Metabolomics-Driven Mining of Metabolite Resources: Applications and Prospects for Improving Vegetable Crops

Vegetable crops possess a prominent nutri-metabolite pool that not only contributes to the crop performance in the fields, but also offers nutritional security for humans. In the pursuit of identifying, quantifying and functionally characterizing the cellular metabolome pool, biomolecule separation technologies, data acquisition platforms, chemical libraries, bioinformatics tools, databases and visualization techniques have come to play significant role. High-throughput metabolomics unravels structurally diverse nutrition-rich metabolites and their entangled interactions in vegetable plants. It has helped to link identified phytometabolites with unique phenotypic traits, nutri-functional characters, defense mechanisms and crop productivity. In this study, we explore mining diverse metabolites, localizing cellular metabolic pathways, classifying functional biomolecules and establishing linkages between metabolic fluxes and genomic regulations, using comprehensive metabolomics deciphers of the plant’s performance in the environment. We discuss exemplary reports covering the implications of metabolomics, addressing metabolic changes in vegetable plants during crop domestication, stage-dependent growth, fruit development, nutri-metabolic capabilities, climatic impacts, plant-microbe-pest interactions and anthropogenic activities. Efforts leading to identify biomarker metabolites, candidate proteins and the genes responsible for plant health, defense mechanisms and nutri-rich crop produce are documented. With the insights on metabolite-QTL (mQTL) driven genetic architecture, molecular breeding in vegetable crops can be revolutionized for developing better nutritional capabilities, improved tolerance against diseases/pests and enhanced climate resilience in plants.

Inter-Genera Colonization of Ocimum tenuiflorum Endophytes in Tomato and Their Complementary Effects on Na+/K+ Balance, Oxidative Stress Regulation, and Root Architecture Under Elevated Soil Salinity

Endophytic bacilli of ethano-botanical plant Ocimum tenuiflorum were screened for salt stress-alleviating traits in tomato. Four promising O. tenuiflorum endophytes (Bacillus safensis BTL5, Bacillus haynesii GTR8, Bacillus paralicheniformis GTR11, and Bacillus altitudinis GTS16) were used in this study. Confocal scanning laser microscopic studies revealed the inter-genera colonization of O. tenuiflorum endophytes in tomato plants, giving insights for widening the applicability of potential endophytes to other crops. Furthermore, in a pot trial under 150 mM NaCl concentration, the inoculated endophytes contributed in reducing salt toxicity and improving recovery from salt-induced oxidative stress by different mechanisms. Reduction in reactive oxygen species (ROS) (sub-cellular H₂O₂ and superoxide) accumulation was observed besides lowering programmed cell death and increasing chlorophyll content. Endophyte inoculation supplemented the plant antioxidant enzyme system via the modulation of enzymatic antioxidants, viz., peroxidase, ascorbate peroxidase, superoxide dismutase, and catalase, apart from increasing proline and total phenolics. Antioxidants like proline have dual roles of antioxidants and osmoregulation, which might also have contributed to improved water relation under elevated salinity. Root architecture, viz., root length, projection area, surface area, average diameter, tips, forks, crossings, and the number of links, was improved upon inoculation, indicating healthy root growth and enhanced nutrient flow and water homeostasis. Regulation of Na⁺/K⁺ balance and water homeostasis in the plants were also evident from the modulation in the expression of abiotic stress-responsive genes, viz., LKT1, NHX1, SOS1, LePIP2, SlERF16, and SlWRKY39. Shoot tissues staining with light-excitable Na⁺ indicator Sodium Green^TM Tetra (tetramethylammonium) salt showed low sodium transport and accumulation in endophyte-inoculated plants. All four endophytes exhibited different mechanisms for stress alleviation and indicated complementary effects on plant growth. Furthermore, this could be harnessed in the form of a consortium for salt stress alleviation. The present study established inter-genera colonization of O. tenuiflorum endophytes in tomato and revealed its potential in maintaining Na⁺/K⁺ balance, reducing ROS, and improving root architecture under elevated salinity.

Stage-dependent concomitant microbial fortification improves soil nutrient status, plant growth, antioxidative defense system and gene expression in rice

Stage-dependent concomitant fortification of rice (Oryza sativa L.) varieties PB1612 and CO51 with microbial inoculants Trichoderma asperellum and Pseudomonas fluorescens as seed coating, seedling root inoculation and soil application enhanced growth, activated antioxidant enzymes and modulated defence-related genes in plants. Microbial inoculants improved shoot height, tiller numbers, fresh weight and dry biomass. Co-inoculation was more impactful in enhancing plant growth and development as compared to single inoculation. Single and co-inoculation improved organic carbon (OC) and N, P and K content in the soil substantially. Mean values between control and co-inoculation varied significantly for OC in PB1612 (p0.001) and CO51 (p0.019) and phosphorus content in PB1612 (p0.044) and CO51 (p0.021). Microbial inoculation enhanced soil nutrients and increased their bioavailability for the plants. Total polyphenolics, flavonoids and protein content increased in the leaves following microbial inoculation. Enhanced non-enzymatic antioxidant parameters (ABTS, DPPH, Fe-ion reducing power and Fe-ion chelation) was found in microbe inoculated rice reflecting high free radical scavenging activity in polyphenolics-rich leaf extracts. Increased enzyme activity of superoxide dismutase (SOD), glutathione reductase (GR), phenylalanine ammonia-lyase (PAL), peroxidase (PO), glutathione peroxidase (GPX), ascorbate peroxidase (APX) and catalase (CAT) showed improved ROS scavenging in rice plants having co-inoculation. Over-expression of PAL, cCuZn-SOD and CAT genes in microbial inoculated rice plants was recorded. The study concludes that plant stage-wise concomitant fortification by microbial inoculants could play multi-pronged manifestations at physiological, biochemical and molecular level in rice to positively influence growth, development and defense attributes in plants.

