Cercospora Arachidicola Research Articles

Design, synthesis and fungicidal evaluation of novel psoralen derivatives containing sulfonohydrazide or acylthiourea moiety.

To search a novel lead structure for antiphytopathogenic fungus agent, a series of novel psoralen derivatives possessing sulfonohydrazide or acylthiourea structure were designed and synthesized, and their fungicidal activity against seven phytopathogens was evaluated. Their structures were confirmed by melting points, 1H NMR, 13C NMR and HRMS, and the typical crystal structure was determined by X-ray diffraction for validation. Preliminary fungicidal activity showed that some of the title compounds exhibited certain-to-high fungicidal activity. Compound I-13 exhibited good fungicidal activity against Botrytis cinerea, Cercospora arachidicola and Physalospora piricola with EC50 values of 12.49, 13.22 and 12.12 μg/mL, respectively. Compounds II-9 and II-15 showed over 90% inhibition against B. cinerea at 50 μg/mL in vitro. In particular, II-9 exhibited significant higher fungicidal activity with a lower EC50 value of 9.09 μg/mL than the positive control YZK-C22 (13.41 μg/mL). Our studies found that sulfonohydrazide or acylthiourea-containing psoralen derivatives were promising fungicide leads deserve for further study.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11030-022-10402-y.

Occurrence of early leaf spot disease (Cercospora arachidicola Hori.) of groundnut (Arachis hypogaea L.) in Bikaner region of Rajasthan

Groundnut (Arachis hypogaea L.) is the major oil seed legume crop in the world. The production and productivity of groundnut is highly affected by collar rot, early leaf spot, Late leaf spot, rust and stem rot diseases. Among the foliar fungal diseases, early leaf spot (ELS) caused by Cercospora arachidicola Hori is one of the most destructive disease in Rajasthan. The early leaf spot infected leaves of groundnut was found to produce typical symptoms, such as presence of light brown to black circular to irregular lesions with chlorotic hallow on the upper surface of the leaves. A proper investigation needs a perfect scrutiny. So, the survey was carried out during Kharif-2019 in the three major groundnut growing tehsils (Nokha, Lunkaransar and Shri Dungargarh) of Bikaner district revealed that none of the locations were free from the disease. However, maximum disease intensity of early leaf spot was observed in Shri Dungargarh tehsil (25.87%) followed by Lunkaransar tehsil (19.32%) at the crop age 45-60 days after sowing.

Novel Dioxolane Ring Compounds for the Management of Phytopathogen Diseases as Ergosterol Biosynthesis Inhibitors: Synthesis, Biological Activities, and Molecular Docking.

Thirty novel dioxolane ring compounds were designed and synthesized. Their chemical structures were confirmed by 1H NMR, HRMS, and single crystal X-ray diffraction analysis. Bioassays indicated that these dioxolane ring derivatives exhibited excellent fungicidal activity against Rhizoctonia solani, Pyricularia oryae, Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium oxysporum, Physalospora piricola, Cercospora arachidicola and herbicidal activity against lettuce (Lactuca sativa), bentgrass (Agrostis stolonifera), and duckweed (Lemna pausicostata). Among these compounds, 1-((2-(4-chlorophenyl)-5-methyl-1,3-dioxan-2-yl)methyl)-1H-1,2,4-triazole (D17), 1-(((4R)-2-(4-chlorophenyl)-4-methyl-1,3-dioxolan-2-yl)methyl)-1H-1,2,4-triazole (D20), 1-((5-methyl-2-(4-(trifluoromethyl)phenyl)-1,3-dioxan-2-yl)methyl)-1H-1,2,4-triazole (D22), and 1-((2-(4-fluorophenyl)-1,3-dioxolan-2-yl)methyl)-1H-1,2,4-triazole (D26) had broad spectrum fungicidal and herbicidal activity. The IC50 values against duckweed were 20.5 ± 9.0, 14.2 ± 6.7, 24.0 ± 11.0, 8.7 ± 3.5, and 8.0 ± 3.1 μM for D17, D20, D22, and D26 and the positive control difenoconazole, respectively. The EC50 values were 7.31 ± 0.67, 9.74 ± 0.83, 17.32 ± 1.23, 11.96 ± 0.98, and 8.93 ± 0.91 mg/L for D17, D20, D22, and D26 and the positive control difenoconazole against the plant pathogen R. solani, respectively. Germination experiments with Arabidopsis seeds indicated that the target of these dioxolane ring compounds in plants is brassinosteroid biosynthesis. Molecular simulation docking results of compound D26 and difenoconazole with fungal CYP51 P450 confirmed that they both inhibit this enzyme involved in ergosterol biosynthesis. The structure-activity relationships (SAR) are discussed by substituent effect, molecular docking, and density functional theory analysis, which provided useful information for designing more active compounds.

