Effects of injudicious use of spirotetramat on Encarsia formosa's ability to control Bemisia tabaci.

The excessive and frequent use of insecticides has led to serious problems with insecticide residues, impacting nontarget organisms such as the parasitoid Encarsia formosa. This study examined the growth, development, and enzyme activity of E. formosa exposed to spirotetramat at LC10, LC30, and LC50. The regression equation for the toxicity of spirotetramat toward E. formosa was Y = 5.25X-11.07. After exposure to spirotetramat, the survival rates of E. formosa sharply decreased, which occurred earlier than those in the control batch. Although the maximum daily parasitism quantity of E. formosa increased and the average parasitism number, enumerated from the 1st to the 5th day, was 53.97 after being exposed to spirotetramat at LC10, the life span of its F1 generation adults was only 8.47 days, which was significantly shorter than that in the control batch. After being exposed to spirotetramat at LC50, the average parasitism number of E. formosa was 63.30, and the developmental time of its F1 generation, enumerated from the 1st to the 5th day after exposure to spirotetramat, was significantly longer than that of the control batch. The activities of mixed function oxidase, acetylcholinesterase, carboxylesterase, and catalase increased significantly, and the rate of increase in enzyme activity was directly proportional to the increase in the concentration of spirotetramat. These results revealed that the parasitic ability of E. formosa decreased after exposure to spirotetramat at LC10, LC30, and LC50. This leads to a change in parasitoid control of pests, revealing the potential environmental threat of insecticide residues to nontarget organisms.

Response of growth and physiological enzyme activities in Eriogyna pyretorum to various host plants.

Morphological attributes and chemical composition of host plants shape growth and development of phytophagous insects via influences on their behavior and physiological processes. This research delves into the relationship between Eriogyna pyretorum and various host plants through studuying how feeding on different host tree species affect growth, development, and physiological enzyme activities. We examined E. pyretorum response to three distinct host plants: Camphora officinarum, Liquidambar formosana and Pterocarya stenoptera. Notably, larvae feeding on C. officinarum and L. formosana displayed accelerated development, increased pupal length, and higher survival rates compared to those on P. stenoptera. This underlines the pivotal role of host plant selection in shaping the E. pyretorum's life cycle. The activities of a-amylase, lipase and protective enzymes were the highest in larvae fed on the most suitable host L. formosana which indicated that the increase of these enzyme activities was closely related to growth and development. Furthermore, our investigation revealed a relationship between enzymatic activities and host plants. Digestive enzymes, protective enzymes, and detoxifying enzymes exhibited substantial variations contingent upon the ingested host plant. Moreover, the total phenolics content in the host plant leaves manifested a noteworthy positive correlation with catalase and lipase activities. In contrast, a marked negative correlation emerged with glutathione S-transferase and α-amylase activities. The total developmental duration of larvae exhibited a significant positive correlation with the activities of GST and CarE. The survival rate of larvae showed a significant positive correlation with CYP450. These observations underscore the insect's remarkable adaptability in orchestrating metabolic processes in accordance with available nutritional resources. This study highlights the interplay between E. pyretorum and its host plants, offering novel insights into how different vegetation types influence growth, development, and physiological responses. These findings contribute to a deeper comprehension of insect-plant interactions, with potential applications in pest management and ecological conservation.

Effects of CO2 elevation on life-history traits of two insecticide-resistant strains of planthopper Nilaparvata lugens on rice.

