Browsing by Author "Irulappan, Vadivelmurugan"

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Combined drought and heat stress influences the root water relation and determine the dry root rot disease development under field conditions: A study using contrasting chickpea genotypes
(Frontiers Media S.A., 2022) Chilakala, Aswin Reddy; Mali, Komal Vitthalrao; Irulappan, Vadivelmurugan; Patil, Basavanagouda S.; Pandey, Prachi; Rangappa, Krishnappa; Ramegowda, Venkategowda; Kumar, M. Nagaraj; Puli, Chandra Obul Reddy; Mohan-Raju, Basavaiah; Senthil-Kumar, Muthappa
Abiotic stressors such as drought and heat predispose chickpea plants to pathogens of key importance leading to significant crop loss under field conditions. In this study, we have investigated the influence of drought and high temperature on the incidence and severity of dry root rot disease (caused by Macrophomina phaseolina) in chickpea, under extensive on- and off-season field trials and greenhouse conditions. We explored the association between drought tolerance and dry root rot resistance in two chickpea genotypes, ICC 4958 and JG 62, with contrasting resistance to dry root rot. In addition, we extensively analyzed various patho-morphological and root architecture traits altered by combined stresses under field and greenhouse conditions in these genotypes. We further observed the role of edaphic factors in dry root rot incidence under field conditions. Altogether, our results suggest a strong negative correlation between the plant water relations and dry root rot severity in chickpeas, indicating an association between drought tolerance and dry root rot resistance. Additionally, the significant role of heat stress in altering the dynamics of dry root rot and the importance of combinatorial screening of chickpea germplasm for dry root rot resistance, drought, and heat stress have been revealed.
Drought stress exacerbates fungal colonization and endodermal invasion and dampens defense responses to increase dry root rot in chickpea
(American Phytopathological Society, 2022) Irulappan, Vadivelmurugan; Kandpal, Manu; Saini, Kumud; Rai, Avanish; Ranjan, Aashish; Sinharoy, Senjuti; Senthil-Kumar, Muthappa
Drought plays a central role in increasing the incidence and severity of dry root rot (DRR) disease in chickpea. This is an economically devastating disease, compromising chickpea yields particularly severely in recent years due to erratic rainfall patterns. Macrophomina phaseolina (formerly Rhizoctonia bataticola) is the causal agent of DRR disease in the chickpea plant. The infection pattern in chickpea roots under well-watered conditions and drought stress are poorly understood at present. This study provides detailed disease symptomatology and the characteristics of DRR fungus at morphological and molecular levels. Using microscopy techniques, the infection pattern of DRR fungus in susceptible chickpea roots was investigated under well-watered and drought stress conditions. Our observations suggested that drought stress intensifies the progression of already ongoing infection by weakening the endodermal barrier and overall defense. Transcriptomic analysis suggested that the plant’s innate immune defense program is downregulated in infected roots when subjected to drought stress. Further, genes involved in hormonal regulation are differentially expressed under drought stress. These findings provide hints in terms of potential chickpea genes to target in crop improvement programs to develop climate change-resilient cultivars.
Dry root rot disease assays in chickpea: a detailed methodology
(MyJoVE Corporation, 2021) Irulappan, Vadivelmurugan; Senthil-Kumar, Muthappa
Dry root rot (DRR) disease is an emerging biotic stress threat to chickpea cultivation around the world. It is caused by a soil-borne fungal pathogen, Rhizoctonia bataticola. In the literature, comprehensive and detailed step-by-step protocols on disease assays are sparse. This article provides complete details on the steps involved in setting up a blotting paper technique for quickly screening genotypes for resistance to DRR. The blotting paper technique is easy and less expensive. Another method, based on the sick pot approach, is a mimic of natural infection and can be applied to study the interacting components—plant, pathogen, and environment—involved in the disease triangle. Moreover, in nature, DRR occurs mostly in rainfed chickpea cultivation areas, where soil moisture recedes as crop growth advances. Drought stress is known to predispose chickpea plants to DRR disease. Pathomorphological and molecular understanding of plant-pathogen interaction under drought stress can pave the way for the identification of elite DRR-resistant varieties from the chickpea germplasm pool. This article provides a stepwise methodology for the preparation of a sick pot and subsequent disease assay. Overall, the information presented herein will help researchers prepare R. bataticola fungal inoculum, maintain this pathogen, set up the blotting paper technique, prepare sick culture and sick pot, and assess pathogen infection in chickpea plants.
