by BS and JA treatments reduced the disease progression and lesion development of anthracnose in the two banana cultivars under natural and wound infections of C. musae.

Investigations into differential glyphosate sensitivity between two horseweed (Conyza canadensis) growth types

AbstractHorseweed [Conyza canadensis (L.) Cronquist] grows in one of two distinct growth phenotypes, “rosette” and “upright” growth types, and they have recently been observed co-occurring in Michigan fields. Previous research found that upright plants from two glyphosate-resistant populations were 3- and 4-fold less sensitive to glyphosate than their rosette siblings. Further experiments were conducted to investigate whether differential glyphosate sensitivity of the growth types was due to glyphosate retention, absorption, or translocation. The total amount of glyphosate retained on the C. canadensis leaf surface was similar for both growth types; however, on a per-weight and per-area bases, the upright growth type retained 21% and 18% less glyphosate, respectively. Glyphosate absorption was up to 85% at 168 h after treatment (HAT), and was not different between the rosette and upright growth types or between the susceptible (S) and resistant (R) biotypes. Additionally, there was no difference in translocation between the two growth types within each biotype at any time point. Interestingly, at 168 HAT, [14C]glyphosate translocation was higher in the S rosette compared with the two growth types from the R biotype; however, the S upright type was similar to both R growth types. Thus, glyphosate resistance in the R biotype may be due to an alternative mechanism rather than impaired translocation, which has been cited as the primary mechanism of glyphosate resistance in C. canadensis. These results suggest that reduced glyphosate retention on a per-weight and per-area bases of the upright growth type may contribute to increased glyphosate tolerance due to a diluted concentration of glyphosate in the plant. However, another factor is likely related to the mechanism of resistance within the R biotype, which is contributing to a 3-fold difference in glyphosate sensitivity between the two growth types, such as alterations in EPSPS gene expression or changes in undescribed metabolism genes.

Absorption and translocation of [14C]2,4-dichlorophenoxyacetic acid in herbicide-tolerant chromosome substitution lines of Gossypium hirsutum L

Upland cotton is sensitive to 2,4-dichlorophenoxyacetic acid (2,4-D), and spray drift from adjacent crops can cause yield loss. The identification of potentially 2,4-D-tolerant cotton chromosome substitution (CS) lines with well-characterized tolerance mechanisms could provide a significant step into the development and genetic improvement of upland cotton. Experiments were conducted to understand the possible mechanism of herbicide tolerance in CS-T04-15, CS-T07, and CS-B15sh, 2,4-D herbicide-tolerant cotton CS lines compared with TM-1, the 2,4-D herbicide-susceptible recurrent parent of the CS line. Using [ 14 C]2,4-D, the percent absorption rate and the translocation patterns of the 14 C-labeled herbicide at 6 to 48 h after treatment (HAT) were determined. The tolerant cotton CS lines showed 15%–19% [ 14 C]2,4-D uptake, while TM-1 exhibited a reduced uptake of only 1.4% [ 14 C]2,4-D at 24 HAT. Distribution of the absorbed [ 14 C]2,4-D showed that 2%–5% was translocated outside the treated leaf in the tolerant CS lines. In contrast, 77% of the herbicide was translocated above and below the treated leaf in line TM-1. Interestingly, CS-T04-15 showed a restricted movement of 14 C below the treated leaf at 6 to 48 HAT, suggesting novel information on the mechanisms of herbicide tolerance to 2,4-D in cotton. This finding is the first report on upland cotton demonstrating a complex differential uptake and translocation associated with herbicide tolerance for [ 14 C]2,4-D in cotton CS lines.

Improving chemical control of nonnative aquatic plants in run-of-the-river reservoirs

