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White mold and stem rot is a common disease of Phaseolus vulgaris caused by Sclerotinia sclerotiorum. Biological control is a promising alternative for the control of this disease. In the present study, two Trichoderma spp., T. erinaceum and T. viride, and the consortium of both were evaluated as biocontrol agents against sclerotinia stem rot disease. The results revealed that T. erinaceum (NAIMCC-F-02171) and T. viride (NAIMCC-F-02500) when applied alone, significantly suppressed the infection rate of S. sclerotiorum and increased the rate of survival of plants by 74.5%. On the contrary, the combination of both the Trichoderma spp. was found to be more effective in reducing stem rot by 57.2% and increasing the survival of plants by 87.5% when compared to the individual Trichoderma applications. Further, the exogenous supplementation of Trichoderma activated antioxidative machineries, such as peroxidase, polyphenol oxidase, superoxide dismutase, catalase, and ascorbic acid in the plant. Besides, hydrogen peroxide and superoxide-free radical accumulation were also found to be reduced when T. erinaceum and T. viride were used either individually or in combination under the pathogen-challenged condition. Additionally, the photopigments in the bioprimed plants were markedly increased. Moreover, the combined inoculation of the two isolates yielded the highest records of growth parameters (root weight, shoot length, and leaf weight) compared with individual inoculation. Therefore, based on the above results, it was concluded that the combination of T. erinaceum and T. viride can be effectively used as an alternative to control white mold and stem rot caused by S. sclerotiorum.

Postemergence damping‐off of chilli caused by Pythium spp. is a common and serious problem in large chilli growing areas of India under the moist conditions that generally prevails during the sowing period. Therefore, in order to better understand this disease, an isolate belonging to the genus Pythium (Pythiales) was isolated from the infected chilli (Capsicum annuum L.) plant root parts collected from the fields of Chandauli district, Uttar Pradesh, India. Based on the congruence of cultural, morphological, cardinal growth rate and the sequence data analysis, the isolate was identified as Pythium graminicola. The molecular phylogenetic analysis based on ITS‐rDNA sequences clustered the isolate with representative sequences for P. graminicola from GenBank in the Pythium clade. The isolate carbon utilization profiles were characterized using Biolog FF MicroPlate method. The results revealed that the isolate used a wide range of carbon sources, mainly carbohydrates, but also amino acids, suggesting the use of metabolic routes that include glycolysis/gluconeogenesis. Moreover, an in vitro colony growth inhibition assay was performed to determine the influence of chemical (fungicides) and biological (bacteria and fungi) antagonists over the pathogen using the poison plate and dual culture method, respectively. Overall, the results revealed that the presence of aggressive broad range biocontrol agents can be used as an effective environmentally friendly approach for management and control of damping‐off in production systems. The antagonist can serve as a bio‐efficient and eco‐friendly alternative to synthetic fungicides for the development of an effective integrated pest management (IPM) system and obtaining higher yields.

Trichodrema is considered to be the most beneficial fungal genus for protecting crops in organic systems. The present study focuses on isolation, screening and identification of salinity tolerant T...

In the present study, Paenibacillus dendritiformis, Trichoderma harzianum, and Trichoderma asperellum were appraised as potential biocontrol agents that induce resistance in chilli (Capsicum annuum) against the devastating pathogen Colletotrichum truncatum, which causes anthracnose. Bright-field and scanning electron micrographs showed the hyphal degradation, lysis, and abnormal swelling in C. truncatum against P. dendritiformis in a dual plate assay. Under greenhouse conditions, chilli seeds pretreated with P. dendritiformis, T. asperellum, T. harzianum, and T. asperellum + T. harzianum by soil soak method inflicted an induced systemic resistance (ISR) in chilli against a C. truncatum-challenged condition. In chilli, the disease index percentage was significantly reduced in the T. asperellum + T. harzianum-treated seeds, followed by the T. harzianum-, T. asperellum-, and P. dendritiformis-treated seeds as compared to the untreated and challenged, respectively. Chilli seeds were primed with T. asperellum + T. harzianum (78.67%), which revealed maximum disease protection under the challenged condition, followed by T. harzianum (70%), T. asperellum (64%), and P. dendritiformis (56%) as compared to untreated and C. truncatum-challenged (6%) condition served as control. The seeds that were pretreated with biocontrol agents (BCAs) inflicted ISR against C. truncatum by enhancing the activity of defence-related enzymes (superoxide dismutase (SOD), peroxidase (POX), polyphenol oxidase (PPO), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and phenylalanine ammonia-lyase (PAL)), accumulating phenolic compounds, and increasing the relative chlorophyll content in chilli. Nitroblue tetrazolium (NBT) and 3,3′-Diaminobenzidine (DAB) stains were used to detect the accumulation of superoxide anion and hydrogen peroxide that appeared nearby the fungal infection sites. The accumulation of reactive oxygen species (O2− and H2O2) in the pathogen-inoculated leaves was a maximum of 48 hpi, followed by P. dendritiformis, T. asperellum, T. harzianum, and T. asperellum + T. harzianum treated tissue upon C. truncatum-challenged condition as compared to the control. Overall, our results showed the potential of T. harzianum, T. asperellum, and P. dendritiformis as biocontrol agents that prevent infection by C. truncatum and inflict an induced systemic resistance in chilli by enhancing the biosynthesis of phenolic compounds, defence and antioxidative enzymes, and reducing the lesiondevelopment and reactive oxygen species accumulation. This is the first report of induced systemic resistance against anthracnose in chilli obtained by application of T. harzianum, T. asperellum and P. dendritiformis, through seed priming.

Global food security is the major concern for farmers and agricultural scientists. With the rapidly rising population, developing technological innovations, decreasing land resources, and excessive consumption of nonrenewable resources, in order to increase agricultural production puts severe constraints on the vegetated agroecosystem. Use of chemical fertilizers and other agrochemical inputs have environmental concerns and could have severe effects on human health. In this context, we need to search for and develop an alternative platform for raising productivity, and therefore assure nutritional security for the future population. The plant microbiome constitutes the host-associated (epiphytic, endophytic, phyllospheric, and/or rhizospheric) microbial communities, and their interplay in mediating the functional interaction between different parts of the host, and other soil microbes. Soil microbes have extreme potential for plant growth and development and possess plant growth promotion characteristics. These microbes could improve plant productivity through a plethora of mechanisms, like phosphate solubilization, siderophore production, solubilization and mobilization of mineral nutrients, nutrient uptake, nutrient cycling, biological nitrogen fixation, phytohormone production, disease suppression, production of bioactive metabolites, biodegradation, biotransformation, defense-related hydrolytic activity, biological control, rhizomediation, and resistance against abiotic and biotic stresses. Studying the beneficial aspects of microbes in plant growth, and metabolism would be useful in developing microbial formulations or microbial consortia for agricultural biotechnology, and therefore improving the agricultural productivity through low-cost sustainable technology.

