Rice (Oryza sativa L.) is one of the most important and staple food crops in South East Asia including India plays a vital role in the food security, livelihood wellness and country’s economy (Mahajan et al., 2017). Rice is grown on an area of 43.78 mha in India with an annual production of 127.9 million tonnes approximately (Anoymous, 2022). Direct-seeded rice covers 23% of the area worldwide (Rao et al., 2007; Marasini et al., 2016; Devaraja et al., 2017). Aside from the benefits of direct-seeded rice, the productivity of direct-seeded rice is hindered by various biotic and abiotic stresses (Singh et al., 2012a,b,c, 2016, 2021). Nematode infestation is one of the major biotic factors that can cause yield losses of up to 72% in rice (Khan and Ahamad, 2020). Ditylenchus angustus, Meloidogyne graminicola, Aphelenchoides besseyi, Hirschmanniella spp. and Heterodera oryzicola are the prevalent nematode species which invade rice (Walia and Bajaj, 2003; Wesemael et al., 2011; Singh et al., 2012c). Among them, M. graminicola, an endo-parasitic sedentary nematode causing root-knot disease is the most notorious pathogen of rice. It has been reported from every rice-producing regions of the world and causes a 10.54 per cent production loss in direct-seeded rice in India, costing about 779.30 million rupees every year (Singh et al., 2007; Kumari et al., 2016; Zhou et al., 2020). When environmental conditions are favorable, the infectious juvenile stage (J₂) emerges from the egg, locates the root, and moves into the meristematic zone and feeds continuously to stimulate the production of huge galls which leads to impairment in the nutrient and water uptake and translocation (Devaraja et al., 2017; Sacchi et al., 2021). M. graminicola is an obligate biotroph causing stunting, wilting and decreased tillering; juvenile plants show chlorosis, and mature spikelets with empty florets, resulting in a substantial loss in growth and yield in rice leading to huge losses of foreign exchange (Singh et al., 2007; Jain et al., 2012; Khan and Ahamad, 2020). The direct impairment caused by root-knot nematodes can be intensified by secondary infections of the wounded plant tissues by other pathogens (Walia and Bajaj, 2003; De Waele and Elsen, 2007; Upadhyay and Dwivedi, 2008).

Conventionally root-knot nematode (RKN) is controlled by integrating chemical nematicides with cultural methods and resistant cultivars (Walia and Bajaj, 2003). Chemical nematicides are very expensive and have a negative impact on the useful microorganisms and fauna found in agricultural soil as well as could lead to the development of resistant pathogenic strains (Walia and Bajaj, 2003; Singh et al., 2007, 2012a; Upadhyay and Dwivedi, 2008). In recent decades, a number of compounds, including methyl bromide and aldicarb, have been taken off the market because of risks to the environment, human health, and non-target organisms (Kim et al., 2018; Xiang et al., 2018). Resistance development in the pathogens, residual toxicity of chemical nematicides on the environment and animal health, with the possible withdrawal of pesticides specially nematicides and soil fumigants from the schedule of pesticides and the demand for residue-free produce have obligated researchers and rice growers to explore suitable alternatives strategies for the management of RKN in agriculturally important crops including rice (Singh et al., 2007, 2012a,2012b,2012c, 2013a,2013b, 2017). Among the possible alternatives, the development of resistant cultivars with a high degree of resistance to RKN is of great importance (Walia and Bajaj, 2003; Kumari et al., 2016; Zhou et al., 2020). Moreover, availability of resistance genes in the suitable donor parents is not an easy task. As the resistance is polygenic which further increases the difficulties associated with resistance breeding programme. Further, the pyramiding/transfer of desired gene(s)/quantitative trait loci (QTLs) into commercial cultivars using a resistance breeding programme is a great challenge to rice breeders (Singh et al., 2013a; Forghani and Hajihassani, 2020; Dash et al., 2021; Sun et al., 2021). Under these circumstances, the use of microbe-based strategies is a more environment-friendly, residue-free, safer, and emerging approach to combat RKN effectively (Walia and Bajaj, 2003; Singh et al., 2012a,b,c, 2013a,2013b, 2017). In recent past, several workers evaluated and used biological control agents of microbial origin to control RKN in many crops including rice. Among them, fungal bioagents (Arthrobotrys oligospora, Monacrosporium eudermatum, Drechslerella dactyloides, Dactylaria brochopaga, Trichoderma harzianum, T. asperellum, T. virens), and bacterial (Bacillus subtilis, Paecilomyces lilacinus, B. licheniformis, B. cereus, Pseudomonas fluorescens, and Streptomyces cacaoi) are noteworthy (Singh et al., 2012a,b,c, 2013a,2013b, 2017, 2020; Abd-Elgawad and Askary, 2018; Haque et al., 2018; Zhao et al., 2018; DiLegge et al., 2019; Molinari and Leonetti, 2019; Seo et al., 2019; Singh U. B. et al., 2019; Forghani and Hajihassani, 2020; Sun et al., 2021). Similarly, few studied were made on the application of AM fungi for controlling nematodes in agriculturally important crops (van der Heijden et al., 2015; Bagyaraj et al., 2022).