We made separate experiments to examine life-history traits and activities of protective enzymes as affected by carbon dioxide (CO2) elevation to 780 µL/L as compared to 390 µL/L in imidacloprid- or buprofezin-resistant strains of the brown planthopper (BPH) Nilaparvata lugens. We found an interaction effect between resistance and the CO2 level on the nymphal survival and duration in both resistant strains. Nymphal durations in both resistant strains were much shorter in the resistant than susceptible BPH at 780 µL/L but similar between them or slightly shorter in the resistant than susceptible BPH at 390 µL/L. Nymphal survival was lower for imidacloprid-resistant than its susceptible BPH at 390 µL/L but higher at 780 µL/L; it stayed unaffected by the CO2 elevation in buprofezin-resistant BPH. We did not observe an interaction effect between resistance and the CO2 level on major reproductive parameters in both resistant strains. But the 2 strains were not consistent across CO2 levels in all parameters. Our measurements of protective enzyme activities of superoxide dismutase, catalase, and peroxidase showed an interaction between resistance and the CO2 level. Overall, these enzymes became similar in activity between resistant and susceptible BPH at 780 µL/L compared to 390 µL/L and the change was more distinct in the imidacloprid- than buprofezin-resistant BPH strains. Our findings suggest that CO2 elevation can affect life-history traits of insecticide-resistant BPH, while the effect may vary depending on the kind of insecticides it is resistant to.

The immune response of Locusta migratoria manilensis at different times of infection with Paranosema locustae.

Paranosema locustae is an entomopathogenic microsporidia with promising potential for controlling agricultural pests, including Locusta migratoria manilensis. However, it has the disadvantage of having a slow insecticidal rate, and how P. locustae infection impacts the host immune response is currently unknown. The present study investigated the effect of P. locustae on the natural immune response of L. migratoria and the activities of enzymes that protect against oxidative stress. Infection with P. locustae increased the hemocytes and nodulation number of L. migratoria at the initial stage of infection. The hemocyte-mediated modulation of immune response was also affected by a decrease in the number of hemocytes 12 days postinfection. Superoxide dismutase activity in locusts increased in the early stages of infection but decreased in the later stages, whereas the activities of peroxidase (POD) and catalase (CAT) showed opposite trends may be due to their different mechanisms of action. Furthermore, the transcription levels of mRNA of antimicrobial peptide-related genes and phenoloxidase activity in hemolymph in L. migratoria were suppressed within 15 days of P. locustae infection. Overall, our data suggest that P. locustae create a conducive environment for its own proliferation in the host by disrupting the immune defense against it. These findings provide useful information for the potential application of P. locustae as a biocontrol agent.

Role of the Subtilisin-like Serine Protease CJPRB from Cordyceps javanica in Eliciting an Immune Response in Hyphantria cunea.

Hyphantria cunea is a globally distributed quarantine plant pest. In a previous study, the Cordyceps javanica strain BE01 with a strong pathogenic effect on H. cunea was identified, and overexpression of the subtilisin-like serine protease CJPRB of this strain was found to accelerate the death of H. cunea (previous research results). In this study, the active recombinant CJPRB protein was obtained through the Pichia pastoris expression system. It was found that CJPRB protein administration to H. cunea via infectation, feeding and injection was able to induce changes in protective enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and polyphenol oxidase (PPO), and the expression of immune defense-related genes in H. cunea. In particular, CJPRB protein injection induced a more rapid, widespread and intense immune response in H. cunea compared to the other two treatment methods. The results suggest that the CJPRB protein may play a role in eliciting a host immune response during infectation by C. javanica.

Use of plant growth regulators to reduce 2-methyl-4-chlorophenoxy acetic acid-Na (MPCA-Na) damage in cotton (Gossypium hirsutum).