Effect of Pseudomonas fluorescens and Botanicals against Tikka Leaf Spot Disease (Cercospora arachidicola, Cercospora personatum) of Groundnut (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is an important oilseed crop in India. It is susceptible from many diseases, tikka disease is one of them. Tikka disease is due to Cercospora arachidicola, Cercospora personatum causes much damage to production and pod quality. A survey was conducted during Rabi 2020-21 to know the incidence of Tikka disease of groundnut in farmer’s fields in Visakhapatnam district of Andhra Pradesh. Five villages were selected in the district and in each village two fields were surveyed. The disease incidence ranged from 29 to 50 per cent irrespective of location surveyed. The disease incidence was least in Taruva village (29%) and highest in Alamanda village (50%) during the month of January to March 2021. To manage the disease an investigation was carried out in farmer’s field during Rabi 2020-21 in Taruva village, Devarapalle mandal, Visakhapatnam district of Andhra Pradesh to evaluate the efficacy of Bio-agent viz.., Pseudomonas fluorescens (S.T), Botanicals viz.., Extract and oil sprays of Neem, Eucalyptus, Clove. Among the treatments the plant height (cm), No. of branches, Root length and Pods per plant at 90 DAS was significantly increased in T3 – S.T with Pseudomonas fluorescens + neem oil (F.S) (42.8 cm), (6.2), (9.72), (28.51) respectively. The Disease incidence (%) at 90 DAS was significantly decreased in treatment T3 - S.T with Pseudomonas fluorescens + neem oil (F.S) (15.5%). The Post parameters i.e., shoot length, Root length, Fresh weight and Dry weight at 90 DAS was significantly increased in T3 – S.T with Pseudomonas fluorescens + neem oil (F.S) (42.76 cm), (13.06 cm), (172 gms), (37.96 gms) respectively as compared to control T0.

Microscopic and LF-RPA assay approaches to the detection of the fungal peanut pathogen Cercospora arachidicola

Peanut brown spot, caused by the fungus Cercospora arachidicola, represents a serious threat to global peanut production and is associated food security. The mechanisms whereby this fungus can penetrate the epidermis of infected plants, however, remain poorly understood. In this study, we found that C. arachidicola is able to enter pores and extend hyphae into leaves, thereby infecting peanut plants. Developing a tool that is well-suited to diagnose peanut brown spot in its early stages is vital to manage this disease effectively in the field. To that end, we combined a simplified DNA extraction method with a newly developed lateral flow strip-based recombinase polymerase amplification (LF-RPA) assay in order to facilitate the rapid and equipment-free detection of C. arachidicola. This assay recognizes highly conserved internal transcribed spacer (ITS) sequences associated with this pathogen and functions across a wide temperature range (25–45 °C). This approach positively identified all 12 tested C. arachidicola, without any cross-reactivity with other tested Cercospora species or fungal species. It was also able to detect DNA concentrations as low as 10−4 ng, making it 10 times more sensitive than traditional PCR-based approaches. By utilizing this LF-RPA assay in combination with a simplified PEG-NaOH-based approach to extracting DNA from plant samples, we were able to execute the entire protocol in just 30 min without the need for special equipment, thus allowing us to detect C. arachidicola in artificially infected peanut plants. The LF-RPA assay established herein is simple, rapid, and cost-effective, and is potentially amenable to further development as a diagnostic kit for the diagnosis of peanut brown spot in resource-limited settings or the field.

