Antioxidant Enzyme Responses Induced by Whiteflies in Tobacco Plants in Defense against Aphids: Catalase May Play a Dominant Role

Insights into roles of biochar on migration and accumulation of cadmium in Spartina alterniflora Loisel. -sediment systems and their microbial effects

It is widely recognized that remediating cadmium (Cd)-contaminated sediments using biochar (BC) can significantly influence plant growth and development. However, the efficiency of such remediation often diminishes in field trials compared to greenhouse experiments, likely due to limited comprehension of the BC addition on the plant-sediment-microbe interaction. In this study, a 56-day pot experiment demonstrated that BC application offered (i) enhanced plant root length and biomass, (ii) increased proline content, (iii) improved photosynthetic capacity (e.g., total chlorophyll content), and (iv) mitigated oxidative stress (e.g., decreased the peroxidase (POD) and (CAT) activity, and increased superoxide dismutase (SOD) activity). The increased SOD allowed better scavenging of reactive oxygen species (ROS) in leaves (the primary site of ROS generation), thereby alleviating leaf growth retardation. Notably, the translocation factor of Cd significantly reduced to 0.0034 in BC-amended sediments, under high-Cd toxicity. Qualitative and quantitative analysis identified that BC facilitated the Cd binding ability on the wall of the root cells (up to 85.67 ± 0.88 %) by increasing the adsorption capacity of matrix polysaccharides. Furthermore, the bioavailable Cd proportion in sediments was markedly reduced after BC addition. BC also increased the relative abundances of bacteria, such as Desulfuromonadia and Alteromonadaleswhich were involved in Cd immobilization, and enhanced microbial adaptability to Cd-stress by boosting genetic and environmental information processing functions. The mechanisms on how BC reduced the bioavailable Cd in sediment was dependent on both BC and root presence. These findings demonstrated that BC application is an effective strategy for remediating Cd-contaminated coastal wetlands, offering significant benefits for environmental health and human well-being.

Puccinia triticina and Salicylic Acid Stimulate Resistance Responses in Triticum aestivum Against Diuraphis noxia Infestation

Wheat plants encounter both biotic and abiotic pressure in their surroundings. Among the biotic stress factors, the Russian wheat aphid (RWA: Diuraphis noxia Kurdjumov) decreases grain yield and quality. The current RWA control strategies, including resistance breeding and the application of aphicides, are outpaced and potentially environmentally harmful. Alternatively, priming can stimulate defence responses to RWA infestation. This study investigated the priming potential of two priming agents, avirulent Puccinia triticina (Pt) isolates and salicylic acid (SA), against RWA infestation. The priming effect of Pt isolates and SA in reducing RWA-induced leaf damage and increased antioxidant activities is an indication of defence responses. Selected South African wheat cultivars and Lesotho landraces, grown under greenhouse conditions, were inoculated with Pt isolates (UVPt13: avirulent, UVPt26: virulent) and treated with SA at the seedling or booting stages. The leaf damage rating score was used for phenotyping. The antioxidant-mediated defence responses were evaluated in three selected cultivars for further priming investigation. Our results revealed that the priming agents significantly reduced the leaf damage in most cultivars at both growth stages, and UVPt13 and SA priming significantly (p ≤ 0.05) increased superoxide dismutase, peroxidase, and ascorbate peroxidase activities. However, catalase activity exhibited a more pronounced decline in plants treated with the UVPt13 isolate. The Pt isolate priming was more efficient than the SA application. However, it is crucial to investigate the potential of effectors from the avirulent Pt isolate to prime wheat plants for resistance against RWA infestation. This could contribute to developing strategies to enhance crop protection and relieve pest pressure in wheat production.