BACKGROUND: 2-methyl-4-chlorophenoxy acetic acid-Na (MPCA-Na) is a phenoxy carboxylic acid selective hormone herbicide that is widely used in the crop fields. However, drift of MPCA-Na during application is highly damaging to cotton (Gossypium hirsutum) and other crop plants. This study was carried out from 2019 to 2020 to determine the effects of different concentrations of MPCA-Na on physiological and metabolic activities besides growth and yield of cotton plants at seedling, budding, flowering and boll stages. Moreover, we evaluated the different combinations of 24-epibrassinolide, gibberellin (GA3), phthalanilic acid and seaweed fertilizer to ameliorate herbicide damage. RESULTS: 2-methyl-4-chlorophenoxy acetic acid-Na (MPCA-Na) exposure caused a decrease in the chlorophyll content, and an increase in the soluble protein content, Malondialdehyde (MDA) content and protective enzyme activity. It also caused significant reductions in plant height, boll number and the single boll weight at the seedling and budding stages, but had little effects on plant height and the single boll weight at flowering and boll stage. Under the maximum recommended dose of MPCA-Na (130 g/L), the number of cotton bolls at seedling and budding stages decreased by 75.33 and 79.50%, respectively, and the single boll weight decreased by 46.42 and 36.31%, respectively. Nevertheless, the number of G. hirsutum bolls and single boll weight at flowering and boll stage decreased by 48.15 and 5.38%, respectively. Application of plant growth regulators decreased the MDA content, and increased chlorophyll, soluble protein content and protective enzyme activity, and alleviated MCPA-Na toxicity. Positive effects in case of growth regulators treated plants were also observed in terms of G. hirsutum yield. Phthalanilic acid + seaweed fertilizer, 24-epibrassinolide + seaweed fertilizer, and GA3 + seaweed fertilizer should be used at the seedling, budding, and flowering and boll stages, respectively. CONCLUSIONS: The results of current study suggest that certain plant growth regulators could be used to alleviate MPCA-Na damage and maintain G. hirsutum yield. When the cotton exposed to MCPA-Na at the seedling stage, it should be treated with phthalanilic acid + seaweed fertilizer, while plants exposed at the budding stage should be treated with 24-epibrassinolide + seaweed fertilizer, and those exposed at the flowering and boll stages should be treated with GA3 + seaweed fertilizer to mitigate stress.

Increasing the activities of protective enzymes is an important strategy to improve resistance in cucumber to powdery mildew disease and melon aphid under different infection/infestation patterns.

Powdery mildew, caused by Sphaerotheca fuliginea (Schlecht.) Poll., and melon aphids (Aphis gossypii Glover) are a typical disease and insect pest, respectively, that affect cucumber production. Powdery mildew and melon aphid often occur together in greenhouse production, resulting in a reduction in cucumber yield. At present there are no reports on the physiological and biochemical effects of the combined disease and pest infection/infestation on cucumber. This study explored how cucumbers can regulate photosynthesis, protective enzyme activity, and basic metabolism to resist the fungal disease and aphids. After powdery mildew infection, the chlorophyll and free proline contents in cucumber leaves decreased, while the activities of POD (peroxidase) and SOD (superoxide dismutase) and the soluble protein and MDA (malondialdehyde) contents increased. Cucumber plants resist aphid attack by increasing the rates of photosynthesis and basal metabolism, and also by increasing the activities of protective enzymes. The combination of powdery mildew infection and aphid infestation reduced photosynthesis and basal metabolism in cucumber plants, although the activities of several protective enzymes increased. Aphid attack after powdery mildew infection or powdery mildew infection after aphid attack had the opposite effect on photosynthesis, protective enzyme activity, and basal metabolism regulation. Azoxystrobin and imidacloprid increased the contents of chlorophyll, free proline, and soluble protein, increased SOD activity, and decreased the MDA content in cucumber leaves. However, these compounds had the opposite effect on the soluble sugar content and POD and CAT (catalase) activities. The mixed ratio of the two single agents could improve the resistance of cucumber to the combined infection of powdery mildew and aphids. These results show that cucumber can enhance its pest/pathogen resistance by changing physiological metabolism when exposed to a complex infection system of pathogenic microorganisms and insect pests.

Potassium application promote cotton acclimation to soil waterlogging stress by regulating endogenous protective enzymes activities and hormones contents.