Several soilborne plant pathogens pose serious threat tocrop production across the globe. In order to increase crop productivity, farmers have indiscriminately used chemical pesticides that have caused adverse effects tohuman health, animals, and the environment. Among the various pesticides used, fungicides comprisethe major share worldwide; most of the crop loss is due to fungal diseases. In order to manage these diseases, several biocontrol agents are now being used as an alternative tothese synthetic pesticides. For a biocontrol agent to be successful, its biomass should be of high population count and with a level of viability and vigor. So, in order to increase the efficacy of biocontrol agents, a nanoparticle (NP) based strategy has now been adopted. NPs have gained importance in the agriculture sector because of their high stability;they are also non-toxic, cost-effective, and eco-friendly to nature,compared to biopesticides. Green synthesis of nanoparticles has an increasing benefit because of the rising need for developing environmentally friendly, cost-effective, and safe strategies for nanomaterial synthesis. The biological methods of nanoparticle synthesis help in elimination of harsh processing conditions by enabling the synthesis ofphysiological pH, temperature, pressure, and they lower costsat the same time. Use of microorganisms for the synthesis of nanoparticles is a fairly new and exciting area of research with lots of potential for further development. Biopesticides are engineered as nanomaterials by exploiting the potential of biofungicides to conjugate with nanobased products forming covalent bonds. Trichoderma strains have for a timebeen used to control plant disease by mechanisms including antibiosis, parasitism, inducing host-plant resistance, and competition. Trichoderma is a filamentous fungus and is capable of extracellular synthesis of metal nanoparticles, and it also serves diverse functions from antibacterial activity to anticancer properties. The metal NPs synthesized through this biosystems approach are very stable for a long period of time and have been reported to have a significant growth-inhibiting effect against various species of Fusarium, Helminthosporium, Penicillium, Pyricularia, Sclerotinia etc.

Plant growth-promoting rhizobacteria (PGPR) are diverse groups of plant-associated microorganisms, which can reduce the severity or incidence of disease during antagonism among bacteria and soil-borne pathogens, as well as by influencing a systemic resistance to elicit defense response in host plants. An amalgamation of various strains of PGPR has improved the efficacy by enhancing the systemic resistance opposed to various pathogens affecting the crop. Many PGPR used with seed treatment causes structural improvement of the cell wall and physiological/biochemical changes leading to the synthesis of proteins, peptides, and chemicals occupied in plant defense mechanisms. The major determinants of PGPR-mediated induced systemic resistance (ISR) are lipopolysaccharides, lipopeptides, siderophores, pyocyanin, antibiotics 2,4-diacetylphoroglucinol, the volatile 2,3-butanediol, N-alkylated benzylamine, and iron-regulated compounds. Many PGPR inoculants have been commercialized and these inoculants consequently aid in the improvement of crop growth yield and provide effective reinforcement to the crop from disease, whereas other inoculants are used as biofertilizers for native as well as crops growing at diverse extreme habitat and exhibit multifunctional plant growth-promoting attributes. A number of applications of PGPR formulation are needed to maintain the resistance levels in crop plants. Several microarray-based studies have been done to identify the genes, which are associated with PGPR-induced systemic resistance. Identification of these genes associated with ISR-mediating disease suppression and biochemical changes in the crop plant is one of the essential steps in understanding the disease resistance mechanisms in crops. Therefore, in this review, we discuss the PGPR-mediated innovative methods, focusing on the mode of action of compounds authorized that may be significant in the development contributing to enhance plant growth, disease resistance, and serve as an efficient bioinoculants for sustainable agriculture. The review also highlights current research progress in this field with a special emphasis on challenges, limitations, and their environmental and economic advantages.

Endophyte is defined as an important group of widespread and diverse plant symbionts that live asymptomatically and sometimes systematically within plant tissues without any harm or causing diseases in host plants. Fungal endophytes establish a beneficial symbiotic relationship with host plants and have been demonstrated to have high impact on host plants. The association of fungal communities with their host plants improves growth, immunity, and overall developments of plants. The fungal endophytes have been reported for unrevealing benefits to their host plants including plant growth promotion, production of secondary metabolites, and other bioactive compounds, amelioration of various abiotic and biotic stresses, improving agricultural productivity, providing disease resistance against dreadful phytopathogens, all of which promotes the crop production through sustainable approaches. Further, the investigation of defensive mechanism provided by these fungal communities would be helpful in their utilization at commercial scale for bio-formulations. Endophytic fungus represents formerly uncharted fungal lineages and comprises vast amounts of fungal diversity in associated plants Therefore, there is a high probability of discovering potential endophytic fungi with major application in all sectors including agriculture, therapeutic, and for commercial exploitation.

Rice is a staple food of more than half of the world’s population; more than 3.5 billion inhabitants depend on rice for obtaining 20% of their daily calorie intake. Nitrogen is the most important for crop growth and yield potential. Indeed, nitrogen is essential to stimulate tillering, leaf growth, photosynthesis, and protein synthesis. Significant achievements have recently been observed at the molecular level in nitrogen use efficiency and water use efficiency in plants. In this chapter we will discuss the following issue: (i) definition of both nitrogen use efficiency and water use efficiency, (ii) genes responsible for nitrogen use efficiency and water use efficiency, (iii) best ways for improving water and nutrient use efficiency in rice, and (iv) optimizing nitrogen options for improving water and nitrogen use efficiency of rice under different water regimes.

In context to sustainable agriculture practices, the agro-ecological system aims at optimizing the economic and environmental performances of beneficial ecosystem services to optimize the agricultural food production for future growing population, preserving the natural resources. The synthetic chemicals used in the agriculture to increase yields, kill pathogens, pests, and weeds have a big harmful impact on the ecosystem. Biostimulants can be used as a tool to complement the use of chemical inputs, by involving nonliving-based products, or living-based products, containing beneficial rhizosphere microbiome, such as plant growth-promoting rhizobacteria and beneficial fungi. Increase in soil fertility, plant growth promotion, and suppression of phytopathogens are the targets of the bioformulation industry that leads to the development of ecofriendly environment. Pest management research has also made major advances in the development of efficient biocontrol methods. Elicitors and semiochemicals are considered to be some of the most promising tools for inducing plant resistance to various diseases and enhancing natural predation, respectively. Bioformulations offer an environmentally sustainable approach to increase crop production and health, contributing substantially in making the 21st century the age of biotechnology.