Image processing system for identifying groundnut plant disease

Groundnuts (Arachis hypogaea), also known as peanuts are the edible seeds of a legume plant that grow to maturity in the ground. Diseases and its diagnosis methodology are the main challenges to groundnut production. Manual means of identifying plant disease is the most difficult activity with a high rate of mistake and time taking procedures. Therefore, the main aim of this research was to design an image processing system to identify groundnut plant disease. In general, the major significance of the study is to provide effective and simple groundnut plant disease diagnosis system that supports disease controlling mechanism and experts in the domain area. While the process of developing the system, researchers used purposive sampling techniques for acquiring 320 sample leaves images from four classes of groundnuts plant. Those are Cercospora personatum, Cercospora arachidicola, Puccinia arachidis, and healthy leaf from Bishan-Babile and Gemechu peasant associations in Babile district, and Awdal peasant association in Gursum districts in East Hararghe zone of Oromiya Regional State. Also, the researchers conducted a survey study which helps to identify experts view and deep understanding of the domain area. The design, phase used; adaptive median filtering, K-means clustering, SVM and ANN techniques with MATLAB programming tool. In general, the overall result shows that the developed system achieved a better result with an accuracy of 90.6%.

​Management of Early Leaf Spot (Cercospora arachidicola) of Groundnut in Rajasthan

Background: Early leaf spot caused by Cercospora arachidicola Hori. is most destructive disease in all the groundnut growing areas of Rajasthan, under severe infestation it cause 30-50% losses in pod yield. Recently, Central Insecticide Board (CIB), Faridabade banned 27 pesticides including some important fungicides which are extensively used in plant disease management. Therefore, in the present investigation, our main emphasis was to find out some new fungicides for management of early leaf spot disease. Methods: Ten fungicides (hexaconazole 5% EC, difenconazole 25% EC, propiconazole 25% EC, tebuconazole 25.9% EC, trifloxystrobin 25% + tebuconazole 50% WG, mancozeb 50% WP, chlorothalonil 75% WP, carbendazim 50% WP, carbendazim 12% + mancozeb 63% WP and captan 70% + hexaconazole 5% WP) were evaluated against early leaf spot pathogen (C. arachidicola) both in lab as well as in field condition. The experiment was conducted at ARS, SKRAU, Bikaner during Kharif-2019 on most popular cv. HNG-69 in RBD design with the application of foliar spray of ten different fungicides at different concentrations against early leaf spot disease and compared with an untreated control. Result: Among all the fungicides used in the present investigation, Tebuconazole 25.9% EC was found most effective in inhibiting the mycelial growth of the pathogen followed by trifloxystrobin 25% + tebuconazole 50% WG. Under field condition, it gave maximum (70.73%) disease control with highest pod yield (31.5 q/ha) and net return (Rs 57,500/ha) when applied as foliar spray at 0.1% concentration followed by trifloxystrobin 25% + tebuconazole 50% WG at 0.2%. These treatments can provide an effective and economical management of early leaf spot disease for groundnut cultivators.

Synthesis, Antifungal Activity, 3D-QSAR, and Molecular Docking Study of Novel Menthol-Derived 1,2,4-Triazole-thioether Compounds.

A series of novel menthol derivatives containing 1,2,4-triazole-thioether moiety were designed, synthesized, characterized structurally, and evaluated biologically to explore more potent natural product-based antifungal agents. The bioassay results revealed that at 50 μg/mL, some of the target compounds exhibited good inhibitory activity against the tested fungi, especially against Physalospora piricola. Compounds 5b (R = o-CH3 Ph), 5i (R = o-Cl Ph), 5v (R = m,p-OCH3 Ph) and 5x (R = α-furyl) had inhibition rates of 93.3%, 79.4%, and 79.4%, respectively, against P. piricola, much better than that of the positive control chlorothalonil. Compounds 5v (R = m,p-OCH3 Ph) and 5g (R = o-Cl Ph) held inhibition rates of 82.4% and 86.5% against Cercospora arachidicola and Gibberella zeae, respectively, much better than that of the commercial fungicide chlorothalonil. Compound 5b (R = o-CH3 Ph) displayed antifungal activity of 90.5% and 83.8%, respectively, against Colleterichum orbicalare and Fusarium oxysporum f. sp. cucumerinum. Compounds 5m (R = o-I Ph) had inhibition rates of 88.6%, 80.0%, and 88.0%, respectively, against F. oxysporum f. sp. cucumerinu, Bipolaris maydis and C. orbiculare. Furthermore, compound 5b (R = o-CH3 Ph) showed the best and broad-spectrum antifungal activity against all the tested fungi. To design more effective antifungal compounds against P. piricola, 3D-QSAR analysis was performed using the CoMFA method, and a reasonable 3D-QSAR model (r2 = 0.991, q2 = 0.514) was established. The simulative binding pattern of the target compounds with cytochrome P450 14α-sterol demethylase (CYP51) was investigated by molecular docking.