To investigate the effect of potassium application on cotton damage mitigation after waterlogging stress, experiments were conducted under two potassium application levels (0 and 150 kg K2O hm-2) with three types of soil waterlogging treatments (0d, 3d and 6d) during cotton flowering stage. The results showed that: (a) under simple soil waterlogging stress, the increments of endogenous hormones contents of IAA, GA3 and ZR in cotton leaves were decreased as days of soil waterlogging. On the contrary, the soluble protein, MDA and ABA contents were significantly increased, while ZR/ABA, IAA/ABA and GA3/ABA were decreased. CAT and POD enzyme activities were increased although SOD activity decreased with the duration of soil waterlogging. (b) Potassium application combined with soil waterlogging significantly affected the antioxidant enzymes activity and endogenous hormones balance compared with soil waterlogging alone, leading to a significant increase in soluble protein and a pronounced decrease in H2O2 content, O2- generation rate, and MDA content, a significant increase in IAA, GA3 and ZR contents while a decrease in ABA content. Besides, it also kept higher SOD, CAT activities and slowly increased POD activity. (c) There was an obvious compensatory effect in cotton after 3d soil waterlogging under potassium application, which promoted rapidly recovery of physiological enzymes activities and ABA content. However, 6d soil waterlogging required a longer time for recovery. These findings were expected to provide a scientific and theoretical basis for reducing flood damage and improving cotton yield.

The effects of mepiquat chloride (DPC) on the soluble protein content and the activities of protective enzymes in cotton in response to aphid feeding and on the activities of detoxifying enzymes in aphids.

BACKGROUND: Mepiquat chloride (DPC) enhances the resistance of cotton plants, and it is widely used as a growth regulator. DPC can stimulate photosynthesis, stabilize the structure of cotton leaves, and affect population reproduction and energy substances in Aphis gossypii Glover (cotton aphids), but interactions between DPC and cotton aphids remain unclear. In this study, we analyzed the physiological responses of cotton to DPC, and the toxicity of DPC toward cotton aphids, before and after feeding, to explore the DPC-induced defense mechanism against cotton aphids. RESULTS: Measurements of protective enzyme activity in cotton showed that the soluble protein contents, peroxidase (POD) activity, and catalase (CAT) activity in cotton treated with different concentrations of DPC were higher than in the control. Superoxide dismutase (SOD) activity was higher than that of the control when the concentration of DPC was < 0.1 g/L. Under aphid feeding stress, POD activity in cotton treated with a low insect population density was significantly lower than in the controls, but the reverse was true for cotton treated with a high insect population density, and SOD activity was positively correlated with population density. The activities of detoxification enzymes in field and laboratory experiments showed that DPC promoted the specific activity of glutathione S-transferase (GST) in cotton aphids, while the specific activities of carboxylesterase (CarE) and acetylcholinesterase (AchE) were decreased. CONCLUSIONS: DPC enhanced the aphid resistance in cotton by increasing the soluble protein content and the activity of protective enzymes. It also had a toxic effect on cotton aphids by increasing GST activity (the main DPC target). DPC increased the soluble protein content and protective enzymes activity in cotton under aphid stress, and thereby enhanced tolerance to cotton aphids. It conclude that DPC interferes with cotton aphids through indirect (DPC induced cotton defense responses) and direct (DPC toxicity to cotton aphids) ways, which plays a positive role in interfering with cotton aphids.

Roots play a key role in drought-tolerance of poplars as suggested by reciprocal grafting between male and female clones.

Drought stress influences the growth of plants and thus grafting has been widely used to improve tolerance to abiotic stresses. Poplars possess sex-specific responses to drought stress, but how male or female rootstock affect the grafted plant is little known. To explore the mechanisms underlying changes in drought tolerance caused by grafting, we investigated the changes in growth, leaf traits, gas exchange and antioxidant enzyme activities of reciprocally grafted seedlings between Populus euramericana cv. "Nanlin895" (NL-895) (female) and Populus deltiodes cv."3412" (NL-3412) (male) under water deficit stress with 30% field capacity for 30 d. Results showed that drought stress affected adversely growth, morphological, and physiological characteristics in all seedlings studied. Grafted seedlings with male roots can effectively alleviated the inhibition of growth induced by drought stress, as shown by higher WUE, activities of SOD, POD and CAT, and lower levels of lipid peroxidation. Male seedlings with female roots were found to be less tolerance to drought than non-grafted male clones and female scions with male roots, but more tolerance than non-grafted female clones. This results suggested that drought tolerance of grafted seedlings is primarily caused by the rootstock, although the scion also affects the grafted plant. Thus, paying attention on the root genotype can provide an important means of improving the drought tolerance of poplars.