Sphingobacterium sp. BHU-AV3 Induces Salt Tolerance in Tomato by Enhancing Antioxidant Activities and Energy Metabolism

Salt tolerant bacteria can be helpful in improving a plant's tolerance to salinity. Although plant-bacteria interactions in response to salt stress have been characterized, the precise molecular mechanisms by which bacterial inoculation alleviates salt stress in plants are still poorly explored. In the present study, we aimed to determine the role of a salt-tolerant plant growth-promoting rhizobacteria (PGPR) Sphingobacterium BHU-AV3 for improving salt tolerance in tomato through investigating the physiological responses of tomato roots and leaves under salinity stress. Tomato plants inoculated with BHU-AV3 and challenged with 200 mM NaCl exhibited less senescence, positively correlated with the maintenance of ion balance, lowered reactive oxygen species (ROS), and increased proline content compared to the non-inoculated plants. BHU-AV3-inoculated plant leaves were less affected by oxidative stress, as evident from a reduction in superoxide contents, cell death, and lipid peroxidation. The reduction in ROS level was associated with the increased antioxidant enzyme activities along with multiple-isoform expression [peroxidase (POD), polyphenol oxidase (PPO), and superoxide dismutase (SOD)] in plant roots. Additionally, BHU-AV3 inoculation induced the expression of proteins involved in (i) energy production [ATP synthase], (ii) carbohydrate metabolism (enolase), (iii) thiamine biosynthesis protein, (iv) translation protein (elongation factor 1 alpha), and the antioxidant defense system (catalase) in tomato roots. These findings have provided insight into the molecular mechanisms of bacteria-mediated alleviation of salt stress in plants. From the study, we can conclude that BHU-AV3 inoculation effectively induces antioxidant systems and energy metabolism in tomato roots, which leads to whole plant protection during salt stress through induced systemic tolerance.

Microbial inoculation in rice regulates antioxidative reactions and defense related genes to mitigate drought stress

Microbial inoculation in drought challenged rice triggered multipronged steps at enzymatic, non-enzymatic and gene expression level. These multifarious modulations in plants were related to stress tolerance mechanisms. Drought suppressed growth of rice plants but inoculation with Trichoderma, Pseudomonas and their combination minimized the impact of watering regime. Induced PAL gene expression and enzyme activity due to microbial inoculation led to increased accumulation of polyphenolics in plants. Enhanced antioxidant concentration of polyphenolics from microbe inoculated and drought challenged plants showed substantially high values of DPPH, ABTS, Fe-ion reducing power and Fe-ion chelation activity, which established the role of polyphenolic extract as free radical scavengers. Activation of superoxide dismutase that catalyzes superoxide (O2-) and leads to the accumulation of H2O2 was linked with the hypersensitive cell death response in leaves. Microbial inoculation in plants enhanced activity of peroxidase, ascorbate peroxidase, glutathione peroxidase and glutathione reductase enzymes. This has further contributed in reducing ROS burden in plants. Genes of key metabolic pathways including phenylpropanoid (PAL), superoxide dismutation (SODs), H2O2 peroxidation (APX, PO) and oxidative defense response (CAT) were over-expressed due to microbial inoculation. Enhanced expression of OSPiP linked to less-water permeability, drought-adaptation gene DHN and dehydration related stress inducible DREB gene in rice inoculated with microbial inoculants after drought challenge was also reported. The impact of Pseudomonas on gene expression was consistently remained the most prominent. These findings suggested that microbial inoculation directly caused over-expression of genes linked with defense processes in plants challenged with drought stress. Enhanced enzymatic and non-enzymatic antioxidant reactions that helped in minimizing antioxidative load, were the repercussions of enhanced gene expression in microbe inoculated plants. These mechanisms contributed strongly towards stress mitigation. The study demonstrated that microbial inoculants were successful in improving intrinsic biochemical and molecular capabilities of rice plants under stress. Results encouraged us to advocate that the practice of growing plants with microbial inoculants may find strategic place in raising crops under abiotic stressed environments.

Trichoderma mediate early and enhanced lignifications in chickpea during Fusarium oxysporum f. sp. ciceris infection

Lignifications in secondary cell walls play a significant role in defense mechanisms of plants against the invading pathogens. In the present study, we investigated Trichoderma strain specific lignifications in chickpea plants pre-treated with 10 potential Trichoderma strains and subsequently challenged with the wilt pathogen Fusarium oxysporum f. sp. ciceris (Foc). Trichoderma-induced lignifications in chickpea were observed through histochemical staining and expression of some genes of the lignin biosynthetic pathway. Lignifications were observed in transverse sections of shoots near the soil line through histochemical staining and expression pattern of the target genes was observed in root tissues through semi quantitative RT-PCR at different time intervals after inoculation of F. oxysporum f. sp. ciceris. Lignin deposition and expression pattern of the target genes were variable in each treatment. Lignifications were enhanced in all 10 Trichoderma strain treated and F. oxysporum f. sp. ciceris challenged chickpea plants. However, four Trichoderma strains viz., T-42, MV-41, DFL, and RO, triggered significantly high lignifications compared to the other six strains. Time course studies showed that effective Trichoderma isolates induced lignifications very early compared to the other strains and the process of lignifications nearly completes within 6 days of pathogen challenge. Thus, from the results it can be concluded that effective Trichoderma strains trigger lignifications very early in chickpea under Foc challenge and provide better protection to chickpea plants.