The rhizosphere is the zone under influence of plant roots where various kinds of microbial activities occur which perform important functions such as increase uptake of nutrients for the host for their better growth and protection from several diseases caused by various phytopathogens. Keeping in this vital role performed by rhizospheric microbes, thirty-nine bacterial isolates were isolated on King's B and nutrient agar media from the rhizosphere region of mung bean plants. Among these isolates, foure were identified as Pseudomonas spp., Bacillus sp., Acinetobacter sp. on the basis of biochemical and 16 S rDNA gene sequencing analysis. All the isolates were screened in vitro for plant growth promoting attributes such as IAA production, phosphate solubilization, ammonia production, catalase production, siderophore production, and antagonistic activity against phytopathogenic Rhizoctonia solani, the causal organism of root rot in mung bean. All the bacterial strains showed significant PGPR attributes and were able to produce indole-3 -acetic acid (ranging from 45.66 µg/ml to 111.94 µg/ml). In addition, the isolated strains enhanced phosphate solubilization activity (ranging from 952.91 µg/ml to 1341.24 µg/ml). Out of all, Pseudomonas spp. showed most potent antifungal activities against R. solani. Thus, the current study has focused on the characterization of rhizobacteria isolated from the rhizosphere of healthy mung bean plant. The results showed that the isolates posses, multiple plant growth-promoting (PGP) traits and can be used as a potential candidate on the soil-plant system to increase their growth as well as productivity.

Plant growth-promoting rhizobacteria (PGPR) are beneficial rhizosphere derived bacteria that have the capability to colonize plant roots and are used to enhance plant growth or suppress disease caused by various phytopathogens. The fourteen isolates were screened on the basis of in vitro antagonistic activity against the root rot pathogen Rhizoctonia solani but in the present study, we have selected, two strains of rhizobacteria (Pseudomonas aeruginosa BHU B13-398 and Bacillus subtilis BHU M) through initial screening as well as their in vitro antagonistic potential activity against the root rot pathogen Rhizoctonia solani. These isolates were then tested in vitro for their specific PGPR traits, such as phosphate solubilization, ammonia, siderophore and HCN production. Both the isolates were found to be promising agents for all the tested PGPR traits. Among the two isolates, BHU B13-398 showed highest plant growth promoting attributes. Pot experiments were conducted on mung bean to evaluate their plant growth promotion potential under the controlled green house conditions (14 h light, 10 h dark, and temperature at 27 ± 2 °C). The results revealed that both the isolates (BHU B13-398 and BHU M) enhanced the growth parameters of mung bean such as root length, shoot length, root as well as shoot fresh and dry weight, leaf area and chlorophyll content compared to uninoculated control plants. Our results clearly demonstrated that both the isolates BHU B13-398 and BHU M displayed 32.26%, 84.60% and 13.38%, 61.94%, increase in shoot length, and root length respectively, as compared to uninoculated control. Mung bean root sections inoculated with respective strains were observed through scanning electron microscopy (SEM) to validate mung bean root colonizing abilities of the strains. The SEM observation confirmed that both strains BHU B13-398 and BHU M seem to be a good root colonizer and have high population densities on the root surface.

Cadmium (Cd) is a non essential and toxic heavy metal that gets incorporated in the soil ecosystem through several anthropogenic activities. The Cd contaminated soils might have devastating affects on seed germination, plant growth and development. In the present work, a comparative evaluation was made to determine and optimize the detrimental level of accumulated toxic Cd metal in the tomato (Solanum lycopersicum; CO-3 variety). The perturbed morpho-physiological, biochemical alterations and molecular responses following the Cd induced stress were found to maximum at 250 μM Cd with having the highest expression of LeNRAMP3 gene. The oxidative burst induced and cell death was visualized through histochemical analysis using Evans blue (cell death) and DAB staining (H2O2 accumulation). The structural modelling of metal transporter protein done through homology modelling was found to acquire typical helical configuration, and revealed the potential active site residues involved in metal chelation. The function of LeNRAMP3 was deduced based on the functional annotation of protein AtNRAMP3. The functional signaling network and evolutionary relationships for LeNRAMP3 were explored and predicted based on comparative genomics and proteomic studies using the interactome pathways available for AtNRAMP3. The study revealed that LeNRAMP3 metal transporters are activily involved in Cd translocation from root to leaves of tomato and sensitive at 250 μM Cd concentration in the tomato plants.

Trichoderma spp. are well-known biological agents that have significant antagonistic activity against several plant pathogenic fungi. In the present study, Trichoderma spp. were tested in vitro for...

The use of soil bioagent along with chemical inducers in controlling plant diseases is a unique strategy. The exogenous application of some chemical inducers such as salicylic acid (SA) or methyl jasmonate (MeJA) provides resistance to combat plant pathogens. The intrinsic mechanism that leads into the enhanced defense mechanism by using biological microorganisms, however, correlates with the signaling pathways involving these chemical inducers. In the present study, we have evaluated the biochemical changes relevant to defense activities when plants were pretreated with bioagent, Trichoderma harzianum (Th) and chemical inducers (SA and/or MeJA) and challenged by wilt pathogen Fusarium oxysporum f. sp. lycopersici. We have also evaluated the combined effect of biological (Th) and chemical inducers (SA and/or MeJA) pretreatment followed by pathogen exposure on the biochemical defense-related parameters in tomato. We found that the combined application of Trichoderma along with SA and MeJA provided a better strategy for controlling wilt pathogen rather than using bioagent and chemical inducers alone. The defense-related proteins and phenolics were found to be increased several folds at different time intervals following the combined treatment of biological and chemical inducers compared to when treatment was given alone with bioagent and chemical inducers. The activation of the phenylpropanoid pathway and accumulation of total phenolics were found to be highest at 48 h, whereas the activities of defense-related enzymes and PR proteins along with proline, were found to be maximum at 72 h. The activities of phenolics were also maximum at 48 h, and the activities of PR proteins and proline were higher at 72 h in all single treatments. However, the defense-related activities were greater in combined treatment compared to all single pretreated samples. Therefore, the combined pretreatment with bioagent and chemical inducers triggered the more aggressive defense responses when compared to single treatments and provided better protection against Fusarium wilt.