Dry root rot disease: Current status and future implications for chickpea production
(Springer Nature Publishing AG, 2023) Mirchandani, Rishabh; Irulappan, Vadivelmurugan; Chilakala, Aswin Reddy; Senthil-Kumar, Muthappa
Chickpea is one of the most important food legumes in the world. Several abiotic and biotic factors limit chickpea yields, notably, heat, drought, and dry root rot (DRR) disease. The occurrence and severity of DRR are further magnified by abiotic stresses. This review highlights the current impact of DRR on chickpea production in India, the deepening of the economic losses caused by DRR owing to drought, and integrated management practices to curb DRR. Management strategies and research targeting this aspect are critical because the long-term consequences of this rapidly emerging disease could be severe owing to climate change.
Dry root rot of chickpea: A disease favored by drought
(American Phytopathological Society, 2022) Rai, Avanish; Irulappan, Vadivelmurugan; Senthil-Kumar, Muthappa
Chickpea is an essential crop for protein nutrition and is grown around the world in rain-fed conditions. However, chickpea cultivation is under threat due to emerging diseases favored by drought stress. Dry root rot (DRR), an economically devastating disease, is an example. Chickpea-specific strains of a necrotic fungal phytopathogen, Macrophomina phaseolina, cause DRR. Microsclerotia of this fungus, which are capable of withstanding harsh environmental conditions, serve as primary inoculum. Initial symptoms are scattered necrotic spots in roots, progressing to rotting and withering lateral roots, accompanied by prematurely dried, straw-colored foliage. The recent rise in global temperature and worsening of drought spells have aggravated DRR outbreaks in chickpea. To date, DRR epidemiology has not been clarified in detail. Also, the literature lacks clarity on M. phaseolina taxonomy, morphology, disease progression, and diagnosis. In this article, research progress on patterns of DRR occurrence in the field and belowground and above-ground symptoms are clarified. In addition, the current understanding of taxonomy and management practices is elaborated. We also summarize knowledge of the impact of drought and high temperature on DRR severity. Further, we provide future perspectives on the importance of host resistance, QTL identification, genotype screening for the identification of resistant genotypes. The article proposes new research priorities and a corresponding plan for the mitigation of DRR.
Impact of drought stress on simultaneously occurring pathogen infection in field-grown chickpea
(Springer Nature, 2019) Sinha, Ranjita; Irulappan, Vadivelmurugan; Mohan-Raju, Basavaiah; Suganthi, Angappan; Senthil-Kumar, Muthappa
Drought stress and pathogen infection simultaneously occur in the field. In this study, the interaction of these two stresses with chickpea, their individual and combined effect and the net impact on plant growth and yield traits were systematically assessed under field and confined pot experiments. The field experiments were conducted for four consecutive years from 2014–15 to 2017–18 at different locations of India. Different irrigation regimes were maintained to impose mild to severe drought stress, and natural incidence of the pathogen was considered as pathogen stress. We observed an increased incidence of fungal diseases namely, dry root rot (DRR) caused by Rhizoctonia bataticola, black root rot (BRR) caused by Fusarium solani under severe drought stress compared to well-irrigated field condition. Similar to field experiments, pot experiments also showed severe disease symptoms of DRR and BRR in the presence of drought compared to pathogen only stress. Overall, the results from this study not only showed the importance of combined drought and DRR stress but also provided systematic data, first of its kind, for the use of researchers.
Low soil moisture predisposes field-grown chickpea plants to dry root rot disease: evidence from simulation modeling and correlation analysis
(Springer Nature Publishing AG, 2021) Sinha, Ranjita; Irulappan, Vadivelmurugan; Patil, Basavanagouda S.; Reddy, Puli Chandra Obul; Ramegowda, Venkategowda; Mohan‑Raju, Basavaiah; Rangappa, Krishnappa; Singh, Harvinder Kumar; Bhartiya, Sharad; Senthil-Kumar, Muthappa
Rhizoctonia bataticola causes dry root rot (DRR), a devastating disease in chickpea (Cicer arietinum). DRR incidence increases under water defcit stress and high temperature. However, the roles of other edaphic and environmental factors remain unclear. Here, we performed an artifcial neural network (ANN)-based prediction of DRR incidence considering DRR incidence data from previous reports and weather factors. ANN-based prediction using the backpropagation algorithm showed that the combination of total rainfall from November to January of the chickpea-growing season and average maximum temperature of the months October and November is crucial in determining DRR occurrence in chickpea felds. The prediction accuracy of DRR incidence was 84.6% with the validation dataset. Field trials at seven diferent locations in India with combination of low soil moisture and pathogen stress treatments confrmed the impact of low soil moisture on DRR incidence under diferent agroclimatic zones and helped in determining the correlation of soil factors with DRR incidence. Soil phosphorus, potassium, organic carbon, and clay content were positively correlated with DRR incidence, while soil silt content was negatively correlated. Our results establish the role of edaphic and other weather factors in chickpea DRR disease incidence. Our ANN-based model will allow the location-specifc prediction of DRR incidence, enabling efcient decision-making in chickpea cultivation to minimize yield loss.
