Browsing by Author "Amrita Saxena"

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Advances in Trichoderma biology for biocontrol applications
(Elsevier, 2025) Amrita Saxena; Riddha Dey; Surya Prakash Dube; Richa Raghuwanshi
Lauded globally as a potent biopesticide and biofertilizer, Trichoderma can be the mainspring for the much needed “Greener Revolution” in the world required to restore food security for the ever-teeming global population. The uniqueness of Trichoderma that singles it out from other microbes is its several survival strategies. It owns a high capability of “rhizosphere competence,” a term aptly suggested for microbial growth along with plant roots. The fungus efficiently colonizes the plant roots, establishing along with the existing microbial communities. Reshaping the soil microbiome has also been a major mechanism of plant growth promotion by Trichoderma. Its evolving lifestyle has not only made it successful in establishing a beneficial cross-talk with the host plant toward providing tolerance against abiotic and biotic stresses but also in activating transcriptional memory in plants for future stress responses. The chief criteria that it selects for survival is antagonism or biocontrol. The competition for nutrients and space primarily steers such a kind of activity. Trichoderma secretes diverse volatile compounds including alcohols, aldehydes, ketones, ethylene, hydrogen cyanide, and monoterpenes, as well as non-volatile compounds including peptaibols and diketopiperazine-like gliotoxin and gliovirin which are known to exhibit antibiotic activity. Another important mechanism adopted by Trichoderma is mycoparasitism (penetration/infection) and the production of cell wall-degrading enzymes for successful inhibition of phytopathogenic fungi. The role of Trichoderma in sustainable agriculture is expanding with the unrevealing secondary metabolites, and it is commercialized. The generation of new bioformulations based on microbial metabolites and living consortia can be the future solutions for the increasing toxins in soil and underground water. © 2025 Elsevier Inc. All rights reserved.
Chilli anthracnose: The epidemiology and management
(Frontiers Media S.A., 2016) Amrita Saxena; Richa Raghuwanshi; Vijai Kumar Gupta; Harikesh B. Singh
Indian cuisine is renowned and celebrated throughout the world for its spicy treat to the tongue. The flavor and aroma of the food generated due to the use of spices creates an indelible experience. Among the commonly utilized spices to stimulate the taste buds in Indian food, whole or powdered chilli constitutes an inevitable position. Besides being a vital ingredient of of Indian food, chilli occupy an important position as an economic commodity, a major share in Indian economy. Chilli also has uncountable benefits to human health. Fresh green chilli fruits contain more Vitamin C than found in citrus fruits, while red chilli fruits have more Vitamin A content than as found in carrots. The active component of the spice, Capsaicin possesses the antioxidant, anti-mutagenic, anti-carcinogenic and immunosuppressive activities having ability to inhibit bacterial growth and platelet aggregation. Though introduced by the Portuguese in the Seventeenth century, India has been one of the major producers and exporters of this crop. During 2010-2011, India was the leading exporter and producer of chilli in the world, but recently due to a decline in chilli production, it stands at third position in terms of its production. The decline in chilli production has been attributed to the diseases linked with crop like anthracnose or fruit rot causing the major share of crop loss. The disease causes severe damage to both mature fruits in the field as well as during their storage under favorable conditions, which amplifies the loss in yield and overall production of the crop. This review gives an account of the loss in production and yield procured in chili cultivation due to anthracnose disease in Indian sub-continent, with emphasis given to the sustainable management strategies against the conventionally recommended control for the disease. Also, the review highlights the various pathogenic species of Colletotrichum spp, the causal agent of the disease, associated with the host crop in the country. The information in the review will prove of immense importance for the groups targeting the problem, for giving a collective information on various aspects of the epidemiology and management of the disease. © 2016 Saxena, Raghuwanshi, Gupta and Singh.
Deciphering the Pathogenic Behaviour of Phyto-Pathogens Using Molecular Tools
(Wiley Blackwell, 2014) H.B. Singh; Akansha Jain; Amrita Saxena; Akanksha Singh; Chetan Keswani; Birinchi Kumar Sarma; Sandhya Mishra
The early detection and identification of plant pathogens are an integral part of successful disease management. Rapid identification of a plant pathogen provides appropriate control measures that could be applied prior to further spread of the disease or its introduction. The classical approach to plant disease diagnosis at the preliminary stage involved identification by visual symptoms followed by laboratory identification using selective media and microscopy to identify the infecting pathogens. But the conventional methods are a relatively slow process and often require skilled taxonomists for reliable identification of the pathogens. Therefore, in the past decade, major focus has shifted to the development of rapid, accurate and low cost methods with application in plant pathogen diagnosis. These methods include enzyme-linked immunosorbant assay (ELISA), the use of monoclonal antibodies, and DNA and PCR-based technologies which increase the sensitivity of pathogen detection. Rapid diagnosis and on-site quantification of phytopathogens and mapping them at locations of high disease incidence would enable the timely forecast of the advent of disease and would enable the farmers, agricultural authorities and research institutions to perform various management practices to control the disease. The present chapter deals with recent advances in molecular methods developed to detect and identify the four major classes of plant pathogens:viz. bacteria, fungi, nematodes and virus. © 2014 by John Wiley & Sons, Ltd. All rights reserved.