Tomato is considered as one of the most important sources of nutrients such as lycopene, β-carotene, flavonoids, ascorbic acid (vitamin C) and hydroxyl-cinnamic acid derivatives. The quality and quantity of nutrients in tomato fruits were decreased during the severe infection of Alternaria alternata. The present study deals with the estimation of lycopene, β-carotene, phenolic and ascorbic acid content in tomato fruits which were infected with A. alternata and its toxins such as tenuazonic acid (TeA), alternariol (AOH) and alternariol monomethyl ether (AME). The lycopene, β-carotene, ascorbic acid and phenolic content were found lowest in pathogen-infected fruits i.e. (0.66 ± 0.03 mg/g), (0.14 ± 0.01 mg/g), (1.89 ± 0.2 mg/g) and (0.58 ± 0.05 mg/g), respectively, followed by toxins-treated samples as compared to the control. The results concluded that A. alternata mostly affects the nutritional values of tomato fruits due to the combined effect of the toxins.

For over a century, chemical control of pests is a common practice in agriculture. The average reduction in global crop loss due to use of pesticides is around ∼39%. The postharvest losses and quality decline caused by storage pests are major problems in a subtropical country like India. So, the farmers have relied heavily on the use of chemical pesticides to improve their crop production, which is now paying a huge toll on the human health and environment. Though the chemical pesticides are very effective, what concerns over their use is their effect on soil and environment and presence of residue in food products. Another major issue is the development of resistance in the pests. Therefore, the use of biopesticides to control pests is now preferred over synthetic pesticides because of their pest control ability and diverse mode of actions which helps in avoiding resistance development in the pests. In a country like India with a huge diversity of plants, there is an urgent need for identifying new biopesticides which can serve the purpose of pest control. India needs to develop its own biocontrol agents (BCA) because it will be cost-effective and also environment-friendly. Major hurdle in the development and use of new biopesticides in India is the commercialization process. The farmers are reluctant to use the new products because of high cost and no practical knowledge.

Background In response to various environmental stresses, many plant species synthesize L-proline in the cytosol and accumulates in the chloroplasts. L-Proline accumulation in plants is a well-recognized physiological reaction to osmotic stress prompted by salinity, drought and other abiotic stresses. L-Proline plays several protective functions such as osmoprotectant, stabilizing cellular structures, enzymes, and scavenging reactive oxygen species (ROS), and keeps up redox balance in adverse situations. In addition, ample-studied osmoprotective capacity, L-proline has been also ensnared in the regulation of plant improvement, including flowering, pollen, embryo, and leaf enlargement. Scope and conclusions Albeit, ample is now well-known about L-proline metabolism, but certain characteristics of its biological roles are still indistinct. In the present review, we discuss the L-proline accumulation, metabolism, signaling, transport and regulation in the plants. We also discuss the effects of exogenous L-proline during different environmental conditions. L-Proline biosynthesis and catabolism are controlled by several cellular mechanisms, of which we identify only very fewer mechanisms. So, in the future, there is a requirement to identify such types of cellular mechanisms., L-Proline; Osmoprotectant; Environmental stresses; Cellular mechanisms; Signal transduction, Biochemistry, Molecular biology, Cell Biology, Plant Biology.

Plant growth and development are greatly affected by various biotic and abiotic stresses. Various strategies are utilized to minimize stresses in plants. Seed priming with beneficial microorganisms is one of the most beneficial methods to improve plant growth and development and induce systemic tolerance in plants towards biotic as well as abiotic stresses. Seed priming is a method of conditioning the seeds by plant growth-promoting microbes which provide better abilities to the plant to withstand various environmental challenges beginning from seed germination. Seed priming with beneficial microorganism is also known as bio-priming that enhances seed germination, protects germinating seed from different phytopathogens, and provides suitable conditions for establishment of the plant. Bio-priming has several mechanisms to stimulate morphogenesis and plant immunity, viz., production of phytohormones, induced expression of plant growth-promoting genes, increased nutrient status into the plant, mycoparasitism, antibiosis, induced phenolic production, activation of antioxidant production, and systemic defense activation. Some important microorganisms that synthesize phytohormones include Azotobacter spp., Pantoea agglomerans, Rhodospirillum rubrum, Rhizobium spp., Bacillus subtilis, Pseudomonas fluorescens, Paenibacillus polymyxa, Trichoderma spp., Pseudomonas putida, Rhizobium phaseoli, Bacillus cereus, and Acinetobacter calcoaceticus. The main objective of this chapter is to enlighten the importance of seed priming with microorganisms and the role of different phytohormones produced by them in modulating growth, development, and defense activation in the host plant.

Plant defense against their pathogens can be induced by a complex network of different inducers. The present study investigates the synergistic effect of Trichoderma harzianum, exogenous salicylic acid (SA) and methyl jasmonate (MeJA) over the response and regulation of the antioxidant defense mechanisms and lipid peroxidation in tomato plants against Fusarium wilt disease. In the present work, tomato plants were infected by Fusarium oxysporum f. sp. lycopersici 3 days after inoculated with T. harzianum and/or sprayed daily for 3 days with chemical inducers (SA and MeJA). Plants were analysed at 0, 24, 48, 72 and 96 h after inoculation with Fusarium oxysporum f. sp. lycopersici. Infection of tomato plants by pathogen led to strong reduction in the dry weight of roots and shoots with the enhanced concentration of H2O2 and varying degree of lipid peroxidation. Concurrently, exogenous SA, when applied with pathogen greatly enhanced H2O2 content as well as activities of antioxidant enzymes except catalase (CAT) and ascorbate peroxidase (APx). The pathogen challenged plants pretreated with T. harzianum and MeJA together exhibited less lipid peroxidation and as well as the elevated level of ascorbic acid and enhanced activities of antioxidant enzymes. All applied treatments protected tomato seedlings against Fusarium wilt disease but the percentage of protection was found higher in plants pretreated with the combination of T. harzianum and chemical inducers.

Alternaria species produce various sorts of toxic metabolites during their active growth and causes severe diseases in many plants by limiting their productivity. These toxic metabolites incorporate various mycotoxins comprising of dibenzo-α-pyrone and some tetramic acid derivatives. In this study, we have screened out total 48 isolates of Alternaria from different plants belonging to different locations in India, on the basis of their pathogenic nature. Pathogenicity testing of these 48 strains on susceptible tomato variety (CO-3) showed 27.08% of the strains were highly pathogenic, 35.41% moderately pathogenic and 37.5% were less pathogenic. Phylogenetic analysis showed the presence of at least eight evolutionary cluster of the pathogen. Toxins (TeA, AOH and AME) were isolated, purified on the basis of column chromatography and TLC, and further confirmed by the HPLC-UV chromatograms using standards. The final detection of toxins was done by the LC-MS/MS analysis by their mass/charge ratio. The present study develops an approach to classify the toxicogenic effect of each of the individual mycotoxins on tomato plant and focuses their differential susceptibility to develop disease symptoms. This study represents the report of the natural occurrence and distribution of Alternaria toxins in various plants from India.