CIP elicitors on the defense response of A. macrocephala and its related gene expression analysis.

Plant-derived elicitor is a new type of plant vaccine developed in the contemporary era, and it has safe and broad application prospects in organic agriculture. Research on defense mechanisms triggered by elicitor has become a hot topic in recent years. The Chrysanthemum indicum polysaccharide (CIP) obtained by separation and purification from Chrysanthemum indicum was used as an elicitor in this work. This elicitor has been shown to be effective in Atractylodes macrocephala Koidz (A. macrocephala) against Sclerotium rolfsii sacc (S. rolfsii) infection and soil-borne diseases. However, the mechanism of induced disease resistance has not been elucidated. In this research, we study the CIP-induced A. macrocephala defense response from the level of signal molecules and the defensive enzyme gene expression. Several defense responses to CIP treatment have been found in A. macrocephala, including early hydrogen peroxide (H2O2) production, accumulation of salicylic acid (SA) and increased phytoalexin (PA) content. In addition, CIP significantly increased the activity of related defense enzymes in A. macrocephala. RT-qPCR analysis showed that defense-related genes such as polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were up-regulated after CIP treatment. To obtain the sequence of the defense enzyme gene, we are the first to provide a public and comprehensive A. macrocephala database by transcriptome sequencing. These results together demonstrate that CIP triggers defense responses in A. macrocephala. Our research not only provides further research on immune mechanism between plant and elicitor, but also sheds new light on strategy for biocontrol in the future.

Effects of Lecanicillium lecanii strain JMC-01 on the physiology, biochemistry, and mortality of Bemisia tabaci Q-biotype nymphs.

BACKGROUND: Lecanicillium lecanii is an entomopathogenic fungi, which was isolated from insects suffering from disease. Now, it is an effective bio-control resource that can control agricultural pests such as whitefly and aphids. There are many studies on the control of various agricultural pests by L. lecanii, but no report on its control of Bemisia tabaci biotype-Q exists. In this work, we studied the susceptibility of B. tabaci Q-biotype (from Ningxia, China) to L. lecanii JMC-01 in terms of nymph mortality and the changes in detoxifying protective enzymes activities. METHODS: B. tabaci nymphs were exposed to L. lecanii JMC-01 conidia by immersion with the host culture. Mortality was assessed daily for all nymph stages. The detoxifying and protective enzyme activity changes, weight changes, and fat, and water contents of the nymphs were determined spectrophotometrically. RESULTS: All instars of B. tabaci died after being infested with 1 × 108 conidia/mL. The 2nd-instar nymphs were the most susceptible, followed by the 3rd-instar nymphs. The corrected cumulative mortality of the 2nd- and 3rd-instar nymphs was 82.22% and 75.55%, respectively. The levels of detoxifying and protective enzymes initially increased and then decreased. The highest activities of carboxylesterase, acetylcholinesterase, peroxidase, and catalase occurred on the 3rd day, reaching 10.5, 0.32, 20, and 6.3 U/mg prot, respectively. These levels were 2.2-, 4.3-, 2.4-, and 1.4-fold the control levels, respectively. The highest activities of glutathione-S transferase and superoxide dismutase on the 2nd day were, respectively, 64 and 43.5 U/mg prot. These levels were, respectively, 2.7 and 1.1-fold that of the control level. The water and fat content in the infected B. tabaci nymphs decreased and differed significantly from the control levels. The weight increased continuously in the first 24 h, decreasing thereafter. At 72 h, the infestation level was about 0.78-fold that of the control level. CONCLUSIONS: The studied L. lecanii JMC-01 strain is pathogenic to the B. tabaci Q-biotype. This strain interferes with the normal functioning of detoxifying and protective enzymes, and is also involved in the disruption of normal physiological metabolism in B. tabaci.

[Effects of spraying paclobutrazol at different stages on physiological characteristics, yield and quality of peanut]. / 不同时期喷施多效唑对花生生理特性、产量和品质的影响.