Trichoderma asperellum T42 Reprograms Tobacco for Enhanced Nitrogen Utilization Efficiency and Plant Growth When Fed with N Nutrients

Trichoderma spp., are saprophytic fungi that can improve plant growth through increased nutrient acquisition and change in the root architecture. In the present study, we demonstrate that Trichoderma asperellum T42 mediate enhancement in host biomass, total nitrogen content, nitric oxide (NO) production and cytosolic Ca2+ accumulation in tobacco. T42 inoculation enhanced lateral root, root hair length, root hair density and root/shoot dry mass in tobacco under deprived nutrients condition. Interestingly, these growth attributes were further elevated in presence of T42 and supplementation of NO3- and NH4+ nutrients to tobacco at 40 and 70 days, particularly in NO3- supplementation, whereas no significant increment was observed in nia30 mutant. In addition, NO production was more in tobacco roots in T42 inoculated plants fed with NO3- nutrient confirming NO generation was dependent on NR pathway. NO3- dependent NO production contributed to increase in lateral root initiation, Ca2+ accumulation and activities of nitrate transporters (NRTs) in tobacco. Higher activities of several NRT genes in response to T42 and N nutrients and suppression of ammonium transporter (AMT1) suggested that induction of high affinity NRTs help NO3- acquisition through roots of tobacco. Among the NRTs NRT2.1 and NRT2.2 were more up-regulated compared to the other NRTs. Addition of sodium nitroprusside (SNP), relative to those supplied with NO3-/NH4+ nutrition and T42 treated plants singly, and with application of NO inhibitor, cPTIO, confirmed the altered NO fluorescence intensity in tobacco roots. Our findings suggest that T42 promoted plant growth significantly ant N content in the tobacco plants grown under N nutrients, notably higher in NO3-, providing insight of the strategy for not only tobacco but probably for other crops as well to adapt to fluctuating nitrate availability in soil.

Compatible Rhizosphere-Competent Microbial Consortium Adds Value to the Nutritional Quality in Edible Parts of Chickpea

Chickpea is used as a high-energy and protein source in diets of humans and livestock. Moreover, chickpea straw can be used as alternative of forage in ruminant diets. The present study evaluates the effect of beneficial microbial inoculation on enhancing the nutritional values in edible parts of chickpea. Two rhizosphere-competent compatible microbes (Pseudomonas fluorescens OKC and Trichoderma asperellum T42) were selected and applied to seeds either individually or in consortium before sowing. Chickpea seeds treated with the microbes showed enhanced plant growth [88.93% shoot length at 60 days after sowing (DAS)] and biomass accumulation (21.37% at 120 DAS). Notably, the uptake of mineral nutrients, viz., N (90.27, 91.45, and 142.64%), P (14.13, 58.73, and 56.84%), K (20.5, 9.23, and 35.98%), Na (91.98, 101.66, and 36.46%), Ca (16.61, 29.46, and 16%), and organic carbon (28.54, 17.09, and 18.54%), was found in the seed, foliage, and pericarp of the chickpea plants, respectively. Additionally, nutritional quality, viz., total phenolic (59.7, 2.8, and 17.25%), protein (9.78, 18.53, and 7.68%), carbohydrate content (26.22, 30.21, and 26.63%), total flavonoid content (3.11, 9.15, and 7.81%), and reducing power (112.98, 75.42, and 111.75%), was also found in the seed, foliage, and pericarp of the chickpea plants. Most importantly, the microbial-consortium-treated plants showed the maximum increase of nutrient accumulation and enhancement in nutritional quality in all edible parts of chickpea. Nutritional partitioning in different edible parts of chickpea was also evident in the microbial treatments compared to their uninoculated ones. The results thus clearly demonstrated microbe-mediated enhancement in the dietary value of the edible parts of chickpea because seeds are consumed by humans, whereas pericarp and foliage (straw) are used as an alternative of forage and roughage in ruminant diets.

Trichoderma asperellum (T42) and Pseudomonas fluorescens (OKC)-Enhances Resistance of Pea against Erysiphe pisi through Enhanced ROS Generation and Lignifications

Plant signaling mechanisms are not completely understood in plant–fungal biotrophic pathogen interactions. Further how such interactions are influenced by compatible rhizosphere microbes are also not well-studied. Therefore, we explored the pea-Erysiphe pisi (obligate biotroph) system to understand the interaction and applied compatible rhizospheric bio-agents Trichoderma asperellum (T42) and Pseudomonas fluorescens (OKC) singly or in combination to assess their influence on the host while under the pathogen challenge. Transcript accumulation pattern of some vital genes in the lignin biosynthetic pathway in pea under E. pisi challenge indicated enhanced activation of the pathway. Interestingly, transcript accumulations were even higher in the bio-agent treated plants compared to untreated plants after pathogen inoculation particularly in co-inoculated treatments. Further, down regulation of the lignifications-associated ABC transporter gene in the pathogen challenged plants possibly is an indication of passive diffusion of monolignols across the membrane from symplast. Additionally, up regulation of NADPH oxidase gene revealed ROS generation in the challenged plants which was confirmed through spectrophotometric estimation of H₂O₂. Up regulation of laccase and peroxidase along with higher H₂O₂ generation points out their involvement in lignifications which was further confirmed through cross section analysis of pea stems that showed increased lignifications in pathogen challenged plants co-inoculated with the bioagents. Interestingly, pathogen responsive MAPK homologs MAPK3/MAPK6 and the enzyme serine threonine kinase that activates MAPKs were down regulated and the results possibly indicate non-participation of the MAPK cascade in this interaction. Therefore, it can be concluded that the microbial treatments enhanced pea resistance to E. pisi by generation of ROS and lignifications.