Plant signalling 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 (STK) 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.

Fusarium wilt is one of the most prevalent and damaging diseases of tomato. Among various toxins secreted by the Fusarium oxysporum f. sp. lycopersici (causal agent of Fusarium wilt of tomato), fusaric acid (FA) is suspected to be a potent pathogenicity factor in tomato wilt disease development. With this rationale the present study was carried out with physiological, biochemical and proteomic perspectives. Treatment of FA was given to the leaves of tomato directly through infiltration to show the characteristic features of Fusarium wilt of tomato. The phytotoxic effect of FA was assessed in the form of cell death in tomato leaves which was observed by increased uptake of Evans blue stain. The measurement of electrolyte leakage was used as an indicator of the extent of cell death. The influence of FA on the leaf photosynthesis of tomato plant was investigated and it was found that FA strongly reduced the photosynthetic pigment contents of tomato leaves resulting to heavy suppression of leaf photosynthesis processes, which therefore affected leaf physiology finally leading to leaf wilting and necrosis. This cell death inducer (FA) produced an enormous oxidative burst during which large quantities of reactive oxygen species (ROS) like H2O2 was generated in the treated leaf tissues of tomato plants which was evident from enhancement in lipid peroxidation. To assess the involvement of proteolysis in the cell death cascade induced by FA treatment, total protease activity was measured in the leaf tissues and it was found that the total protease activity increased with the treatment and leading to cell death. Furthermore, proteomic study was used as a powerful tool to understand the alterations in cellular protein expression in response to FA exposure. Differential expression in several proteins was observed in the present study. Proteomic analyses, thus, clearly indicate that proteins belonging to different functional classes are significantly affected in the plant leaf tissues after FA exposure leading to deterioration of structure and metabolism of cells. Thus, it is concluded that FA plays an important role in fungal pathogenicity by decreasing cell viability.

Plant growth-promoting microorganisms (PGPMs) constitute the microbes that are intricately associated with the plant system and may consist of rhizospheric bacteria, fungi, mycorrhiza, endophytic fungi, actinomycetes, or those having the mutualistic relationship or nonsymbiotic relationship with plants. One of the most remarkable features of these microbes is the adoption of certain ecological niches or may be occupied with multiple niches at a time in the soil ecosystem that makes way for other species to establish the mutual interactions (physical or biochemical) with other microbes (bipartite) or with plants (tripartite). The plant growth promotion by these microbes involves common mechanisms such as nitrogen fixation, siderophore production, phytohormone production, solubilization of mineral phosphates and secretion of novel secondary metabolites having positive effect on plant health. Some beneficial fungi have been found to promote plant growth through increased photosynthetic rate with improved mineral use efficiency and nutrient uptake, as inoculating these microbes with plants lead into increased chlorophyll content and biomass. These indigenous microbes have been also reported to counteract the different abiotic and biotic stress conditions. The mutual interaction observed between beneficial fungi and pathogenic microbes has been investigated at microscopic level which involves certain physical changes such as coiling of beneficial hyphae around the pathogenic hyphae and some cellular changes such as dissolution of host cytoplasm or secretion of antimicrobial compounds or lytic enzymes in the nearby localities that check the growth and reproduction of pathogenic species. The comprehensive knowledge of the functional mechanism of plant growth promotion by these microbes will help to develop strategies against damages covered by various abiotic and biotic stress conditions, and therefore will help in increasing the agricultural production at a global scale.

In this study, the generation of reactive oxygen species, the induction of oxidative stress, and the response of the antioxidative system in hydroponically grown tomato plants as the cause of arsenic-induced phytotoxicity are investigated. Reduction in plant growth was measured in terms of dry weight and length of roots and shoots, the latter accumulating more arsenic than the roots. The treatment resulted in increased formation of superoxide anion (O2.−), H2O2, and thiobarbituric acid reactive substances, which indicate augmented lipid peroxidation. Superoxide dismutase, catalase (CAT), and ascorbate peroxidase activities were increased in arsenic-treated tomato plants while CAT activity was insignificantly increased.

Rhizosphere microbe-mediated induction of antioxidant mechanisms for disease resistance in plants is known but their impact on nutritional content of the edible parts is not clear. A study was conducted to evaluate potentiality of three compatible rhizosphere microbes, viz., fluorescent Pseudomonas (PHU 094), Trichoderma harzianum (THU 0816) and Mesorhizobium sp. (RL 091), singly and in combinations in modulating antioxidants in chickpea edible parts. Total phenolic and flavonoid content, ascorbic acid, free radical and hydroxyl radical scavenging activities as well as reducing power in seeds and pericarp in different microbial combinations were significantly high compared to their single application. However, the triple microbe treatment was most effective in enhancing the antioxidant status of chickpea along with enhanced accumulation of phenolics such as shikimic, gallic, tannic, p-coumaric, and ferulic acids as well as rutin and quercetin. Apart from the triple microbe treatment, dual combination of PHU 094 + THU 0816 also showed potentiality in enhancing the antioxidant and phenolic content majorly in pericarp. These findings suggest that synergistic interaction of microbes in the rhizosphere not only improved the antioxidant level in chickpea seeds but the same were also enhanced in the pericarp which is otherwise considered a waste material.