AbstractCurrent dam discharge patterns in Noxon Rapids Reservoir reduce concentration and exposure times (CET) of herbicides used for aquatic plant management. Herbicide applications during periods of low dam discharge may increase herbicide CETs and improve efficacy. Applications of rhodamine WT dye were monitored under peak (736 to 765 m3 s−1) and minimum (1.4 to 2.8 m3 s−1) dam discharge patterns to quantify water-exchange processes. Whole-plot dye half-life under minimal discharge was 33 h, a 15-fold increase compared with the dye treatment during peak discharge. Triclopyr concentrations measured during minimum discharge within the treated plot ranged from 214 ± 25 to 1,243 ± 36 µg L−1 from 0 to 48 h after treatment (HAT), respectively. Endothall concentrations measured during minimum discharge in the same plot ranged from 164 ± 78 to 2,195 ± 1,043 µg L−1 from 0 to 48 HAT, respectively. Eurasian watermilfoil (Myriophyllum spicatum L.) occurrence in the treatment plot was 66%, 8%, and 14% during pretreatment, 5 wk after treatment (WAT), and 52 WAT, respectively. Myriophyllum spicatum occurrence in the nontreated plot was 68%, 71%, and 83% during pretreatment, 5 WAT, and 52 WAT, respectively. Curlyleaf pondweed (Potamogeton crispus L.) occurrence in the treatment plot was 29%, 0%, and 97% during pretreatment, 5 WAT, and 52 WAT, respectively. Potamogeton crispus increased from 24% to 83% at 0 WAT to 52 WAT, respectively, in the nontreated plot. Native species richness declined from 3.3 species per point to 2.1 in the treatment plot in the year of treatment but returned to pretreatment numbers by 52 WAT. Native species richness did not change during the study in the nontreated reference plot. Herbicide applications during periods of low flow can increase CETs and improve control, whereas applications during times of high-water flow would shorten CETs and could result in reduced treatment efficacy.

Resistance to 2,4-D in Palmer amaranth (Amaranthus palmeri) from Kansas is mediated by enhanced metabolism

AbstractA Palmer amaranth (Amaranthus palmeri S. Watson) population (KCTR: KS Conservation Tillage Resistant) collected from a conservation tillage field was confirmed with resistance to herbicides targeting at least six sites of action, including 2,4-D. The objectives of this research were using KCTR A. palmeri to investigate (1) the level of 2,4-D resistance, (2) 2,4-D absorption and translocation profiles, (3) the rate of 2,4-D metabolism compared with 2,4-D–tolerant wheat (Triticum aestivum L.), and (4) the possible role of cytochrome P450s (P450s) in mediating resistance. Dose–response experiments were conducted to assess the level of 2,4-D resistance in KCTR compared with susceptible plants, KSS (KS 2,4-D susceptible) and MSS (MS 2,4-D susceptible). KSS, MSS, and KCTR plants were treated with [14C]2,4-D to determine absorption, translocation, and metabolic patterns. Additionally, whole-plant dose–response assays were conducted by treating KCTR and KSS plants with P450 inhibitors (malathion, piperonyl butoxide [PBO]) before 2,4-D application. Dose–response experiments indicated a 6- to 11-fold 2,4-D resistance in KCTR compared with susceptible plants. No difference was found in percent [14C]2,4-D absorption among the populations. However, 10% less and 3 times slower translocation of [14C]2,4-D was found in KCTR compared with susceptible plants. Importantly, [14C]2,4-D was metabolized faster in KCTR than susceptible plants. At 24, 48, and 72 h after treatment (HAT), KCTR metabolized ∼20% to 30% more [14C]2,4-D than susceptible plants. KCTR plants and wheat generated metabolites with similar polarity. Nonetheless, at 24 HAT, ∼70% of [14C]2,4-D was metabolized in wheat, compared with only 30% in KCTR A. palmeri. Application of malathion before 2,4-D increased the sensitivity to 2,4-D in KCTR, suggesting involvement of P450s in mediating 2,4-D metabolism. However, no such impact of PBO was documented. Overall, this study confirms that enhanced metabolism is the primary mechanism of 2,4-D resistance in KCTR.

Ultrastructural analysis of beetle larva cuticles during infection with the entomopathogenic fungus, Beauveria bassiana.

Beauveria bassiana is one of the commercially available entomopathogenic fungi (EPF), and a number of isolates with high virulence and broad host spectrum have been used to control agricultural and forest pests. Although the functional importance of genes in EPFs' pathogenesis have been extensively studied, the precise ultrastructural mechanism of the fungal infection, particularly penetration of the host insect cuticles, is not well understood. In this study, we investigated the morphology and ultrastructure of the larval cuticle of the red flour beetle, Tribolium castaneum, after treatment with B. bassiana ERL1170 expressing an enhanced green fluorescent protein (Bb-eGFP). The Bb-eGFP showed high virulence against the larvae, with approximately 90% mortality at 48 h after treatment (HAT) and 100% at 72 HAT under our infection conditions. In these larvae, the regions of the body wall with flexible cuticles, such as the ventral and ventrolateral thorax and abdomen, became darkly melanized, but there was little to no melanization in the rigid dorsal cuticular structures. Confocal microscopy and transmission electron microscopy (TEM) indicated that germinated conidia on the surface of the larval cuticle were evident at 6 HAT, which formed penetration pegs and began to penetrate the several cuticle layers/laminae by 12 HAT. The penetration pegs then developed invading hyphae, some of which passed through the cuticle and reached the epidermal cells by 24 HAT. The larval cuticle was aggressively and extensively disrupted by 48 HAT, and a number of outgrowing hyphae were observed at 72 HAT. Our results indicate that Bb-eGFP is capable of infection and penetrating T. castaneum larvae shortly after inoculation (~24 HAT) at the body regions with apparently flexible and membranous cuticles, such as the ventral intersegmental regions and the ventrolateral pleura. This study provides details on the histopathogenesis of the host cuticle by infection and penetration of EPFs, which can facilitate the management of insect pests. © 2022 Society of Chemical Industry.