Changes in MicroRNAs expression mediate molecular mechanism underlying the effect of MeJA on the biosynthesis of podophyllotoxin in Linum album cells

Podophyllotoxin (PTOX), produced by Linum album, is a monolignol that participates in plant defense strategies. Our previous study established that methyl jasmonate (MeJA) significantly stimulates PTOX production in L. album cells. However; the mechanisms by which MeJA regulates PTOX biosynthesis are uncovered. In the present study, we demonstrated that MeJA induces a time-dependent hydrogen peroxide (H2O2) and salicylic acid (SA) accumulation but reduces nitric oxide (NO) generation in L. album cells. PTOX biosynthetic genes such as PAL, CCR, CAD, and PLR were upregulated in response to MeJA exposure. Furthermore, the results of RT-qPCR revealed a positive correlation between the expression of PTOX biosynthetic genes and MeJA-induced upregulation of four miRNAs such as miR156, miR159, miR172, and miR396 at 12 h. Generally, this study revealed that MeJA mediates PTOX biosynthesis in L. album cells by inducing H2O2 and SA formation, which can probably upregulate the expression level of some miRNAs and biosynthetic genes in a redox balance-dependent manner.

Biochemical responses of Echinochloa polystachya inoculated with a Trichoderma consortium during the removal of a pyrethroid-based pesticide

The biochemical response of plants exposed to pesticides and inoculated with microorganisms is of great importance to explore cleaning up strategies for contaminated sites with pyrethroid-based pesticides. We evaluated the effects of a Trichoderma consortium on the biochemical responses of Echinochloa polystachya plants during the removal of a pyrethroid-based pesticide. Plants were inoculated or not with the Trichoderma consortium and exposed to commercial pesticide H24®, based on pyrethroids. Pesticide application resulted in significant reduction in root protein content (58%), but enhanced content of malondialdehyde (MDA) in shoots, superoxide dismutase (SOD) activity in shoots and roots, and catalase (CAT) activity in roots. Inoculation of Trichoderma consortium in E. polystachya exposed to the pesticide resulted in increased protein content in roots and MDA content in shoots (2-fold). Trichoderma consortium improved protein content and SOD activity (140-fold) in plants. Fungal inoculation increased the removal (97.9%) of the pesticide in comparison to the sole effect of plants (33.9%). Results allow further understanding about the responses of the interaction between plants and root-associated fungi to improving the assisted-phytoremediation of solid matrices contaminated with organic pesticides.

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.

Biochemical Defense Responses in Red Rice Genotypes Possessing Differential Resistance to Brown Planthopper, Nilaparvata lugens (Stål)

The brown planthopper [Nilaparvata lugens (Stål.)] is one of the most destructive insect pests in all the rice-growing regions of the world. The pest is complicated to manage through the blanket application of chemical pesticides. The development of stable, durable N. lugens-resistant rice varieties is the most economical and efficient strategy to manage the pest. Landraces of red rice genotypes possess numerous nutritional and stress-resistant properties, though an exclusive study on the same is yet to be carried out. In the present study, we evaluated 28 red rice genotypes, along with two resistance checks and one susceptibility check, for their resistance to N. lugens. These promising lines revealed differential responses in the defense mechanism against the pest. The resistant accessions showed a greater accumulation of phenols, peroxidase, polyphenol oxidase, catalase, and superoxide dismutase under N. lugens-stressed conditions. However, the concentration of soluble proteins was substantially decreased in all the test genotypes. The concentration of crude silica was at maximum in highly resistant genotypes. Six red rice genotypes, namely Mata Meher, Manipuri Black, Hermonona, Sonahanan, Bavdi, and Bacharya Khuta fall under the highly resistant category, and can be utilized as valuable sources of resistance in breeding programs.

Biochemical probing of phloem sap defensive traits in Brassica juncea-B. fruticulosa introgression lines following Lipaphis erysimi infestation