To explore the optimum stage of spraying with paclobutrazol (PBZ) for different peanut cultivars under high yield condition, we investigated the effects of spraying PBZ at different stages on chlorophyll content, root activity, protective enzymes, nitrogen and carbon metabolism enzymes of leaves, pod yield and kernel quality of peanut, with Huayu 20 and Huayu 25 as materials. The results showed that spraying PBZ at different stages increased root activity, chlorophyll content, SOD, POD, CAT, SS, SPS, PEPC activities and decreased the MDA content, NR, GS, GDH and GOGAT activities for pod setting stage of two cultivars. These results suggested that the effects would be more obvious at earlier spray time. For HY25, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 25 cm. For HY20, spraying PBZ when the main stem height was 25 cm decreased the activities of protective enzymes. Earlier spraying time to HY20 would lead to early senescence, lower chlorophyll content, root activity and carbon metabolism enzyme activity. For HY20, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 30 cm. Our results indicated that PBZ treatments at the optimum stage could improve pod yield and economic coefficient of both cultivars and enhance the fat content and the relative content of oleic acid and the O/L. Under high yield condition, the optimum stage of spraying PBZ was 25 cm height of the main stem for HY25 and 30 cm for HY20.

[Effects of soil water content on growth and accumulation of active ingredients of Notopterygium incisum].

To investigate the adaptive mechanism of Notopterygium incisum to water changes, one-year-old seedlings were used as test materials. The characteristics of growth, physiology, and active ingredients of N. incisum were studied at different soil water content by pot experiments. The result showed that: ①The water content at 100% field capacity is conducive to the growth and accumulation of biomass of N. incisum. The leaf length, petiole length, petiole diameter, root diameter, root length and biomass of underground dry of N. incisum were all significantly increased at the 100% field capacity, and they slightly declined at 70% field capacity. 20% field capacity could not provide the necessary water to growth of N. incisum, all N. incisum withered and died. ②With the extension of moisture treatment time, the relative content of chlorophyll (SPAD) in leaves and the activity of peroxidase (POD) in rhizome showed a trend of increasing firstly, decreasing then; the tendency of activity of superoxide dismutase (SOD) in rhizome increased; the content of malondialdehyde (MDA) in rhizome decreased firstly and increased then;. For the late test, the SPAD value, the activity of POD and SOD in N. incisum at the 40% field capacity were lower than 70% field capacity and 100 field capacity, while the content of MDA in rhizome were higher than 70% field capacity and 100% field capacity. ③ At 70% field capacity, the active ingredients accumulated most in the N. incisum. At the 70% field capacity, the notopterol and isoimperatorinwerehigher than100 field capacity and 40 field capacity. In summary, the soil water content at 70%-100% field capacity would contribute to the growth and accumulation of active ingredients of N. incisum.

Extraction, purification and elicitor activities of polysaccharides from Chrysanthemum indicum.

Polysaccharides isolated from Chrysanthemum indicum were studied for their pathogen-derived resistance against Sclerotium rolfsii sacc in Atractylodis maceocephalae koidz. The total sugar content and monosaccharide analysis were determined by phenol-sulfuric acid method and gas chromatography, and infrared spectroscopy performed for simple structure information. The activities of CAT and POD as protective enzymes in A. maceocephalae leaves were evaluated. The purified polysaccharides exhibited strong CAT and POD activities in inoculated with S. rolfsii in A. macrocephala leaves, attained the maximum value 568.3 Ug(-1)min(-1) and 604.4 Ug(-1)min(-1)respectively. Whereas, when compared with the control plants, 20mg/ml purified polysaccharides exhibited the strongest CAT and POD activities. Notably, the treatments of A. macepcephalae seedlings with C. indicum polysaccharides (CIP) decreased disease index development caused by S. rolfsii. The disease index after 10 days was significantly reduced when the seedlings treated with 20mg/ml CIP, 4.41 compared to the control plants 32.00. Given together, these results indicated that purified polysaccharides derived from C. indicum may be useful as a natural inducer.