Multiple post-domestication origins of kabuli chickpea through allelic variation in a diversification-associated transcription factor

Chickpea (Cicer arietinum) is among the founder crops domesticated in the Fertile Crescent. One of two major forms of chickpea, the so-called kabuli type, has white flowers and light-colored seed coats, properties not known to exist in the wild progenitor. The origin of the kabuli form has been enigmatic. We genotyped a collection of wild and cultivated chickpea genotypes with 538 single nucleotide polymorphisms (SNPs) and examined patterns of molecular diversity relative to geographical sources and market types. In addition, we examined sequence and expression variation in candidate anthocyanin biosynthetic pathway genes. A reduction in genetic diversity and extensive genetic admixture distinguish cultivated chickpea from its wild progenitor species. Among germplasm, the kabuli form is polyphyletic. We identified a basic helix-loop-helix (bHLH) transcription factor at chickpea's B locus that conditions flower and seed colors, orthologous to Mendel's A gene of garden pea, whose loss of function is associated invariantly with the kabuli type of chickpea. From the polyphyletic distribution of the kabuli form in germplasm, an absence of nested variation within the bHLH gene and invariant association of loss of function of bHLH among the kabuli type, we conclude that the kabuli form arose multiple times during the phase of phenotypic diversification after initial domestication of cultivated chickpea.

Pseudomonas fluorescens and Trichoderma asperellum Enhance Expression of Gα Subunits of the Pea Heterotrimeric G-protein during Erysiphe pisi Infection

We investigated the transcript accumulation patterns of all three subunits of heterotrimeric G-proteins (Gα1 and 2, Gβ, and Gγ) in pea under stimulation of two soil-inhabiting rhizosphere microbes Pseudomonas fluorescens OKC and Trichoderma asperellum T42. The microbes were either applied individually or co-inoculated and the transcript accumulation patterns were also investigated after challenging the same plants with a fungal biotrophic pathogen Erysiphe pisi. We observed that mostly the transcripts of Gα 1 and 2 subunits were accumulated when the plants were treated with the microbes (OKC and T42) either individually or co-inoculated. However, transcript accumulations of Gα subunits were highest in the T42 treatment particularly under the challenge of the biotroph. Transcript accumulations of the other two subunits Gβ and Gγ were either basal or even lower than the basal level. There was an indication for involvement of JA-mediated pathway in the same situations as activation of LOX1 and COI1 were relatively enhanced in the microbe co-inoculated treatments. Non-increment of SA content as well as transcripts of SA-dependent PR1 suggested non-activation of the SA-mediated signal transduction in the interaction of pea with E. pisi under the stimuli of OKC and T42. Gα1 and 2 transcript accumulations were further correlated with peroxidases activities, H2O2 generation and accumulation in ABA in pea leaves under OKC and T42 stimulations and all these activities were positively correlated with stomata closure at early stage of the biotroph challenge. The microbe-induced physiological responses in pea leaves finally led to reduced E. pisi development particularly in OKC and T42 co-inoculated plants. We conclude that OKC and T42 pretreatment stimulate transcript accumulations of the Gα1 and Gα2 subunits of the heterotrimeric G protein, peroxidases activities and phenol accumulation in pea during infection by E. pisi. The signal transduction was possibly mediated through JA in pea under the stimulus of the microbes and the cumulative effect of the co-inoculated microbes had a suppressive effect on E. pisi conidial development on pea leaves.

Plant genotype, microbial recruitment and nutritional security

Agricultural food products with high nutritional value should always be preferred over food products with low nutritional value. Efforts are being made to increase nutritional value of food by incorporating dietary supplements to the food products. The same is more desirous if the nutritional value of food is increased under natural environmental conditions especially in agricultural farms. Fragmented researches have demonstrated possibilities in achieving the same. The rhizosphere is vital in this regard for not only health and nutritional status of plants but also for the microorganisms colonizing the rhizosphere. Remarkably robust composition of plant microbiome with respect to other soil environments clearly suggests the role of a plant host in discriminating its colonizers (Zancarini et al., 2012). A large number of biotic and abiotic factors are believed to manipulate the microbial communities in the rhizosphere. However, plant genotype has proven to be the key in giving the final shape of the rhizosphere microbiome (Berendsen et al., 2012; Marques et al., 2014).

Solid waste management of temple floral offerings by vermicomposting using Eisenia fetida

Recycling of temple waste (TW) mainly comprising of floral offerings was done through vermitechnology using Eisenia fetida and its impact on seed germination and plant growth parameters was studied by comparing with kitchen waste (KW) and farmyard waste (FYW) vermicompost (VC). The worm biomass was found to be maximum in TW VC compared to KW and FYW VCs at both 40 and 120days old VCs. Physico-chemical analysis of worm-worked substrates showed better results in TW VC especially in terms of electrical conductivity, C/N, C/P and TK. 10% TW VC-water extract (VCE) showed stimulatory effect on germination percentage of chickpea seeds while KW and FYW VCE proved effective at higher concentration. Variation in growth parameters was also observed with change in the VC-soil ratio and TW VC showed enhanced shoot length, root length, number of secondary roots and total biomass at 12.5% VC compared to KW and FYW VC.