Various studies have been conducted recently using microalgal system for the production of algal lipid for biodiesel production. This study aimed at increasing the extraction efficiency of algal lipid from Chlorella sp. by the application of Chlorella viruses. The calorific value of lipid from Chlorella sp. has been reported to be higher than that of fresh water microalgae, making it a potential candidate to be used as biofuel. This is the first report on novel application of microalgal viruses for improving the extraction efficiency of algal lipid for biodiesel production through viral lysis of Chlorella vulgaris . The algal lipid extraction efficiency, increased by 11.68% in the case of Chlorella virus treated C. vulgaris when compared with Chlorella virus untreated C. vulgaris . The application of Chlorella virus and the viral encoded lytic enzymes for increasing the extraction efficiency of algal lipid will be helpful in optimizing algal biofuel industry in the future. Keywords: Micro-algal system, biodiesel, algal lipid, Chlorella viruses, viral lysis. African Journal of Biotechnology , Vol 13(15), 1666-1670

The field of allelopathy is one of the most fascinating but controversial processes in plant ecology that offers an exciting, interdisciplinary, complex, and challenging study. In spite of the established role of soil microbes in plant health, their role has also been consolidated in studies of allelopathy. Moreover, allelopathy can be better understood by incorporating soil microbial ecology that determines the relevance of allelopathy phenomenon. Therefore, while discussing the role of allelochemicals in plant-plant interactions, the dynamic nature of soil microbes should not be overlooked. The occurrence and toxicity of allelochemicals in soil depend on various factors, but the type of microflora in the surroundings plays a crucial role because it can interfere with its allelopathic nature. Such microbes could be of prime importance for biological control management of weeds reducing the cost and ill effects of chemical herbicides. Among microbes, our main focus is on bacteria--as they are dominant among other microbes and are being used for enhancing crop production for decades--and fungi. Hence, to refer to both bacteria and fungi, we have used the term microbes. This review discusses the beneficial role of microbes in reducing the allelopathic effects of weeds. The review is mainly focused on various functions of bacteria in (1) reducing allelopathic inhibition caused by weeds to reduce crop yield loss, (2) building inherent defense capacity in plants against allelopathic weed, and (3) deciphering beneficial rhizospheric process such as chemotaxis/biofilm, degradation of toxic allelochemicals, and induced gene expression.

The aim of this study was to evaluate the potentiality of three compatible rhizosphere microbes, viz. fluorescent Pseudomonas aeruginosa (PHU094), Trichoderma harzianum (THU0816) and Mesorhizobium sp. (RL091), in community to mobilise antioxidant mechanisms in chickpea under the challenge of Sclerotium rolfsii. The microbes were applied as seed treatment in different combinations in two sets and the pathogen was inoculated in one of the sets after 3weeks of sowing. A comparative study was conducted on the effect of the microbial combinations on host antioxidant mechanisms between the two sets. In pathogen challenged plants host defence responses included higher accumulation of hydrogen peroxide (H2O2) at petiolar and interveinal regions of leaf and high activities of catalase (CAT), glutathione reductase (GR) and guaiacol peroxidase (GPx) compared to unchallenged plants. The antioxidant enzyme activities increased 1.8−3.3 and 1.9−3.1 folds at 48 and 72h, respectively, in the triple microbe treated challenged plants compared to unchallenged ones. Although, ascorbate peroxidase (APX) activity was significantly low, ascorbic acid (AA) and chitinase accumulation was high in the pathogen challenged plants. Antioxidant flavonols associated with host defence namely myricetin, quercetin and kaempferol also accumulated in high amounts in pathogen challenged plants. Among the microbial treatments, the triple microbe combination induced the highest response in all parameters as compared to dual or single application of the same microbes. The triple microbe consortium modulated the chickpea antioxidant mechanisms more efficiently and modulation of oxidative stress was directly correlated with lower plant mortality, thus demonstrating the synergistic behaviour of the microbes in protecting chickpea from the pathogen.

The study was conducted to examine efficacy of a rhizospheric microbial consortium comprising of a fluorescent Pseudomonas (PHU094), Trichoderma (THU0816) and Rhizobium (RL091) strain on activation of physiological defense responses in chickpea against biotic stress caused by the collar rot pathogen Sclerotium rolfsii. Results of individual microbes were compared with dual and triple strain mixture treatments with reduced microbial load (1/2 and 1/3rd, respectively, of individual microbial load compared to single microbe application) in the mixtures. Periodical studies revealed maximum activities of phenylalanine ammonia lyase [E.C. 4.1.3.5] and polyphenol oxidase [E.C. 1.14.18.1] and accumulation of total phenol content in chickpea in the triple microbe consortium treated plants challenged with the pathogen compared to the single microbe and dual microbial consortia. Similarly, the expression of the antioxidant enzymes superoxide dismutase [E.C.1.15.1.1] and peroxidase [E.C.1.11.1.7] was also highest in the triple microbial consortium which was correlated with lesser lipid peroxidation in chickpea under the biotic stress. Histochemical staining clearly showed maximum and uniform lignification in vascular bundles of chickpea stem sections treated with the triple microbes. The physiological responses were directly correlated with the mortality rate as least plant mortality was recorded in the triple microbe consortium treated plants. The results thus suggest an augmented elicitation of stress response in chickpea under S. rolfsii stress by the triple microbial consortium in a synergistic manner under reduced microbial load.

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.

During the last two decades, there has been increasing interest in biodiesel as an alternative biofuel. Oleaginous fungi can represent a sustainable alternative to plant oil for the production of biodiesel and they can accumulate intracellular lipids up to 70 % under stress condition. Oleaginous fungi have given a new turn to fuel generation, as their lipids are rich in Tri-acyl glyceraldehydes (TAG) and specific polyunsaturated fatty acids (PUFA). With the increase in population, fuel production will be highly expensive and therefore a promising alternative is to look at microbial oil technology. This chapter focuses on the important fungi and enzymes involved in biofuel production and recent technologies for lipid extraction, which provide a platform for a viable and successful development in an industrial production process.

Whitefly (Bemisia tabaci) damages field crops by sucking sap and transmitting viral diseases. None of the insecticidal proteins used in genetically modified (GM) crop plants to date are effective against whitefly. We report the identification of a protein (Tma12) from an edible fern, Tectaria macrodonta (Fee) C. Chr., that is insecticidal to whitefly (median lethal concentration = 1.49 μg/ml in in vitro feeding assays) and interferes with its life cycle at sublethal doses. Transgenic cotton lines that express Tma12 at ∼0.01% of total soluble leaf protein were resistant to whitefly infestation in contained field trials, with no detectable yield penalty. The transgenic cotton lines were also protected from whitefly-borne cotton leaf curl viral disease. Rats fed Tma12 showed no detectable histological or biochemical changes, and this, together with the predicted absence of allergenic domains in Tma12, indicates that Tma12 might be well suited for deployment in GM crops to control whitefly and the viruses it carries.

In this study, the generation of reactive oxygen species, the induction of oxidative stress, and the response of the antioxidative system in hydroponically grown tomato plants as the cause of arsenic-induced phytotoxicity are investigated. Reduction in plant growth was measured in terms of dry weight and length of roots and shoots, the latter accumulating more arsenic than the roots. The treatment resulted in increased formation of superoxide anion (O2.−), H2O2, and thiobarbituric acid reactive substances, which indicate augmented lipid peroxidation. Superoxide dismutase, catalase (CAT), and ascorbate peroxidase activities were increased in arsenic-treated tomato plants while CAT activity was insignificantly increased.