The lack of resistance to Lipaphis erysimi in cultivated Brassicas makes caused this pest highly devastating resulting in significant loss of rapeseed-mustard productivity in India. B. fruticulosa, a wild crucifer is known as an excellent source of resistance to L. erysimi. Therefore, we planned to assess defense associated biochemical alterations and molecular components of B. juncea-B. fruticulosa ILs to mustard aphid. Phenotypic assessment of ILs on the basis of aphid population per plant (APP) categorized genotypes into resistant (7.15-18.50 APP), moderately susceptible (42.29-53.33 APP) and susceptible (70.00-77.07 APP) genotypes. Mustard aphid infested minimally B. fruticulosa (0.80 APP) among tested genotypes. The maximum increase in catalase (CAT) activity was determined in B. fruticulosa and resistant ILs after 48 h (2.03 and 1.76-fold, respectively) and one week (2.98 and 1.79-fold, respectively) of mustard aphid infestation. The strong induction of CAT2 transcripts (19.25-fold) and CAT activity (5.88-fold) along with low aphid count in resistant IL, Ad4-64 (13.85 APP) suggested the pivotal role of CAT in resistance to mustard aphid. Guaiacol peroxidase (GPX) was significantly decreased following pest infestation at both infestation stages. The ascorbate content was highest in resistant IL, ADV-6RD (2.14-fold) after one week of aphid infestation. H2O2 content rapidly increased in B. juncea-B. fruticulosa derived lines after 48 h of aphid infestation. The negative and significant association between APP and CAT (- 0.56** and - 0.48*, respectively), glutathione (- 0.43* and - 0.40*, respectively), H2O2 (- 0.57** and - 0.43*, respectively) at both 48 h and one week infestation stages signified their role in deterring mustard aphid infestation. The positive and significant association between total sugars (0.33* at 7 DPI), reducing sugars (0.33* at 7 DPI), sucrose (0.36** at 48 h) and APP indicated that higher the sugars content, higher will be mustard aphid infestation in B. juncea derived ILs. The information being generated and key candidates (CAT2, ascorbate and H2O2) being identified may help in effective deployment of B. fruticulosa resistance in mustard breeding.

Effects of drought stress and plant cultivar type on demographic characteristics of the rose-grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae)

Drought is a substantial threat to cereal production under global climatic change scenarios, albeit its aftermath on arthropod pests is yet contentious. To address this issue, demographic characteristics of Metopolophium dirhodum (Walker, 1849) (Hemiptera: Aphididae) were studied on one drought-susceptible wheat cultivar and one drought-tolerant wheat cultivar under different water treatments. Some physiological and biochemical features of wheat cultivars including leaf soluble sugar and proline contents and antioxidant enzymes activities were also investigated. Significant differences occurred in the developmental period, survival, and fecundity of M. dirhodum between wheat cultivars under various water treatments. The impact of intermediate and severe water stress on M. dirhodum was neutral and negative for the tolerant cultivar and negative for the water-susceptible cultivar, respectively. Under severe water stress, on both wheat cultivars, the aphids had low net reproductive rates and finite and intrinsic rates of increase in comparison with those reared on unstressed plants. In total, drought resulted in lower growth of population and reduced survival of aphids. Hence, in the context of projected climatic changes, acute water deficiency could probably result in reducing the abundance and menace of outburst of M. dirhodum. However, it should be noted that the potential likelihood of M. dirhodum eruptions can be drastically affected by the degree of drought intensity and host plant cultivar.

Exogenous melatonin induces phenolic compounds production in Linum album cells by altering nitric oxide and salicylic acid

Melatonin is a pleiotropic molecule that can influence various aspects of plant performance. Recent studies have exhibited that it mediates plant defensive responses, probably through managing redox homeostasis. We tried to track the regulatory effects of melatonin on the antioxidant machinery of Linum album cell culture. To this, different concentrations of melatonin were applied, and the oxidative status of cells was investigated by measuring the levels of oxidative molecules and antioxidant agents. The results showed that H₂O₂ content did not change at the low melatonin levels, while it increased at the high concentrations. It can be correlated with the low melatonin dosages capacity to remove excessive amounts of H₂O₂, while the high melatonin dosages exhibit toxicity effects. In contrast, the NO enhancement occurred at 50 μM melatonin, proposing its role in triggering melatonin-induced defensive responses. The MDA results stated that NO led to oxidative stress in melatonin-treated cells at 50 μM melatonin. Antioxidant enzyme POD was activated by melatonin treatment, while SOD enzyme behaved reversely which can explain the changes in the H₂O₂ level. In addition, the analysis of the phenolics profile showed that the contents of phenolic acids, flavonoids, and lignans enhanced following an increase in PAL enzyme activity. The increased level of phenolic hormone SA can indicate that melatonin affects the defensive responses in L. album cells through a SA-dependent pathway. In general, it seems that melatonin, by modulating NO and SA levels, can induce the activity of antioxidant enzymes and the production of phenolics, especially lignans, in L. album cells.