Large-scale development of cost-effective single-nucleotide polymorphism marker assays for genetic mapping in pigeonpea and comparative mapping in legumes

Single-nucleotide polymorphisms (SNPs, >2000) were discovered by using RNA-seq and allele-specific sequencing approaches in pigeonpea (Cajanus cajan). For making the SNP genotyping cost-effective, successful competitive allele-specific polymerase chain reaction (KASPar) assays were developed for 1616 SNPs and referred to as PKAMs (pigeonpea KASPar assay markers). Screening of PKAMs on 24 genotypes [23 from cultivated species and 1 wild species (Cajanus scarabaeoides)] defined a set of 1154 polymorphic markers (77.4%) with a polymorphism information content (PIC) value from 0.04 to 0.38. One thousand and ninety-four PKAMs showed polymorphisms between parental lines of the reference mapping population (C. cajan ICP 28 × C. scarabaeoides ICPW 94). By using high-quality marker genotyping data on 167 F₂ lines from the population, a comprehensive genetic map comprising 875 PKAMs with an average inter-marker distance of 1.11 cM was developed. Previously mapped 35 simple sequence repeat markers were integrated into the PKAM map and an integrated genetic map of 996.21 cM was constructed. Mapped PKAMs showed a higher degree of synteny with the genome of Glycine max followed by Medicago truncatula and Lotus japonicus and least with Vigna unguiculata. These PKAMs will be useful for genetics research and breeding applications in pigeonpea and for utilizing genome information from other legume species.

Fertile plant regeneration from cryopreserved calli of Oryza rufipogon Griff. and assessment of variation in the progeny of regenerated plants

A protocol was developed for preservation of calli of Oryza rufipogon Griff. in liquid nitrogen (-196°C). Optimal conditions for cryoprotection, pre-freezing and post-thaw recovery of calli were identified. Cryoprotectant treatment at low temperature, pre-freezing in isopropanol bath for 1 h at -70°C, rapid thawing and proper removal of cryoprotectant were critical for post-thaw survival. Genetic fidelity of the R1 plants obtained from cryopreserved, cryoprotectant-treated and untreated calli was assessed by phenotypic and molecular characterization. Comparison of phenotypic characters with seed-derived control plants showed no significant variation in the agronomic characters, but seed physical characters showed significant reduction in all the in vitro generated plants. Molecular data generated using 26 rice simple sequence repeat markers showed 4.78-7.25% change from control. Results suggested that both callus induction and cryopreservation induced heritable variations in O. rufipogon. In addition, a combination of phenotypic and molecular characterization using an appropriate marker provided better insight into genetic fidelity of recovered plants.

Polyphenolics from various extracts/fractions of red onion (Allium cepa) peel with potent antioxidant and antimutagenic activities

In order to determine antioxidant activity, the five extracts/fractions of red onion peel were studied for their total content of phenolics (TPC), flavonoids (TFC), antioxidant activity (AOA), free radical scavenging activity (FRSA), assayed by DPPH radical in the terms of anti-radical power (ARP) and reducing power (RP), expressed as ascorbic acid equivalents (ASE)/ml. High TPC (384.7 +/- 5.0 mg GAE/g), TFC (165.2+/- 3.2 mg QE/g), AOA (97.4 +/- 7.6%), ARP (75.3 +/-4.5) and RP (1.6 +/-0.3 ASE/ml) were found for the ethyl acetate (EA) fraction. EA fraction had markedly higher antioxidant capacity than butylated hydroxytoluene (BHT) in preventive or scavenging capacities against FeCl3-induced lipid peroxidation, protein fragmentation, hydroxyl (site-specific and non-site-specific), superoxide anion and nitric oxide radicals. EA fraction also showed dose dependent antimutagenic activity by following the inhibition of tobacco-induced mutagenicity in Salmonella typhimurium strains (TA102) and hydroxyl radical-induced nicking in plasmid pUC18 DNA. HPLC and MS/MS analysis showed the presence of ferulic, gallic, protocatechuic acids, quercetin and kaempferol. The large amount of polyphenols contained in EA fraction may cause its strong antioxidant and antimutagenic properties. This information shows that EA fraction of red onion peel can be used as natural antioxidant in nutraceutical preparations.

Microwave absorption measurements using a broad-band meanderline approach

We describe a technique that permits broad-band, field-dependent ferromagnetic and electron paramagnetic resonance absorption measurements that is applicable to thin films and patterned micro-/nanostructured arrays and is based on a wire-wound meanderline approach. Techniques to prepare meanderlines and perform microwave measurements are described along with some demonstrations involving an electron paramagnetic resonance calibration/test material, 2,2-diphenyl-1-picryl-hydrazyl, and a ferromagnetic cobalt thin film.