The present study shows that vesicular-arbuscular mycorrhizal colonization in plants grown in saline-alkali soil is host dependent and it is significantly affected by various amendments given to reclaim such soils. Maximum reduction in vesicular-arbuscular mycorrhizal colonization was observed in the plants raised in saline-alkali soil amended with gypsum and maximum colonization was observed after plant-growth promoting rhizobacterium or farm yard manure amendments. Plants possessing high level of vesicular-arbuscular mycorrhizal colonization (50–70%) included Acacia nilotica, Albizia lebbeck and Dalbergia sissoo. Casuarina equisetifolia possessed moderate level of vesicular-arbuscular mycorrhizae colonization (30–50%) and Azadirachta indica possessed low level of colonization (20–40%).

Biological control of Fusarium udum causing wilt disease of pigeonpea was studied in vitro, as well as, in vivo. Aspergilluspavus, Anergillus niger, Bacilius licheniformis (strain-2042), Gliocladium virens, Peniciliium citrimum, and Trichoderma harzianum, which were found to be the most potent ones in inhibiting the radial colony growth of the test pathogen, were used as biological control by amending their inocula at diffeyent concentrations in pots and in pathogen-infested soil in the fields. Maximum reduction of the wilt disease was observed with G. vireos both in pots and in the fields. The population of E. udum was found to be markedly reduced when the antagonists were applied in the soil. The study establishes that G. virens can be exploited for the biological control of wilt disease at field level.

The present study was carried out to evaluate the biochemical changes occurring in tomato leaves following treatment with leaf spot disease causing pathogen Alternaria alternata and two of its phytotoxic metabolites. Results revealed that the pathogen treatment caused severe foliar necrosis and by 10th day of treatment almost 3/4th of the leaf area was necrotized. A significant decline in the chlorophyll content was observed in the leaves treated with the pathogen and its metabolites. Reducing sugars showed a visible decline in the treated leaves in comparison to the control leaves. When compared with the control an increase in total soluble protein was observed in leaves treated with the pathogen and its metabolites. In case of phenol, a significant enhancement in phenol content of the pathogen and metabolite treated leaves was observed than the amount detected in control leaves. The results indicate that infection of tomato by the leaf spot pathogen Alternaria alternata and its metabolites causes severe alterations in the amount of various biochemical components.

Traditional agricultural practices are getting severely hampered by multiple problems such as disease, pest, drought, salinity, decreased soil fertility because of the use of hazardous chemical pesticides and pollution. As a result, need of an hour is selection for some eco-friendly biocontrol agent that is a multitasker in terms of resolving the above mentioned problems. Trichoderma is one such genus that is ubiquitously present in the environment which has naturally sustained the agricultural yields and supported the human population over million years. They are known to produce different kinds of enzymes and elicit defense responses in plants which have a significant role in biotic and abiotic stress tolerance, hyphal growth as well as plant growth promotion. Trichoderma's mechanisms of antagonism and role in plant growth promotion have been well documented but fast paced current research utilizing all the “omics” in this field would actually unravel the hidden features of this fungus.

Some of the most potent toxins are synthesized by fungi. Fungal toxins are the chemicals produced by fungi under certain conditions. They may be classified under different chemical classes. They are not essential for fungal growth or reproduction, but are toxic to plants, animals or humans. Fungal toxin contamination in certain agricultural commodities has been a serious concern for animal and human health. The major toxin-producing fungi are the species of Aspergillus, Penicillium, Fusarium and Alternaria. Aflatoxins, citrinin, fumonisins, fusaric acid, moniliformin, AAL-toxins and alternariol are some of the important fungal toxins responsible for causing economic losses to agriculture, spoilage of food that are often fatal to living systems. This review focuses on toxigenic fungi, toxins and their characteristics with biological effects.

The comet assay is the widely used method for in vitro toxicity testing which is also an alternative to the use of animal models for in vivo testing. Since, its inception in 1984 by Ostling and Johansson, it is being modified frequently for a wide range of application. In spite of its wide applicability, unfortunately there is no report of its application in bacteriophages research. In this study, a novel application of comet assay for the detection of bacteriophage mediated bacterial cell lysis was described. The conventional methods in bacteriophage research for studying bacterial lysis by bacteriophages are plaque assay method. It is time consuming, laborious and costly. The lytic activity of bacteriophage devours the bacterial cell which results in the release of bacterial genomic material that gets detected by ethidium bromide staining method by the comet assay protocol. The objective of this study was to compare efficacy of comet assay with different assay used to study phage mediated bacterial lysis. The assay was performed on culture isolates (N = 80 studies), modified comet assay appear to have relatively higher sensitivity and specificity than other assay. The results of the study showed that the application of comet assay can be an economical, time saving and less laborious alternative to conventional plaque assay for the detection of bacteriophage mediated bacterial cell lysis.

Seed biopriming is an advance technique of seed treatment that involves application of beneficial microorganism on seed surface followed by seed hydration. Seed bioprimig is a ecological to control the many seed and soil-borne pathogens which provide an alternative to chemical treatment. Seed biopriming enhance the initial step of plant development by increased seed germination and provide protection before seedling emergence. Trichoderma spp. is widely used for biocontrol agent that enhance plant growth as well as inhibits phytopathogen. In the present study, effectiveness of biopriming with T. asperellum BHUT8 evaluated for plant growth promotion effect in pea. The results showed enhancement in plant growth in the treated plants as compared to control. There was increase in shoot length, root length, number of leaves, shoot fresh weight, root fresh weight, shoot dry weight and root dry weight by 35.29, 96.49, 28.13, 36.10, 146.26, 30.17 and 77.20%, respectively, as compared to the control.