Different responses of two maize cultivars to Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae infestation provide insights into their differences in resistance

Spodoptera frugiperda (Lepidoptera: Noctuidae), a pest with an amazing appetite, damages many crops and causes great losses, especially maize. Understanding the differences in different maize cultivars' responses to S. frugiperda infestation is very important for revealing the mechanisms involved in the resistance of maize plants to S. frugiperda. In this study, a comparative analysis of two maize cultivars, the common cultivar 'ZD958' and the sweet cultivar 'JG218', was used to investigate their physico-biochemical responses to S. frugiperda infestation by a pot experiment. The results showed that the enzymatic and non-enzymatic defense responses of maize seedlings were rapidly induced by S. frugiperda. Frist, the hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents of infested maize leaves were significantly increased and then decreased to the level of the control. Furthermore, compared with the control leaves, the puncture force values and the total phenolics, total flavonoids, and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one contents of infested leaves were significantly increased within a certain time. The superoxide dismutase and peroxidase activities of infested leaves were significantly increased in a certain period of time, while the catalase activities decreased significantly and then increased to the control level. The jasmonic acid (JA) levels of infested leaves were significantly improved, whereas the salicylic acid and abscisic acid levels changed less. Signaling genes associated with phytohormones and defensive substances including PAL4, CHS6, BX12, LOX1, and NCED9 were significantly induced at certain time points, especially LOX1. Most of these parameters changed greater in JG218 than in ZD958. Moreover, the larvae bioassay showed that S. frugiperda larvae weighed more on JG218 leaves than those on ZD958 leaves. These results suggested that JG218 was more susceptible to S. frugiperda than ZD958. Our findings will make it easier to develop strategies for controlling S. frugiperda for sustainable maize production and breeding of new maize cultivars with increased resistance to herbivores.

Arbuscular Mycorrhizal Fungus Alters Alfalfa (Medicago sativa) Defense Enzyme Activities and Volatile Organic Compound Contents in Response to Pea Aphid (Acyrthosiphon pisum) Infestation

Pea aphid (Acyrthosiphon pisum) infestation leads to withering, reduced yield, and lower quality of the host plant. Arbuscular mycorrhizal (AM) fungi have been found to enhance their host plants’ nutrient uptake, growth, and resistance to biotic stresses, including pathogen infection and insect pest infestation. Therefore, we evaluated the effects of AM fungus Rhizophagus intraradices on alfalfa defense responses to pea aphid infestation. Aphid infestation did not affect the colonization of AM fungus. The inoculation of AM fungus, on average, enhanced alfalfa catalase and the contents of salicylic acid and trypsin inhibitor by 101, 9.05, and 7.89% compared with non-mycorrhizal alfalfa, respectively. In addition, polyphenol oxidase activities significantly increased by six-fold after aphid infestation in mycorrhizal alfalfa. Moreover, the fungus significantly (p < 0.05) improved alfalfa shoot N content, net photosynthetic and transpiration rates, and shoot dry weight in aphid infected treatment. The aphid infestation changed the total volatile organic compounds (VOCs) in alfalfa, while AM fungus enhanced the contents of methyl salicylate (MeSA). The co-expression network analysis of differentially expressed genes (DEGs) and differentially expressed VOCs analysis showed that three DEGs, namely MS.gene23894, MS.gene003889, and MS.gene012415, positively correlated with MeSA both in aphid and AM fungus groups. In conclusion, AM fungus increased alfalfa’s growth, defense enzyme activities, hormones, and VOCs content and up-regulated VOC-related genes to enhance the alfalfa’s resistance following aphid infestation.