Changes in 5-Fluorouracil-induced external granular cell damage during the time-course of the developing cerebellum of infant rats.

5-Fluorouracil (5-FU) is widely used as a chemotherapeutic agent that blocks DNA synthesis and replication by inhibiting thymidylate synthetase. This study aimed to elucidate 5-FU-induced changes in the external granular cells (EGCs) in the cerebellum of infant rats and the possible underlying mechanism. Six-day-old infant rats were injected subcutaneously with 40 mg/kg of 5-FU, and their cerebellums were examined at 6, 9, 12, and 24 h after treatment (HAT), and 2, 4, and 10 d after treatment (DAT). The width of the external granular layer (EGL) decreased from 24 HAT to 4 DAT in the 5-FU group compared to that in the control group. However, the width in the 5-FU group was comparable to that of the control group at 10 DAT. The number of apoptotic cells, cleaved caspase 3-labeling index (LI%), p21cip1-LI%, and expression levels of p53, p21cip1, and Fas mRNAs increased at 24 HAT. However, no changes were detected in the expression levels of Puma and Bax mRNAs at any time point. BrdU-LI% increased at 6 and 12 HAT but decreased at 24 HAT. The phospho-histone H3-LI% decreased from 6 HAT to 2 DAT. The width of the molecular layer decreased compared to that of the control group at 10 DAT. No differences were observed in Purkinje cell development. These results indicate that 5-FU inhibited cell proliferation by inducing apoptosis of EGCs via activation of Fas and caspase-3 without the involvement of the mitochondrial pathway and induced p53-dependent G1-S and G2-M phase arrest.

Absorption and Metabolism of Foliar-Applied Rimsulfuron in Potato (Solanum tuberosum L.), Common Lambsquarters (Chenopodium album L.) and Redroot Pigweed (Amaranthus retroflexus L.)

Rimsulfuron is commonly used to control common lambsquarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.) in potato (Solanum tuberosum L.) fields. Comparing rimsulfuron absorption and metabolism patterns in these two weed species with potato could provide crucial information to optimise herbicide application in the field. Hence, an experiment was conducted in Denmark and Iran to evaluate the absorption and metabolism of rimsulfuron at the application rate of 30 g ha−1 in potato, common lambsquarters and redroot pigweed. Seedlings at the 2- to 4-leaf stage were foliar treated with rimsulfluron and plant tissues were harvested at 0, 1, 4, 8, 24 and 48 h after treatment (HAT) to measure the rate of herbicide absorption and metabolism using HPLC. Absorption and metabolism of rimsulfuron differed between potato and weed seedlings. This explains the different susceptibility to rimsulfuron in potato, redroot pigweed and common lambsquarters. Redroot pigweed, the most sensitive species in this study, showed the highest rate of absorption and lowest rate of the herbicide metabolism. Common lambsquarters, a species with an intermediate sensitivity, revealed moderate rimsulfuron absorption and metabolism levels. Potato, the tolerant crop species to rimsulfuron, showed the lowest and highest rate, respectively, of absorption and metabolism.

Influence of temperature on the retention, absorption and translocation of fomesafen and imazamox in Euphorbia heterophylla