Antioxidant and anti-quorum sensing activities of green pod of Acacia nilotica L

The antioxidant and anti-quorum sensing activities of eight extracts were studied in green pods of Acacia nilotica. The specific phenolic compositions and their quantifications were performed by HPLC and MS/MS, which showed that the HEF (pH 4) was higher in gallic acid, ellagic acid, epicatechin, rutin, and GTs. In order to find antioxidant potential of various extracts, their activities were studied for TPC, AOA, FRSA, RP, inhibition of LPO, FIC activity, HO* and O(2)(-) scavenging activities. Among them HEF (pH 4) has shown potent antioxidant activity. HEF (pH 4) was also found effective in protecting plasmid DNA and HAS protein oxidation induced by HO*. Pre-treatment of HEF (pH 4) at 75 and 150 mg/kg body weight for 6 days caused a significant increase in the levels of CAT and SOD and decrease in the level of MDA content in liver, lungs, kidneys and blood when compared to CCl(4)-intoxicated rats. Eventually, the extracts were also screened for anti-QS activity. Of these extracts two showed QS inhibition: HEF (pH 4) and HCE. The results obtained strongly indicate that green pod of A. nilotica are important source of natural antioxidants.

Control of Erysiphe pisi Causing Powdery Mildew of Pea (Pisum sativum) by Cashewnut (Anacardium occidentale) Shell Extract

The effect of methanolic extract of cashewnut (Anacardium occidentale) shell extract was seen on conidial germination of Erysiphe pisi and powdery mildew development in pea (Pisum sativum). Maximum conidial germination inhibition of E. pisi on glass slides was observed at 300 ppm. Similar effect on floated pea leaves was observed after 48 h at the same concentration. Conidial germination on intact untreated pea leaves was also assessed on II and IV nodal leaves while IV and II nodal leaves were treated with the extract and vice versa. There was tremendous reduction in conidial germination on all the nodal leaves. The disease intensity of pea powdery mildew was significantly reduced by methanolic extract of cashewnut shells. Maximum reduction was observed with 200 ppm where 39% disease intensity was recorded in comparison to 96.53% in the control. The phenolic acid content of pea leaves following treatments with this extract varied and no definite pattern was observed. Out of several phenolic compounds, namely, gallic, ferulic, chlorogenic, and cinnamic acids, only gallic acid was found to be present consistently in all the treatments with varied amounts.

Foliar Application of Plant Growth-Promoting Rhizobacteria Increases Antifungal Compounds in Pea (Pisum sativum) Against Erysiphe pisi

Systemic effect of two plant growth-promoting rhizobacterial (PGPR) strains,viz., Pseudomonas fluorescens (Pf4) and P. aeruginosa (Pag), was evaluated on pea (Pisum sativum) against the powdery mildew pathogen Erysiphe pisi. Foliar spray of the two PGPR strains was done on specific nodal leaves of pea and conidial germination of E. pisi was observed on other nodal leaves,distal to the treated ones. Conidial germination was reduced on distant leaves and at the same time,specific as well as total phenolic compounds increased in the leaves distal to those applied with PGPR strains,thereby indicating a positive correlation. The strains induced accumulation of phenolic compounds in pea leaves and the amount increased when such leaves were get inoculated with E. pisi conidia. Between the two strains, Pag was found to be more effective than Pf4 as its effect was more persistent in pea leaves. Foliar application of PGPR strains for the control of powdery mildew of pea is demonstrated in vitro while correlating it with the increased accumulation of plant phenolics.

Antifungal activity of 2-hydroxy 4,4'6'trimethoxy chalcone

Antifungal activity of 2-hydroxy 4,4'6'trimethoxy chalcone individually was tested against spore germination of ten fungi of different genera. Efficacy of the chemical was also tested against conidial germination and other growth parameters of Erysiphe pisi on excised pea leaves. 2-Hydroxy 4,4'6'trimethoxy chalcone inhibited spore germination at all the concentrations. Maximum inhibition was observed at 2000 ppm where more than 78 per cent inhibition of spore germination was observed in Ustilago cynodontis, Alternaria brassicicola, A. solani and Aspergillus flavus. It also reduced conidial germination of E. pisi significantly, when applied as pre-inoculation treatment.

Differential methods of inoculation of plant growth-promoting rhizobacteria induce synthesis of phenylalanine ammonia-lyase and phenolic compounds differentially in chickpca

Foliar spray and micro-injection of plant growth-promoting rhizobacterial species, viz. Pseudomonas fluorescens and P. aeruginosa on chickpea induced synthesis of phenylalanine ammonia-lyase (PAL) when tested against Sclerotinia sclerotiorum. Induction of PAL was also associated with increased synthesis of phenolic compounds such as tannic, gallic, caffeic, chlorogenic and cinnamic acids. Treatment with P. fluorescens was found to be more effective in inducing phenolic compounds as compared to P. aeruginosa. However, persistence of PAL activity was observed more with P. aeruginosa. Although both the inoculation methods were effective, foliar application was found to be superior to micro-injection in terms of rapid PAL activity leading to the synthesis of phenolic compounds.

Variation in Biochemical Composition among Indian Isolates of Sclerotinia sclerotiorum

Biochemical variability among 20 Indian isolates of Sclerotinia sclerotiorum collected from different hosts/soil samples from different localities in India is reported. High Performance Liquid Chromatographic (HPLC) analysis of ethyl acetate fraction of culture filtrate, mycelia, sclerotia and sclerotial exudate showed 15~23 peaks but only 11 could be identified. They were tannic, gallic, oxalic, caffeic, vanillic, ferulic, O-coumeric, chlorogenic, cinnamic, salicylic and gentisic acids. The amount of phenolic compounds varied among the culture filtrates, mycelia, sclerotia and sclerotial exudates of S. sclerotiorum.