Assessment of Parectopa robiniella Clemens (Lepidoptera: Gracillariidae) Effect on Biochemical Parameters of Robinia pseudoacacia Under Conditions of an Industrial City in Steppe Ukraine

Antioxidant enzymatic activity and soluble protein content in Robinia pseudoacacia L. (black locust), invasive tree in Europe, plants were determined under feeding conditions of the caterpillars of Parectopa robiniella Clemens, 1863, invasive miner in Europe, in trees of three (I, II, III) age groups (5–10, 15–25, and 40 years). Biochemical analysis data showed significant differences between reference and experimental leaf samples in different urban ecosystems. There was no association between changes in catalase and peroxidase activity and protein content under the influence of leaf blotch miners depending on the tree age. Significant variability of proteins under P. robiniella influence was noted; the highest of its values were recorded in the leaves of ІІІ-aged trees. In most plantings (and especially in trees of age group III), an increase (1.2 to 2.7 times) in GPx activity or the absence of its changes was registered both in the ecologically favorable zone and in the locations affected by emissions from road transport and industrial enterprises. Plants of age groups I and II in the emission areas of metallurgical, pipe-rolling, and chemical industries experienced a significant decrease in GPx activity (by 20.2–44.6%) in the leaves damaged by the phytophage. In most of the plantings studied, catalase showed an increase/stability of its activity in all age groups of trees under condition of pest attack. The highest increase in САТ activity (2.1 times) was recorded in young R. pseudoacacia plants in an ecologically favorable area of the city.

Prospective of mycorrhiza and Beauvaria bassiana silica nanoparticles on Gossypium hirsutum L. plants as biocontrol agent against cotton leafworm, Spodoptera littoralis

BACKGROUND

Plant-herbivorous insects are a severe danger to the world's agricultural production of various crops. Insecticides used indiscriminately resulted in habitat destruction due to their high toxicity, as well as disease resistance. In this respect, the development of a sustainable approach to supreme crop production with the least damage is a crucially prerequisite. As a result, the current study was carried out to understand the potential effect of arbuscular mycorrhizal (AM) fungi along with Beauvaria bassiana silica nanoparticles (Si NPs) as a new approach to increase cotton (Gossypium hirsutum L. Merr.) defense against an insect herbivore, Spodoptera littoralis. AM and non-AM cotton plants were infested with S. littoralis and then sprayed with a biopesticide [B. bassiana Si NPs] or a chemical insecticide (Chlorpyrifos).

RESULTS

The gas chromatography-mass spectrometry (GC-MS) analysis of B. bassiana Si NPs fungal extract showed that the major constituents identified were Oleyl alcohol, trifluoroacetate, 11-Dodecen-1-AL and 13-Octadecenal, (Z)-(CAS). Besides, results revealed a highly significant decrease in growth parameters in S. littoralis infested plants, however, with AM fungal inoculation a substantial improvement in growth traits and biochemical parameters such as protein and carbohydrates contents was observed. In addition, stimulation in proline and antioxidant enzymes activity and a decrease in malondialdehyde content were observed after AM inoculation.

CONCLUSION

AM fungi mitigate the harmful effects of herbivorous insects by strengthening the cotton plant's health via enhancing both morphological and biochemical traits that can partially or completely replace the application of chemical insecticides.

Change in the Physiological and Biochemical Aspects of Tomato Caused by Infestation by Cryptic Species of Bemisia tabaci MED and MEAM1

Infestation by Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) causes damage to tomatoes with production losses of up to 100%, affecting the physiological and biochemical aspects of host plants. The objective of this study was to analyze the influence of infestation of cryptic species of B. tabaci MED and MEAM1 on the physiological and biochemical aspects of tomato. Tomato plants 'Santa Adélia Super' infested with B. tabaci (MED and MEAM1), and non-infested plants were evaluated for differences in gas exchange, chlorophyll - a fluorescence of photosystem II (PSII), and biochemical factors (total phenols, total flavonoids, superoxide dismutase-SOD, peroxidase-POD, and polyphenol oxidase-PPO). Plants infested with B. tabaci MED showed low rates of CO2 assimilation and stomatal conductance of 55% and 52%, respectively. The instantaneous carboxylation efficiency was reduced by 40% in MED and by 60% in MEAM1 compared to the control. Regarding biochemical aspects, plants infested by MED cryptic species showed high activity of POD and PPO enzymes and total phenol content during the second and third instars when compared to control plants. Our results indicate that B. tabaci MED infestation in tomato plants had a greater influence than B. tabaci MEAM1 infestation on physiological parameters (CO2 assimilation rate (A), stomatal conductance (gs), and apparent carboxylation efficiency (A/Ci)) and caused increased activity of POD and PPO enzymes, indicating plant resistance to attack. In contrast, B. tabaci MEAM1 caused a reduction in POD enzyme activity, favoring offspring performance.