Differential Reprogramming of Defense Network in Capsicum annum L. Plants Against Colletotrichum truncatum Infection by Phyllospheric and Rhizospheric Trichoderma Strains
(Springer, 2020) Amrita Saxena; Sandhya Mishra; Shatrupa Ray; Richa Raghuwanshi; Harikesh Bahadur Singh
Induction of defense response in host plants by the Trichoderma spp. has been attributed as one of the major mechanisms leading to inhibition of the pathogenic ingression. The present study sheds light on the mechanisms employed by the Trichoderma isolates, obtained from phyllosphere (BHUF4) and rhizosphere (T16A), to modulate the defense network of chili plant under Colletotrichum truncatum challenge. Plants treated with both the Trichoderma strains exhibited significant accumulation of phenols under C. truncatum challenge with maximum increment recorded for capsaicin (16.1-fold), ferulic acid (5.03-fold), quercetin (5.36-fold), salicylic acid (94.88-fold), and kaempeferol (6.22-fold). Phenol accumulation corresponded to the subsequent defense gene expression pattern. When compared to the pathogen-challenged control plants, enhanced expression of PR1, PIK1, CHI, GLU, Cdef, and SAR genes was recorded in the Trichoderma-treated plants acting as a biocontrol agent (BCA). The results of the present study suggest that to strengthen the defense pathways in the host plant, the mechanisms employed by Trichoderma isolates differ and depend upon their origin and site of application. While phyllospheric Trichoderma isolate (BHUF4) employed the systemic acquired resistance (SAR) pathway, the rhizospheric Trichoderma strain (T16A) used the induced systemic response (ISR) pathway for eliciting the defense response in the host plant under C. truncatum challenge. The study signifies how Trichoderma strains obtained from different origin and when applied at different sites in plant judiciously reprogram the defense network of the host plant to provide robust protection against phytopathogens. In the present case, overall protection is provided to the chili plants against the foliar or underground attack of C. truncatum. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Effect of Azoxystrobin Based Fungicides in Management of Chilli and Tomato Diseases
(Springer India, 2016) Amrita Saxena; Birinchi Kumar Sarma; Harikesh Bahadur Singh
Chilli and tomato are two major vegetable crops of the world with India being one of the important producers. Vulnerable to many diseases, chemical control has been the most effective method adopted by farmers to protect their crops from fungal pathogens. The pathogens have started developing resistance against the conventionally used fungicides recommended to the farmers. Second generation fungicides have proved as a new ray of hope in better management of diseases under field conditions. Strobilurins have not been much tested in Indian subcontinent for their efficacy against many diseases. Two azoxystrobin based fungicides ONESTAR 23 % SC and AMISTAR 23 % SC were used to study their efficacy along with other commonly used fungicides, against blight disease of tomato and fruit rot and powdery mildew of chilli in Varanasi for 2 years from 2010–2011 to 2011–2012. Maximum disease reduction was observed in plants treated with Onestar 23 % SC and Amistar 23 % SC in both chilli and tomato (70–78 % reduction recorded in case of chilli while 69–71 % recorded in case of tomato) with enhanced yield (1.29 fold increment in chilli and 1.39 fold increment in tomato) in both seasons. No phytotoxicity symptoms were observed in the plants against the fungicides tested suggesting the importance of using fungicides in proper dose and at proper interval. © 2014, The National Academy of Sciences, India.
Elevation of Defense Network in Chilli Against Colletotrichum capsici by Phyllospheric Trichoderma Strain
(Springer New York LLC, 2016) Amrita Saxena; Richa Raghuwanshi; Harikesh Bahadur Singh
Biocontrol strategies have been mainly focused on proposing the use of biocontrol agents (BCAs) isolated from the rhizospheric region of the plant for protection against phytopathogens. The present study evaluates the effectiveness of phyllospheric Trichoderma isolates in elevating the defense responses in chilli against Colletotrichumcapsici infection and comparing its efficiency to the conventionally recommended rhizospheric Trichoderma strains. The elicitation of the defense network in the plants was analyzed using biochemical assays for important enzymes, that is, PAL, PO, PPO, TPC, SOD along with the total protein level in challenged plants over untreated and unchallenged control plants. The results recorded 2.1, 5.18, 3, 0.67, and 0.5-fold increases in TPC, PAL, PO, PPO, and total protein content in BHUF4 (phyllopsheric Trichoderma isolate)-treated plants when compared to control plants under C. capsici challenge. This was at par with the increment recorded in T16A (rhizospheric Trichoderma isolate)-treated chilli plants. The increment in growth parameters was also recorded after treatment with the isolated Trichoderma strains. Interestingly, the phyllospheric isolate (BHUF4) treatment recorded comparable growth promotion in chilli plants recording 36, 62, and 60 % increases in one of the major parameters of plant growth, that is, root length, no. of leaves, and dry weight, respectively. This study proposes the use of combined application of both rhizospheric as well as phyllospheric Trichoderma isolates for better and all around protection of plants against foliar as well as soil phytopathogens. This would be a novel approach in biological control strategy for better management of anthracnose disease of chilli. © 2015, Springer Science+Business Media New York.