Antifungal Activity of a Phytoterpenoid (AOS-A) Isolated from Artabotrytis odoratissimus on Spore Germination of Some Fungi

Phytoterpenoid isolated from Artabotrytis odoratissimus inhibited spore germination of some plant pathogenic as well as saprophytic fungi e.g. Alternaria alternata, A. solani, Cercospora sp., Curvularia maculans, C. pennisetti, Fusarium udum, Helminthosporium echinochlova, H. frumentacie, H. penniseti and Ustilago cynodontis. In Curvularia maculans and H. frumentacie, spore germination was completely inhibited at 2000 ppm. However, Curvularia maculans and C. pennisetti showed considerable sensitivity to this chemical even at 500 ppm.

Antifungal Activity of Narceine Methyl Ester and Narceine Isolated from Corydalis longipes Against Some Phytopathogenic Fungi

Narceine methyl ester and narceine are potent alkaloids which were isolated from Corydalis longipes were found effective in vitro at very low concentration, i.e., 100~500 ppm against spore germination of some test plant pathogenic fungi (Alternaria solani, A. tagetica, Cercospora abelmoschi, Curvularia maculans, Erysiphe cichoracearum, E. pisi, Fusarium udum, Helminthosporium oryzae, H. penniseti, Ustilago cynodontis). Among the test, phytopathogens the spores of F. udum, C. maculans and H. penniseti were highly sensitive at 200 ppm. However, spores of E. pisi, A. solani and A. tagetica were less sensitive at low concentration followed by other test fungi. Most of the fungi showed zero or nearly zero percent spore germination at 400 and 500 ppm.

Induction of Sexual Stage and Colony Morphology of Some Isolates of Sclerotium rolfsii Causing Spotted Leaf Rot in Plants

Twenty-two isolates of Sclerotium rolfsii causing spotted leaf rot from Varanasi, India were grown on 6% Cyperus rotundus rhizome meal agar (CRMA) medium for the induction of athelial stage (Athelia rolfsii). Only one isolate obtained from Sphaeranthus indicus formed basidial stage on CRMA medium while the other 21 isolates did not. Basidial stage was also produced in S. indicus isolate at different concentrations (5.5, 6.0 and 6.5% w/v) of CRMA medium. Size of basidia, sterigmata and basidiospores of this isolate was measured. Basidia clavate, hyaline and measured 10~12 × 4~5 µm in size, basidiospores hyaline, unicellular, subglobose to ellipsoid produced on sterigmata and measured 3~5 × 2~4µm in size, sterigmata hyaline and measured 4~5 × 1.5~2 µm in size. The results of the present study revealed wide variation in spotted leaf rot isolates of S. rolfsii. A reddish zone around the colony of S. rolfsii isolate from Vernonia sp. was observed on CRMA medium. HPLC analysis of the zone revealed the presence of gallic and ferulic acid which were also thought to be responsible for reduced mycelial growth of the isolate on CRMA medium.

Effect of plant growth-promoting Rhizobacteria and culture filtrate of Sclerotium rolfsii on phenolic and salicylic acid contents in chickpea (Cicer arietinum)

Two plant growth-promoting rhizobacteria (PGPR), viz., Pseudomonas fluorescens strain Pf4 and P. aeruginosa strain Pag, protected chickpea ( Cicer arietinum) plants from Sclerotium rolfsii infection when applied singly or in combination as seed treatment. Pag gave the best protection to the seedlings, applied either singly (mortality 16%) or in combination with Pf4 (mortality 17%) compared with 44% and 24% mortality in control and Pf4 treatment, respectively. The two PGPR strains induced the synthesis of specific phenolic acids, salicylic acid (SA), as well as total phenolics at different growth stages of chickpea seedlings with varied amount. The maximum amount of total phenolics was recorded in all the aerial parts of 4-week-old plants. Gallic, ferulic, chlorogenic, and cinnamic acids were the major phenolic acids detected in high-performance liquid chromatography (HPLC) analysis. Induction of such phenolic acids in the seedlings was observed up to 6 weeks in comparison with control. Salicylic acid (SA) was induced frequently during the first 3 weeks of growth only. Between the two strains, Pag was more effective in inducing phenolic acid synthesis applied either singly or in combination with strain Pf4 during the entire 6 weeks of growth of chickpea. In the presence of a culture filtrate of S. rolfsii, the two Pseudomonas strains induced more phenolic acids in treated than in non-treated and control plants. The occurrence of salicylic acid was frequent in the first 24 h, but infrequent at 48 and 96 h. Foliar spray of Pseudomonas strains also enhanced the phenolic acid content as well as total phenolics within 24 h of application. Gallic, chlorogenic, and cinnamic acids were consistently discerned in the treated leaves, whereas SA was absent even up to 96 h of application. Resistance in chickpea plants by Pseudomonas strains through induction of phenolic compounds as well as induced systemic resistance via SA-dependent pathway was evident.

Variability in Indian isolates of Sclerotium rolfsii

Variability among 26 isolates of Sclerotium rolfsii collected from various hosts/soil samples and localities in India is reported. The isolates varied in colony morphology, mycelial growth rate, sclerotium formation, teleomorph production and sclerotial size and color. Out of 26 isolates, only 4 produced the teleomorph stage on Cyperus rotundus rhizome meal agar medium. Mycelial incompatibility among the isolates was also seen, and out of 325 combinations, only 29 combinations (8.9%) showed compatible reactions. Based on mycelial compatibility, 13 vegetative incompatibility groups (VCG) were identified among the isolates. HPLC analysis of the ethyl acetate fraction of culture filtrates of the isolates revealed 10-22 peaks. Six peaks were identified as gallic, oxalic, ferulic, indole-3-acetic acid (IAA), chlorogenic, and cinnamic acids. Oxalic, IAA, and cinnamic acids were present in the culture filtrates of all the isolates in varying amounts. The other three phenolic acids were not detected in some of the isolates. A comparative HPLC analysis of sclerotial exudate, sclerotia, mycelia, and culture filtrates of two S. rolfsii isolates (leaf spot- and collar rot-causing) producing different symptoms on their respective hosts revealed variation in the content of phenolic acids, IAA, and oxalic acid.