Evidence for rice tolerance to Tibraca limbativentris (Hemiptera: Pentatomidae)

BACKGROUND

The rice stalk stink bug Tibraca limbativentris (Hemiptera: Pentatomidae) is one of the most important rice pests in Brazil. The search for cultivars that tolerate insect injury is necessary to complement other less aggressive methods of pest suppression. The combination of integrated pest management tactics will reduce insecticide applications and improve the safety of food production. Here, we tested the tolerance response of Xingu, Canela de Ferro and Primavera rice genotypes in glasshouse experiments. In addition, we measured tolerance expressed in a variety of physiological responses, including gas exchange rates, leaf chlorophyll content and reactive oxygen species (ROS) detoxification.

RESULTS

The results showed that the tolerance of the Primavera genotype to rice stalk stink bug damage was higher, due to (a) a lower reduction of photosynthetic activity, (41% reduction only 96 h after infestation) compared to Xingu and Canela de Ferro (56 and 65% reduction at 24 and 48 h after infestation, respectively); (b) the capacity to maintain the chlorophyll content after infestation, while Xingu and Canela de Ferro reduced their chlorophyll content to 20% and 25% at 72 and 48 h after infestation, respectively; (c) the antioxidative defense system being activated in the first 12 h after infestation, in which superoxide dismutase (SOD) showed an increase of 61% in its activity, and (d) the maintenance of its grain yield, number of panicles per plant, number of filled grains, and spikelets sterility.

CONCLUSION

Rice genotypes tolerant to herbivory can be identified by measuring the effect of injury and the plant's physiological response by evaluating attributes such as grain yield and its components, gas exchange, chlorophyll content and ROS detoxification. Therefore, the use of rice genotypes tolerant to stalk stink bugs as a component of integrated pest management has the potential to reduce upland rice yield loss.

Elevated production of reactive oxygen species is related to host plant resistance to sugarcane aphid in sorghum

Sugarcane aphid (Melanaphis sacchari) is a phloem-feeding insect that severely affects the growth and productivity of sorghum and other related crops. While a growing body of knowledge is accumulating regarding plant, and insect interactions, the role of reactive oxygen species (ROS) against aphid infestation in sorghum has not been established yet. Here, the involvement of H2O2 and ROS detoxification enzymes in host plant resistance to sugarcane aphid in sorghum was demonstrated. The H2O2 accumulation and expression patterns of selected ROS scavenging enzymes including ascorbate peroxidase (APX), glutathione S transferase (GST), superoxide dismutase (SOD), and catalase (CAT) in response to sugarcane aphid infestation at 3, 6, 9, and 12 days post infestation (dpi) in resistant (Tx2783) and susceptible (Tx7000) sorghum genotypes were assessed, respectively. A significant increase in H2O2 accumulation was observed in resistant genotypes at all time points studied as compared to susceptible plants. Furthermore, gene expression analysis revealed that in responding to attack by sugarcane aphid, antioxidant genes were induced in both genotypes, but much stronger in the resistant line. Furthermore, aphid survival and fecundity were significantly inhibited in resistant plants compared to susceptible plants. Taken together, our results suggest that the elevated accumulation of H2O2 and the strong upregulation of the antioxidant genes in sorghum may have contributed to host plant resistance in Tx2783 against sugarcane aphid but the weak expression of those antioxidant genes in Tx7000 resulted in the failure of attempting defense against sugarcane aphid. This report also provides the experimental evidence for the role of ROS involvement in the early defensive response to an attack by sugarcane aphid in sorghum.