Evaluation of Varying Rates of Mancozeb fungicide and Some Plant Leaf Powders as Seed Treatment and their cost-benefit for the Management of Early Leaf Spot (Cercospora arachidicola Hori) Disease of Groundnut in Makurdi, Nigeria

Field experiment were carried out during the first and second cropping seasons (2013//2014) at the Teaching and Research Farm of the Federal University of Agriculture Makurdi, Benue State of Nigeria, the effect of seed treatments with varying rates of Mancozeb fungicide, Pawpaw and Moringa leaf powders on early leaf spot incidence and ground nut yield was studied; and the cost benefit ratios calculated. The seed treatments were: Mancozeb, Moringa leaf powder and Pawpaw leaf powder while the seed treatments rates were 0.0 (control), 2.0, 2.5 and 3.0gm. Groundnut variety Benue AGR seeds were treated with the seed treatment rates replicated 3 times and arranged in a randomized complete block design (RCBD). Results of the first season and second seasons showed that seed treatment with Mancozeb significantly gave the highest plant establishment followed by moringa leaf powder and pawpaw leaf powder respectively. In the first year, 3.0g seed treatment significantly gave the highest plant establishment while the untreated control recorded the lowest plant establishment, but was not significantly difference (P ≤ 0.05) amongst the treatment rates in the second year. In the two cropping seasons, plants grown from seed treated with mancozeb recorded the lowest incidence of early leaf spot disease followed by moringa leaf powder at 40, 47 and 54 DAS respectively. Seed treatment rate of 3.0gm gave the lowest disease incidence from 40 to 54 DAS. At 90 DAS of the first season, seed treatment with Mancozeb significantly lowered the leaf defoliation followed by Moringa leaf powder compared to Pawpaw leaf powder. Similarly, during the second season, seed treatment with Mancozeb also reduced the leaf defoliation compared to the plant powders at 70, 80 and 90 DAS respectively. Mancozeb and Moringa leaf powder gave higher grain yield compared to Pawpaw leaf powder in the first season. Increase in seed treatment rate resulted to higher percentage increment in grain and haulm ............

Evaluation of Leaf Spot Resistance in Wild Arachis Species of Section Arachis

ABSTRACT Wild diploid Arachis species are potential sources of resistance to early (ELS) and late (LLS) leaf spot diseases caused by Passalora arachidicola (syn. Cercospora arachidicola Hori), and Nothopassalora personata (syn. Cercosporidium personatum (Berk. & Curt.) Deighton), respectively. Within section Arachis, limited information is available on the extent of genetic variation for resistance to these fungal pathogens. A collection of 78 accessions representing 15 wild species of Arachis section Arachis from the U.S peanut germplasm collection was evaluated for resistance to leaf spots. Screening was conducted under field (natural inoculum) conditions in Dawson, Georgia, during 2017 and 2018. Accessions differed significantly (P < 0.01) for all three disease variables evaluated, which included final defoliation rating, ELS lesion counts, and LLS lesion counts. Relatively high levels of resistance were identified for both diseases, with LLS being the predominant pathogen during the two years of evaluation. This research documents new sources of resistance to leaf spot diseases selected from an environment with high inoculum pressure. The presence of ELS and LLS enabled the selection of resistant germplasm for further introgression and pre-breeding.

Synthesis, Antifungal Activity, and 3D-QSAR Study of Novel Nopol-Derived 1,3,4-Thiadiazole-Thiourea Compounds.