Plant growth-promoting rhizobacteria-mediated induction of phenolics in pea ( Pisum sativum) after infection with Erysiphe pisi

Qualitative and quantitative estimation of phenolic compounds was done through high performance liquid chromatography (HPLC) in different parts of pea ( Pisum sativum) after treatment with two plant growth-promoting rhizobacteria (PGPR), viz., Pseudomonas fluorescens (strain Pf4) and Pseudomonas aeruginosa (referred to here as Pag) and infection by Erysiphe pisi. The phenolic compounds detected were tannic, gallic, ferulic, and cinnamic acids on the basis of their retention time in HPLC. In all the treated plants, synthesis of phenolic compounds was enhanced. The induction of gallic, ferulic, and cinnamic acids was manyfold more than those in the control. Maximum accumulation of phenolic compounds was observed in plants raised from PGPR-treated seeds and infection with E. pisi. Under pathogenic stress, Pag performed better because a relatively higher amount of phenolics was induced compared with plants treated with Pf4.

Studies on exudate-depleted sclerotial development in Sclerotium rolfsii and the effect of oxalic acid, sclerotial exudate, and culture filtrate on phenolic acid induction in chickpea (Cicer arietinum)

Exudate depletion from developing sclerotia of Sclerotium rolfsii Sacc. in culture caused reduced size and weight of sclerotia. Germination of exudate-depleted sclerotia was delayed on Cyperus rotundus rhizome meal agar medium when compared with that of control sclerotia. The exudate-depleted sclerotia caused infection in chickpea (Cicer arietinum) plants in a glasshouse. Different temperatures and incubation periods had no effect on the germination ability of the exudate-depleted sclerotia. Oxalic acid, sclerotial exudate, and culture filtrate of S. rolfsii induced the synthesis of phenolic acids, including gallic, ferulic, chlorogenic, and cinnamic acids, as well as salicylic acid, in treated chickpea leaves. Gallic acid content was increased in treated leaves compared with the untreated controls. Maximum induction of gallic acid was seen in both leaves treated with oxalic acid followed by exudate and leaves treated with culture filtrate. Cinnamic and salicylic acids were not induced in exudate-treated leaves. Ethyl acetate fractionation indicated that the sclerotial exudates consisted of gallic, oxalic, ferulic, chlorogenic, and cinnamic acids, whereas the culture filtrate consisted of gallic, oxalic, and cinnamic acids along with many other unidentified compounds.

Role of garlic (Allium sativum L.) in human and plant diseases

A resurgence of interest in garlic due to recent revelations of its beneficial effects in the treatment of various human and plant diseases and also due to validation of claims made in traditional systems of medicine has resulted a plethora of publications on different aspects of garlic in recent years. Chemical constituents of garlic and their variations on the methods of isolation have been discussed in the present review. Effect of garlic and its constituents against various human and plant pathogenic and saprophytic microorganisms has also been reviewed.

Effect of calcium and calmodulin modulators on the development of Erysiphe pisi on pea leaves

The effect of calcium and calmodulin modulators, viz., ethylene glycol bis (beta-amino ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), a calcium chelator; verapamil, a plasma membrane Ca2+ channel blocker; ruthenium red, an organelle Ca2+ channel blocker; and chlorpromazine, a calmodulin antagonist; on the development of Erysiphe pisi was studied by floating the inoculated leaves on the respective solutions of chemicals. All the modulators affected the development of E. pisi by inhibiting the colony diameter, number of secondary branches, number of hyphal cells per colony and number of haustoria. The calmodulin antagonist was more effective in reducing E. pisi development. The results suggest the possible involvement of calcium and calmodulin in the development of E. pisi on pea leaves.

Antifungal activity of venenatine, an indole alkaloid isolated from Alstonia venenata

The indole alkaloid venenatine exhibited antifungal activity against some plant pathogenic and saprophytic fungi. Venenatine in an aqueous acetic acid solution inhibited spore germination of all the 10 tested fungi, Fusarium udum, Alternaria brassicicola, Ustilago cynodontis and Aspergillus flavus showed an especially high sensitivity towards this compound, exhibiting germination levels below 10%. The spore germination and colony development of the parasitic fungus Erysiphe pisi, which causes powdery mildew in pea (Pisum sativum), on excised leaves of pea was also significantly affected. Pre-inoculation rather than post inoculation treatment of the leaves was more inhibitory against spore germination and colony development.

A novel technique to measure the group velocity of sound in dispersive media

A technique is proposed for measuring the group velocity of sound by a frequency-modulated (FM) continuous wave (CW) technique. Detailed calculations are presented, showing that V(g)=(deltaomega(m)/deltaphi)d , where V(g), deltaomega(m), deltaphi, and d are, respectively, the group velocity, change of modulation frequency, phase change of the received signal detected by a biphase lock-in amplifier, and the distance traveled by the sound. The approach has the advantage of high resolution compared to the conventional time-of-flight measurement technique.