Harnessing plant-microbe interactions for enhanced protection against phytopathogens
(Springer India, 2015) Sandhya Mishra; Akanksha Singh; Chetan Keswani; Amrita Saxena; B.K. Sarma; H.B. Singh
Beneficial plant-microbe interactions have utmost importance for enhancing plant growth, improving soil structure, and managing plant diseases. Not surprisingly, such mutual interactions, where plants provide nourishment to rhizospheric microbes and in return microbes help in facilitating plant growth and stress amelioration, actually lay the foundation of sustainable agriculture. To cope with the major challenge of pathogen attack, beneficial rhizospheric microbes have proven their efficacy by induced systemic resistance (ISR). Therefore, such microbes are increasingly used in the form of biofertilizers and biopesticides. Moreover, such plantmicrobe interactions elicit a range of defense- responsive activities in order to combat the pathogen challenge. The main microbes- mediated defense strategies adopted by plants include activation of antioxidant status of the plant by reprogramming defense-related enzymes, modulation of quorum sensing phenomenon, and activation of phenylpropanoid pathway leading to phenolics production, lignin deposition, and transgenerational defense response. In this chapter, we highlight the relevance of beneficial interactions between plant and microbes in enhancing plants’ innate immune system against pathogen attack. This review provides a better understanding of the recent advances and major outcome of positive plant-microbe interactions and linking their relevance to plant defense response. © 2015 Springer India. All rights reserved.
Trichoderma species mediated differential tolerance against biotic stress of phytopathogens in Cicer arietinum L
(2015) Amrita Saxena; Richa Raghuwanshi; Harikesh B.ahadur Singh
Trichoderma spp. have been reported to aid in imparting biotic as well as abiotic tolerance to plants. However, there are only few reports unfolding the differential ability of separate species of Trichoderma genera generally exploited for their biocontrol potential in this framework. A study was undertaken to evaluate the biocontrol potential of different Trichoderma species namely T. harzianum, T. asperellum, T. koningiopsis, T. longibrachiatum, and T. aureoviride as identified in the group of indigenous isolates from the agricultural soils of Eastern Uttar Pradesh, India. Their biocontrol potential against three major soilborne phytopathogens, i.e., Sclerotium rolfsii, Sclerotinia sclerotiorum, and Colletotrichum capsici was confirmed by dual culture plate technique. Efficient mycoparasitic ability was further assessed in all the isolates in relation to chitinase, β-1,3 glucanase, pectinase, lipase, amylase, and cellulase production while equally consistent results were obtained for their probable phosphate solubilization and indole acetic acid (IAA) production abilities. The selected isolates were further subjected to test their ability to promote plant growth, to reduce disease incidence and to tolerate biotic stress in terms of lignification pattern against S. rolfsii in chickpea plants. Among the identified Trichoderma species, excellent results were observed for T. harzianum and T. koningiopsis indicating better biocontrol potential of these species in the group and thus exhibiting perspective for their commercial exploitation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Unrealized Potential of Seed Biopriming for Versatile Agriculture
(Springer India, 2015) H.B. Singh; Kartikay Bisen; Chetan Keswani; Sandhya Mishra; Amrita Saxena; Amitava Rakshit
Seeds are the crucial input in agriculture as most of the world food crops are grown from seeds and they are circulated at large scale in international trade. However, many plant pathogens can be seed transmitted, and seed distribution is an extremely capable way of introducing plant pathogens into fresh areas as well as a means of endurance of the pathogen between growing seasons. In past decades, chemicals are widely used for seed treatment as a potent approach towards disease control; however, rising concern about their negative impact on the environment and human health minimizes their use and promotes biological control for plant pathogens. Biopriming is a currently popular approach of seed treatment which includes inoculation of seed with beneficial microorganisms (biological aspect) and seed hydration (physiological aspect) to protect the seed from various seed- and soilborne diseases. Biopriming treatment is able to incite changes in plant characteristics and facilitate uniform seed germination and growth associated with microorganism inoculation. Seed priming and osmo-priming are commonly being used in many horticultural crops to amplify the growth and uniformity of germination. However, it may be used alone or in combination with biocontrol agents to advance the rate of seed emergence and minimize soilborne diseases. On the other hand, some biocontrol agents are used as seed dressers and are able to colonize the rhizosphere, helping seeds to resist various abiotic stresses such as salinity, drought, low fertility and heavy metal stress, etc. Therefore, biopriming is becoming a viable alternative for inorganic chemicals. © Springer India 2015.