MicroRNA397 regulates tolerance to drought and fungal infection by regulating lignin deposition in chickpea root
(John Wiley & Sons, 2023) Sharma, Nilesh Kumar; Yadav, Shalini; Gupta, Santosh Kumar; Irulappan, Vadivelmurugan; Francis, Aleena; Senthil-Kumar, Muthappa; Chattopadhyay, Debasis
Plants deposit lignin in the secondary cell wall as a common response to drought and pathogen attacks. Cell wall localised multicopper oxidase family enzymes LACCASES (LACs) catalyse the formation of monolignol radicals and facilitate lignin formation. We show an upregulation of the expression of several LAC genes and a downregulation of microRNA397 (CamiR397) in response to natural drought in chickpea roots. CamiR397 was found to target LAC4 and LAC17L out of twenty annotated LACs in chickpea. CamiR397 and its target genes are expressed in the root. Overexpression of CamiR397 reduced expression of LAC4 and LAC17L and lignin deposition in chickpea root xylem causing reduction in xylem wall thickness. Downregulation of CamiR397 activity by expressing a short tandem target mimic (STTM397) construct increased root lignin deposition in chickpea. CamiR397-overexpressing and STTM397 chickpea lines showed sensitivity and tolerance, respectively, towards natural drought. Infection with a fungal pathogen Macrophomina phaseolina, responsible for dry root rot (DRR) disease in chickpea, induced local lignin deposition and LAC gene expression. CamiR397-overexpressing and STTM397 chickpea lines showed more sensitivity and tolerance, respectively, to DRR. Our results demonstrated the regulatory role of CamiR397 in root lignification during drought and DRR in an agriculturally important crop chickpea.
Morpho-physiological traits and molecular intricacies associated with tolerance to combined drought and pathogen stress in plants
(Springer Nature, 2018) Irulappan, Vadivelmurugan; Senthil-Kumar, Muthappa
Crops in field conditions are challenged by the simultaneous occurrence of drought and pathogen stress. In the past, research was primarily focused on studying the impact of individual stresses on plants and selection of crop varieties potentially tolerant to particular stress by yield-associated morpho-physiological traits. However, several molecular responses of crop plants underlying morpho-physiological features to concurrent stresses are not similar to that of individual stresses. Certain morpho-physiological traits such as cell membrane stability, leaf water potential, stomatal movement, and root length were shown to be altered distinctly under combined stress to combat the stress condition. However, the relevance of such traits under combined stress tolerance is not precisely known. In this chapter, from the extensive literature survey, we identified several morpho-physiological changes that could be cognate with better plant performance under combined stress and represented them as traits that have potential to impart combined stress tolerance. We have comprehensively explained physiological and molecular basis for each trait and, where possible, suggested the ways to exploit the information for identification of varieties with prospective traits. Also, we proposed the need for systematically studying the underlying regulatory traits under combined stress conditions in the future.
A sick plot-based protocol for dry root rot disease assessment in field-grown chickpea plants
(John Wiley & Sons, 2021) Irulappan, Vadivelmurugan; Mali, Komal Vitthalrao; Patil, Basavanagouda S.; Manjunatha, Hanumappa; Muhammad, Saifulla; Senthil-Kumar, Muthappa
Premise: A comprehensive field-based screening protocol is lacking for dry root rot (DRR) disease in chickpea, which is caused by Macrophomina phaseolina (formerly referred to as Rhizoctonia bataticola). Here, we describe a protocol for establishing a sick plot for DRR to enable disease assessment of a large number of chickpea plants during the natural growing season. Methods and Results: We used a chickpea plot with >30% DRR incidence, and enriched the inoculum by cultivating highly susceptible chickpea plant genotypes and incorporating infected plant material into the soil. The chickpea plants were then subjected to infection in developed sick plots with various levels of soil moisture under natural field conditions. Conclusions: Our protocol provides a robust way to impose M. phaseolina infection on chickpea plants under natural field conditions and to investigate plant responses to the infection at morphological, physiological, and molecular levels. This method can also be used to screen for other soil‐borne diseases in a variety of plants.