A series of novel nopol derivatives bearing the 1,3,4-thiadiazole-thiourea moiety were designed and synthesized by multi-step reactions in search of potent natural product-based antifungal agents. Their structures were confirmed by FT-IR, NMR, ESI-MS, and elemental analysis. Antifungal activity of the target compounds was preliminarily evaluated by in vitro methods against Fusarium oxysporum f. sp. cucumerinum, Cercospora arachidicola, Physalospora piricola, Alternaria solani, Gibberella zeae, Rhizoeotnia solani, Bipolaris maydis, and Colleterichum orbicalare at 50 µg/mL. All the target compounds exhibited better antifungal activity against P. piricola, C. arachidicola, and A. solani. Compound 6j (R = m, p-Cl Ph) showed the best broad-spectrum antifungal activity against all the tested fungi. Compounds 6c (R = m-Me Ph), 6q (R = i-Pr), and 6i (R = p-Cl Ph) had inhibition rates of 86.1%, 86.1%, and 80.2%, respectively, against P. piricola, much better than that of the positive control chlorothalonil. Moreover, compounds 6h (R = m-Cl Ph) and 6n (R = o-CF3 Ph) held inhibition rates of 80.6% and 79.0% against C. arachidicola and G. zeae, respectively, much better than that of the commercial fungicide chlorothalonil. In order to design more effective antifungal compounds against A. solani, analysis of the three-dimensional quantitative structure–activity relationship (3D-QSAR) was carried out using the CoMFA method, and a reasonable and effective 3D-QSAR model (r2 = 0.992, q2 = 0.753) has been established. Furthermore, some intriguing structure–activity relationships were found and are discussed by theoretical calculation.

English

Early leaf spot caused by Cercospora arachidicola is the major destructive foliar disease of cultivated peanut in Shandong province of China. Understanding the genetic variability of this pathogen is crucial for evolutionary comprehension and breeding strategies. The genetic diversity of C. arachidicola isolates obtained from different peanut growing regions of Shandong province were assessed using inter-simple sequence repeats (ISSR) markers. Thirteen ISSR primers generating polymorphic, clearly discernible and reproducible patterns were screened out for further analysis. A total of 113 distinct bands were amplified, of which 85.8% were polymorphic, suggesting high values of polymorphism among the isolates. Cluster analysis using UPGMA indicated that all the isolates tested were separated into three distinct generic groups. The genetic relatedness of C. arachidicola isolates roughly coincided with geographical origin. Analysis of molecular variance (AMOVA) revealed that the observed genetic variation mainly existed within populations, and the variation among populations was weak. This study characterized the genetic diversity of C. arachidicola isolates for the first time, which will provide necessary genetic information for effective management practices. © 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers © 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers© 2021 Friends Science Publishers©

Discovery of Cysteine and Its Derivatives as Novel Antiviral and Antifungal Agents.

Based on the structure of the natural product cysteine, a series of thiazolidine-4-carboxylic acids were designed and synthesized. All target compounds bearing thiazolidine-4-carboxylic acid were characterized by 1H-NMR, 13C-NMR, and HRMS techniques. The antiviral and antifungal activities of cysteine and its derivatives were evaluated in vitro and in vivo. The results of anti-TMV activity revealed that all compounds exhibited moderate to excellent activities against tobacco mosaic virus (TMV) at the concentration of 500 μg/mL. The compounds cysteine (1), 3–4, 7, 10, 13, 20, 23, and 24 displayed higher anti-TMV activities than the commercial plant virucide ribavirin (inhibitory rate: 40, 40, and 38% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively), especially compound 3 (inhibitory rate: 51%, 47%, and 49% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively) with excellent antiviral activity emerged as a new antiviral candidate. Antiviral mechanism research by TEM exhibited that compound 3 could inhibit virus assembly by aggregated the 20S protein disk. Molecular docking results revealed that compound 3 with higher antiviral activities than that of compound 24 did show stronger interaction with TMV CP. Further fungicidal activity tests against 14 kinds of phytopathogenic fungi revealed that these cysteine derivatives displayed broad-spectrum fungicidal activities. Compound 16 exhibited higher antifungal activities against Cercospora arachidicola Hori and Alternaria solani than commercial fungicides carbendazim and chlorothalonil, which emerged as a new candidate for fungicidal research.

Biochemical changes in groundnut cultivars against early leaf spot disease (Cercospora arachidicola)

Biochemical changes in groundnut cultivars against early leaf spot disease (Cercospora arachidicola)