Climate change will be an additional issue to the challenge to manage herbicide resistant weeds. This work investigated the impact of three temperature regimes (10/5, 20/15 and 30/25 °C) on the efficacy, foliar retention, absorption and translocation of fomesafen, protoporphyrinogen oxidase (PPO) inhibitor, and imazamox, acetolactate synthase (ALS) inhibitor, between two Euphorbia heterophylla populations, one susceptible (S) and one multiple PPO and ALS resistant (R). The R population went from 5 (fomesafen) and 12 (imazamox) times more resistant than the S population at 10/5 °C to more than 100 times to both herbicides at 20/15 and 30/25 °C. Leaf retention of fomesafen was not affected by temperature; however, imazamox retention was less at 10/5 and 20/15 °C than at 30/25 °C, and the R population always retained less imazamox than the S population. 14C-fomesafen absorption was similar between populations, but lower amounts were absorbed at 10/5 °C regardless of the evaluation time. Recovered 14C-imazamox rates decreased in both populations as the evaluation time increased, ranging from 82 to 92% at 6 h after treatment (HAT), and from 47 to 76% at 48 HAT, depending on the temperature regime. The 14C-imazamox losses were greater from 24 HAT in R plants grown at 30/25 °C and in all temperature regimes at 48 HAT. Although both populations translocated large amounts of imazamox, the S population distributed it in the rest of the plant (33%) and roots (15%), while the R population kept it mainly on the treated leaf (24%) or lost ~20% more herbicide than S population at 48 HAT, indicating the need for further studies on root exudation between these populations. Low temperatures reduced resistance levels to fomesafen and imazamox in E. heterophylla, suggesting that temperature influences the expression of the mechanisms that govern this multiple resistance.

Tolerance to Some ACCase Inhibitors in Four Common Roegneria (Roegneria kamoji) Populations From China

Common roegneria, a perennial weed in Roegneria genera of the tribe Triticeae (family: Poaceae), is widely distributed in China and could not be effectively controlled by Acetyl coA carboxylase (ACCase) inhibitors in wheat in some regions. This study aimed to quantify herbicide tolerance level and investigate its mechanisms of ACCase tolerance in common roegneria. Whole-plant dose-response assay indicated that populations ZJJX and HBJZ (collected in wheat fields) exhibited high tolerance (ED50s>16-fold labeled field rate, LFR) to fenoxaprop-P-ethyl and clodinafop- propargyl (aryloxyphenoxypropionate, APPs), and pinoxaden (phenylpyrazolin, DEN). In addition, two populations collected from uncultivated areas, showed similar responses to these herbicides. All common roegneria populations were susceptible to haloxyfop-R-methyl and quizalofop-p-ethyl (APPs), clethodim and sethoxydim (cyclohexanedione, CHDs) (ED50s<1/2-fold LFR). The responses to ACCase inhibitors of common roegneria were in complete accord with wheat. ACCase sequencing revealed that the APPs tolerance was not conferred by known amino acid substitutions. The sensitivity of common roegneria populations to fenoxaprop-P-ethyl could not be reduced by metabolic inhibitors malathion and 4-chloro-7-nitro-benzoxadiazole. In vitro ACCase enzyme activity assays revealed that the activities of ACCase were increased in ZJJX, ZJHZ populations and wheat after fenoxaprop-P-ehtyl treatment, which at 72 h after treatment (HAT) was 1.46, 1.39 and 1.34-folds higher than that at 0 HAT, respectively. To our knowledge, this study reported for the first time the natural tolerance to ACCase inhibitors in common roegneria. The enhanced ACCase activity suggested that rapid metabolism of the herbicide might play an important role in the tolerance mechanism of this weed. Rotated with other crops (i.e. oilseed rape) to use different herbicides could serve as important tools for managing common roegneria in wheat.

Metabolic resistance to S-metolachlor in two waterhemp (Amaranthus tuberculatus) populations from Illinois, USA.

Two waterhemp (Amaranthus tuberculatus) populations from Illinois demonstrating multiple-resistance to acetolactate synthase (ALS)-, 4-hydroxyphenylpyruvate dioxygenase, and photosystem II (PSII)-inhibiting herbicides (designated CHR and SIR) also displayed reduced sensitivity to very-long-chain fatty acid-inhibiting herbicides, including S-metolachlor. We hypothesized that a physiological mechanism, such as enhanced metabolism, could be responsible for the reduced efficacy of S-metolachlor. Metabolism experiments indicated that resistant populations degraded S-metolachlor more rapidly than sensitive populations and equally as rapidly as corn 2-24 h after treatment (HAT). Resistant waterhemp and corn metabolized 90% (DT90 ) of absorbed S-metolachlor in less than 3.2 h whereas DT90 values for sensitive waterhemp exceeded 6 h. The glutathione S-transferase inhibitor 4-chloro-7-nitrobenzofurazon and cytochrome P450-inhibitor malathion decreased the amount of S-metolachlor metabolized in resistant waterhemp at 4 HAT but not in sensitive waterhemp or corn, and altered the abundance of certain metabolites in resistant waterhemp. Results from this research demonstrate that resistance to S-metolachlor in these waterhemp populations is due to enhanced herbicide metabolism relative to sensitive populations. In addition, our results indicate that resistant waterhemp might utilize metabolic pathway(s) more intricate than either sensitive waterhemp or corn based on their metabolite profiles. © 2020 Society of Chemical Industry.