Effect of food plants on Spodoptera litura (Lepidoptera: Noctuidae) larvae immune and antioxidant properties in response to Bacillus thuringiensis infection

The larvae of Spodoptera litura (Fabricius) were reared on five host plants, Brassica oleracea, Nicotiana tabacum, Ricinus communis, Gossypium hirsutum, and Arachis hypogaea. The larvae were immunized with Bacillus thuringiensis to observe the immune response. The results of total and differential hemocyte count were increased in B. oleracea, N. tabacum, and R. communis fed S. litura larval hemolymph. Similar results were observed in the parameter of nodulation, melanization, and phenoloxidase. Total protein was higher in R. communis fed larvae. Antioxidant levels like Catalase (CAT), Superoxide dismutase (SOD), Glutathione S- transferase (GST), Peroxidase (POX), Lipid peroxidase (LPO), and Esterase (EST) was found in moreover all plant-feeding insect. High CAT activity was observed 2-6 h in R. communis, G. hirsutum, and A. hypogaea fed S. litura larval midgut and fatbody samples. Increased SOD activity in both midgut and fatbody at 2-12 h of B. oleracea, G. hirsutum, and A. hypogaea fed. GST activity was increased initially 2-6 h in G. hirsutum and A. hypogaea. Increased POX activity was observed initially in all treated groups. Highest LPO observed at 6 h in N. tabacum in both midgut and fatbody. Whereas increased EST activity was observed in N. tabacum and B. oleracea. The results of the present study shows that nature of food influence the immunity against Bt infection. This information can be very useful for incorporating biological control program for insect pest.

Sodium alginate potentiates antioxidant defense and PR proteins against early blight disease caused by Alternaria solani in Solanum lycopersicum Linn

The use of biopolymers as elicitors in controlling plant diseases is gaining momentum world-wide due to their eco-friendly and non-toxic nature. In the present study, we have used an algal biopolymer (sodium alginate) and tested its applicability as an elicitor in inducing resistance factors against Alternaria solani, which causes early blight disease in Solanum lycopersicum (tomato plant). We have pre-treated tomato plants with different concentrations of sodium alginate (0.2%, 0.4%, and 0.6%) before A. solani infection. We found that sodium alginate has effectively controlled the growth of A. solani. In addition, a significant increase in the expression levels of SOD was observed in response to pathogen infection. The increased protease inhibitors activity further suggest that sodium alginate restrict the development of A. solani infection symptoms in tomato leaves. This corroborates well with the cell death analysis wherein increased sodium alginate pre-treatment results in decreased cell death. Also, the expression profile analyses reveal the induction of genes only in sodium alginate-pretreated tomato leaves, which are implicated in plant defense mechanism. Taken together, our results suggest that sodium alginate can be used as an elicitor to induce resistance against A. solani in tomato plants.

Proteomic Analysis of MeJa-Induced Defense Responses in Rice against Wounding

The role of jasmonates in defense priming has been widely recognized. Priming is a physiological process by which a plant exposed to low doses of biotic or abiotic elicitors activates faster and/or stronger defense responses when subsequently challenged by a stress. In this work, we investigated the impact of MeJA-induced defense responses to mechanical wounding in rice (Oryza sativa). The proteome reprogramming of plants treated with MeJA, wounding or MeJA+wounding has been in-depth analyzed by using a combination of high throughput profiling techniques and bioinformatics tools. Gene Ontology analysis identified protein classes as defense/immunity proteins, hydrolases and oxidoreductases differentially enriched by the three treatments, although with different amplitude. Remarkably, proteins involved in photosynthesis or oxidative stress were significantly affected upon wounding in MeJA-primed plants. Although these identified proteins had been previously shown to play a role in defense responses, our study revealed that they are specifically associated with MeJA-priming. Additionally, we also showed that at the phenotypic level MeJA protects plants from oxidative stress and photosynthetic damage induced by wounding. Taken together, our results add novel insight into the molecular actors and physiological mechanisms orchestrated by MeJA in enhancing rice plants defenses after wounding.