Evaluation of plant extracts for the management of Cercospora leaf spot of groundnut (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is a leguminous crop with high economic and nutritional value. However, increased production is hampered by Cercospora leaf spot (CLS) caused by Cercospora arachidicola and Cercosporidium personatum. Studies were conducted in vitro and in vivo to evaluate the efficacy of aqueous extracts of desert date seed (DDSE), neem seed (NSE), jatropha seed (JSE) and tobacco leaf (TLE) for the management of CLS. The antifungal activities of 25, 50, 75 and 100 g/l concentrations of each of the plant extracts was assessed in vitro on potato dextrose agar using the food poison technique. The field study was a factorial experiment consisting of 18 treatments laid in a Randomised Complete Block Design with four replications over two cropping seasons. The in vitro results revealed that all the botanicals at 100 g/l recorded the highest inhibition percentages. DDSE at 100 g/l significantly (P < 0.001) inhibited the highest mycelia growths compared to other levels of plant extracts used with inhibition percentages of 90.33 and 84.96% in C. arachidicola and C. personatum, respectively. Three out of the four aqueous extracts (DDSE, NSE and JSE) at 100 g/l significantly (P < 0.05) lowered disease incidence, severity and defoliation in the field and increased yield. Pod yield was significantly (P < 0.05) higher in plants treated with JSE, NSE, DDSE and Topsin-M, compared to those treated with TLE and the negative control plants. For most of the parameters, DDSE produced similar results as Topsin-M followed by NSE and JSE. Farmers can adopt DDSE, NSE and JSE as alternatives to fungicides leading to minimal effect on the environment since they are biodegradable. Key words: Cercospora leaf spot, plant extracts, groundnut, incidence, severity, aqueous.

Genome-wide detection of markers associated with early leaf spot and pod weight in groundnut using SNP and DArT markers

ABSTRACT Early leaf spot (ELS) disease, caused by Cercospora arachidicola S. Hori, severely affects groundnut (Arachis hypogaea L.) production worldwide. Breeding for resistant varieties using conventional breeding is difficult because multiple genes control the resistance and heritability is moderate. Our objective was to identify marker-trait associations (MTAs) for ELS resistance in a mini-core collection of 168 accessions. The accessions were genotyped using diversity array technology (DArTseq™) and phenotyped at two locations with and without inoculation. Two types of DArTseq markers were scored; Silico DArT markers and biallelic single nucleotide polymorphism (SNP) markers. Genotype effects were significant for both ELS and pod weight (PW), with several accessions showing good levels for resistance. The heritability of ELS was moderate (0.37 to 0.64), whereas heritability for PW was low (0.10 to 0.18). The DArTseq generated 3592 biallelic SNP markers and 15,237 dominant silico markers. The distribution of the biallelic and dominant markers across the genome shows that chromosomes B04 and A04 had the highest number of markers. The MTA analysis revealed 25 significant (p < 0.001) MTAs. One MTA for ELS was found across treatments and rating dates and may be suitable for marker-assisted selection upon validation. No MTA for PW was repeatable. The germplasm and markers identified in this study can serve as useful genomic resources to initiate marker-assisted selection and trait introgression for ELS resistance in groundnut.

Expression of Tcchitinase-I gene in transgenic peanut (Arachis hypogaea L.) confers enhanced resistance against leaf spot and rust diseases

The disease-resistant transgenic peanut cv ICG 13942 plants were developed by using Tcchitinase-I gene. Agrobacterium tumefaciens strain LBA4404 harboring the binary vector (pBinAR) contains the chitinase (Tcchitinase-I) gene and neomycin phosphotransferase resistance (nptII) gene. The transformed shoots were developed on selection medium (MMS + 0.5 mg/L IAA + 15 mg/L TDZ + 100 mg/L Kan + 250 mg/L Cefotaxime) from deembryonated cotyledon (DC) explants. Established plantlets were screened for the presence of Tcchitinase-I and nptII genes. Stable integration and expression of the transgenes (T0) were confirmed by using PCR, RT-PCR and Southern blot analyses. The transformation frequency 63.34% was recorded. All the transformed (T0) plants were found normal, flowered and set seeds. After selfing the T0 plants, a Mendelian inheritance pattern (3:1) for the transgene in T1 progeny is revealed. T1 transgenic peanut plants were evaluated for resistance against Cercospora arachidicola, C. personatum and Puccinia arachidis by infection with the microspores using detached leaf assay. These T1 plants have shown longer incubation, latent period and lower infection frequencies in comparison to non-transformed (WT) plants. The Tcchitinase-I gene expression in resistant transgenic plants was compared to that of a susceptible control. A significant negative correlation was recorded between chitinase activity and the frequency of infection to the three tested disease causing agents.