Numerous toxic metals such as cadmium, selenium, lead, zinc etc. released from industrial production, mining, smelting and traffic contaminate the agricultural soils. This has raised concerns not only for crop quality but also for human health. Engineering and/or microbial based technologies are used to remove the toxic metals from contaminated soils. But these approaches are costly and less efficient in comparison to phytoremediation technique which has emerged as more efficient and cost effective method for decontamination of the toxic metal affected sites. There are highly specialized plants that have the ability to accumulate and tolerate high concentrations of toxic metals from soils and may provide the basis for remediation of heavy metal contaminated sites. Members of the family Brassicaceae have a key role in phytoremediation technology. Metal uptake, sensitivity and sequestration have been extensively investigated in Arabidopsis thaliana. There are a number of Brassica and related crop species that have been reported as the potential candidates for phytoremediation. Brassica spp. display a great diversity of morphological form and many are of economic value as oilseeds, vegetables and forages. They are well suited to genetic manipulation and in vitro culture techniques and are attractive candidates for the introduction of genes aimed at phytoremediation. Brassica oilseeds are adaptable to a range of environmental conditions. Moreover, rhizosphere of Brassica spp. is colonized by several beneficial microbes that can be isolated, mass cultured and utilized to maximize the biomass of this crop plant for use in phytoremediation technology. These microbial inoculants are cheaper as compared to the chemical fertilizers, and are not hazardous to the environment.

Publisher Summary It is clear from this chapter that bioremediation of toxic industrial effluents by micro-organisms can be an effective method for the removal of textile effluents, and can substitute the conventional remediation processes. Broad screening of microbial biomass type should be undertaken for developing new technologies. The current consensus is that, for improved commercial use of micro-organisms, immobilization or pellet preparations in suitable carriers will prove economical for their use. In relation to other parameters of industrial relevance, micro- organisms can be highly efficient in removing the toxic components from the effluents. The nonspecific lignin-degrading system of P. chrysosporium can be significantly utilized for the aerobic degradation of heterogeneous mixture of recalcitrant dyes in wastewaters. Growing evidence indicates that lignase (lignin peroxidase) is the key lignin-degrading enzyme of this whiterot fungus, which has potential for its commercial application.

Herbal medicines are of great importance in the primary healthcare of mankind in many developing countries. An ethno medicinal survey was undertaken through frequent field trips, interviews and discussions to collect information on the use of medicinal plants by native nomadic tribes in Pir Panjal Foothills of Kashmir Himalayas in 2009–2010. The investigation revealed that the traditional healers have been using twenty one species of medicinal plants belonging to twenty genera and nineteen families to treat various health problems. The documented medicinal plants were mostly used to cure skin diseases, diabetes, leprosy, ulcers, tumors, dysentery, diarrohea, typhoid, bronchitis, jaundice, small-pox, respiratory and eye infections. Many of these plants have been found to be very affective against several diseases and therefore, are of great medicinal value. These indigenous medicinal plants need to be studied and documented in the face of emerging threats of climate change, habitat degradation, over harvesting and bio-piracy.

The fungi in root regions of healthy and diseased Cajanus cajan differed qualitatively and quantitatively. F. udum was always recorded on the rhizoplane of wilted plants and about 90% of the total fungal population of the rhizosphere of wilted plants was F. udum. Due to such heavy infestation of F. udum the population of actinomycetes was suppressed in rhizosphere of the wilted plants. No definite pattern of increase or decrease in the population of bacteria was observed in root regions of healthy and diseased hosts. However, there were less in non-rhizosphere soil as compared with the rhizospheres. There was, in the beginning, a marked difference in succession of fungi in the rhizosphere and rhizoplane regions of excised healthy and wilted pigeon-pea roots. In early stages the population of F. udum decreased on decaying roots of the wilted plants but increased on that of the healthy ones. The number of fungi g−1 dry soil as well as the population of F. udum decreased on decaying roots of healthy and wilted plants both as natural senescence and decomposition progressed. In advanced stages of root decomposition the pattern of colonization and succession was similar on both types of the roots.

The interrelationship between the growth ofCoprinus lagopus andFusarium udum on pigeon pea substrates in soil was studied at 22-2°C and 30±2°C in relation to their competitive saprophytic ability and antagonism.C. lagopus was observed to be a potent and frequent colonizer of pigeon pea substrates in soil along withF. udum. Saprophytic colonization of pigeon pea substrate byF. udum precolonized byC. lagopus was inhibited in all inoculum soil mixtures. Saprophytic colonization of the substrate byF. udum was better at 22°C than at 30°C and that byC. lagopus better at 30°C than at 22°C. The colonization of substrate by each fungus was suppressed by the other fungus depending upon the temperature used. Hyphal parasitism and colony interactions between these fungi and also with a number of other saprophytic fungi were investigated. No antagonistic reaction was observed betweenF. udum andC. lagopus. However, these fungi were observed to be potent antagonists against other microfungi tested. The formation of fruiting bodies ofC. lagopus was also observed in the laboratory on nutrient media but more frequently on pigeon pea substrates.

The incidence of wilt disease of pigeon pea (Cajanus cajan (L.) Millsp.) caused byFusarium udum under soil treatments with various substances was studied under field conditions. The disease incidence was highly suppressed under mixed cropping withCrotalaria medicaginea. Phygon XL was found to be the most effective fungicide to reduce the incidence of the disease. The incidence of wilt disease also decreased in case of soil amended with the leaves ofC. medicaginea. Wilt incidence increased in the soil amended with the roots of pigeon pea.

Antagonism betweenFusarium udum Butler causing wilt of pigeon-pea (Cajanus cajan (L.) Millsp.) and the saprophytic microflora of the root region of the host was studied with reference to colony interaction, hyphal interference, volatile and non-volatile metabolites and staling growth products. Studies were extended to screen potential antagonists against the wilt pathogen in soil.

Background Fusaric acid (FA) has been shown to stimulate the rapid development of disease symptoms, such as necrosis and foliar desiccation. In this study, we have evaluated the phytotoxicity of FA on tomato plants (Solanum lycopersicum L.). FA induced necrotic lesions in detached leaves, which are reminiscent of hypersensitive response (HR) lesions induced by plant-pathogen interactions and other abiotic stress factors. Results FA-treated tomato leaves exhibited visible necrotic lesion as a result of cell death which was evident by Evans blue staining, enhanced reactive oxygen species (ROS) levels and DNA degradation. Changes in the generation of O2.- and H2O2 as well as the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were examined in FA-treated tomato leaves. It was observed that FA exposure stimulated oxidative burst in the leaves, resulting in a lasting activation of O2.- and H2O2 production. After first day of FA application, the H2O2 scavenging enzymes CAT and APX showed a strong activity decrease followed by gradual recovery to the control level after 2 and 3 days. Conclusion A concomitant increase in ROS production, the down regulation of antioxidative enzymes activities and upregulation of lipid peroxidation were crucial for the onset of cell death. These results suggested that FA-induced damage might result from ROS pathways. Thus, our experiments provide a useful model plant system for research on FA-induced plant cell death. Electronic supplementary material The online version of this article (doi:10.1186/s40529-014-0066-2) contains supplementary material, which is available to authorized users.