Antifungal Activity of Stabilized Ortho Silicic Acid (OSA) against Foliar Plant Pathogens

Present study was aimed to evaluate antifungal activity of stabilized ortho silicic acid (OSA) against foliar pathogens under in vitro and in vivo conditions. Studies were conducted using a commercial formulation of stabilized ortho silicic acid (2.0%, Silixol™ OSA). Activity of OSA was evaluated on thirteen fungal pathogens (Alternaria alternata, Alternaria macrospora, Alternaria solani, Cercospora arachidicola, Colletotrichum gloeosporioides, Corynespora cassiicola, Curvularia lunata, Bipolaris sorokiniana, Mycosphaerella fragariae, Mycopshaerella musicola, Phoma obscurans, Phyllosticta arachidis-hypogaeae, and Pyricularia oryzae) using Poison Food Technique. Silixol OSA exhibited a differential activity against all test pathogens. Out of thirteen pathogens, eight exhibited more than 50% inhibition of mycelial growth. Silixol OSA had induced ultrastructure changes in both fungal mycelium and spores. Pathogens with more than 50% inhibition, based on Poison Food Technique, were tested further by in vivo studies. OSA sprayed plants had healthy leaves and exhibited less disease severity. Results of the present study elucidate potential application of stabilized OSA in Integrated Disease Management Program (IDMP) to avoid reliance on synthetic fungicides.

Peanut (Arachis hypogaea) transcriptome revealed the molecular interactions of the defense mechanism in response to early leaf spot fungi (Cercospora arachidicola)

Cercospora arachidicola fungus is a causative agent of early leaf spot disease in peanut (Arachis hypogaea). However, little has been reported about the molecular interactions for defense mechanisms in the peanut plant against the fungal attack. In this study, we used RNA-Seq to analyse the expression profile of resistant (GPBD-4) and susceptible (JL-24) genotypes of peanut against C. arachidicola infection. A total of 91,734,735 raw reads were generated from RNA-Seq data. Differentially expressed genes (DEGs) were analysed for Gene Ontology to find essential genes responsible for defense mechanisms and to study their pathways by KEGG analysis. The resistant variety was able to withstand biotic stress due to exclusive up-regulation of defense-related genes (thaumatin, glutathione peroxidase, and cinnamyl alcohol dehydrogenase), while the susceptible variety was more prone to damage by infection due to down-regulation of genes including (F-box, cytochrome p450, Leucine-rich repeat protein kinase and terpene synthase) associated with a majority of biological function. RNA-Seq profile was validated by Reverse Transcriptase qPCR (RT-qPCR) technique, which showed a high correlation (R2 = 0.92) with the gene expression profile of RNA-Seq analysis. A total of 8591 EST-SSR markers were developed from the transcriptome library and 15 PCR primers based on microsatellite markers were used to validate SSR amplification. This study provides insight into the understanding of molecular interactions between plant and pathogen, and will also help to generate molecular markers for genetic mapping of peanut.

Synthesis, biological activities, and 3D-QSAR studies of (R)-2-phenyl-4,5-dihydrothiazole-4-carboxamide derivatives containing a sulfonohydrazide moiety

To discover a novel lead structure for antiphytopathogenic fungus agent, a series of (R)-2-phenyl-4,5-dihydrothiazole-4-carboxamide derivatives containing a sulfonohydrazide moiety were designed and synthesized. They were determined by melting points, 1H NMR, 13C NMR, and elemental analysis (EA). The biological activity results revealed that these title compounds possessed antifungal and insecticidal activities. Some title compounds against Alternaria solani, Physalospora piricola, Cercospora arachidicola, Phytophthora capsici, Fusarium graminearum, and Sclerotinia sclerotiorum displayed moderate to good antifungal activities at 50 mg/L, especially, compounds 6b and 6p displayed good and broad-spectrum antifungal activities. The structure activity relationships were discussed. A 3D-QSAR model was established based on the antifungal activity against Phytophthora capsici, indicating that electrostatic and hydrophobic fields were the two most significant factors for antifungal activity. Hence, structure optimization based on the CoMSIA model was performed to find compound 6p with excellent activity against Phytophthora capsici, and the EC50 values of compound 6p were comparable to those of chlorothalonil. Furthermore, the insecticidal activity of compound 6p against Culex pipiens larvae at 1 mg/L was considerable to that of chlorantraniliprole. Therefore, compound 6p can be used as a novel lead structure for antiphytopathogenic fungus and insecticidal agent development.