Recently, several studies reported that arbuscular mycorrhizal fungi (AMF) may offer a safer alternative to pesticide use as the demand for environmental and agricultural safety grows (Harrier and Watson, 2004; Dong et al., 2006; Yang et al., 2014; Bagyaraj et al., 2022). AMF, which are found naturally in soil and behave as bio-stimulators and bio-protectors, may be extremely advantageous to sustainable agriculture by preserving plant productivity and alleviating soil-borne plant pathogens while causing no harm to the environment (Newsham et al., 1995; Smith and Smith, 2011; Koffi et al., 2013; da Silva Campos, 2020). Though there are different kinds of mycorrhiza, the most common mycorrhizal association occurring in crops important in agriculture is the arbuscular type (Babikova et al., 2013; Ceballos et al., 2013; van der Heijden et al., 2015; Bagyaraj et al., 2022). AMF are obligate root symbionts, appraised to colonize more than 80% of all land plant species and they are beneficial for the growth of host plants (van der Heijden et al., 2015). In exchange for photosynthetic carbon from their host, they boost plant growth and development by enhancing nutrient uptake (Bonfante and Genre, 2010; Smith et al., 2010; Bender et al., 2015; Bagyaraj et al., 2022) and also help plants to cope with various stresses imposed by abiotic and biotic elements, including parasitic nematodes on plants (Singh et al., 2012c; Schouteden et al., 2015; van der Heijden et al., 2015). Typically found in the rhizosphere, phytopathogenic nematodes including RKN colonize the roots of their host plants and have opposing effects on the health of those plants (Kumari et al., 2016; Zhou et al., 2020). However, few reports indicated that AMF inoculation reduces the infestation of plant roots by phytopathogenic nematodes (Agrios, 2005; Elsen et al., 2008). Growing plants with AMF inoculation in the nursery can increase their growth and safeguard them from infection caused by soil-borne phytopathogens including phytopathogenic nematodes (Elsen et al., 2008). The AMF can function as biocontrol agents through direct or indirect processes, increasing nutrient uptake and mitigating the harm caused by nematodes (Bagyaraj and Gautam Chawla, 2012). Direct impacts of AMF on the pathogen, such as competition for space or nutrients, or indirect, plant-mediated effects, can be implicated in AMF-mediated biocontrol. The latter can be further sub-divided into AMF’s influence on plant tolerance, plant defense induction, and altered plant exudation, all of which result in modifications in rhizosphere interactions (Kuila and Ghosh, 2022). The various mechanisms cannot be considered totally independent of one another, and biocontrol is most likely the outcome of a mix of mechanisms (Bell et al., 2016). Usually, AMF exhibit an antagonistic effect on plant-parasitic nematodes, and several studies have shown a significant reduction in nematodes when healthy mycorrhizal diversity present in the rhizosphere (Heinen et al., 2018; Gough et al., 2020; Poveda et al., 2020). In recent years, many investigations have been reported where AMF showed protective effects against plant parasitic nematodes (PPN) in various crop plants (Bagyaraj and Gautam Chawla, 2012; Vos et al., 2012, 2013; Alban et al., 2013; Bagyaraj, 2016; Sharma et al., 2021). However, only a few studies have been conducted so far to investigate the applications of AMF for the biocontrol of PPN in India (Bagyaraj and Gautam Chawla, 2012; Bagyaraj, 2018), and it is a need of the hour to explore these fungal symbionts for control of PPNs, especially RKN. Further there is no information available on AMF inducing key genes involved in plant defense and signaling for the biocontrol of RKN. With this in mind, the current study was conducted to investigate the role of selected AMF in the activation of plant defense responses against root-knot nematode Meloidogyne graminicola in rice (Oryza sativa L.) under direct seeded conditions.

The current day emphasis is on sustainable agriculture, which uses less of chemical inputs having adverse effect on soil health, and environment. The arbuscular mycorrhizal fungi (AMF) and other microbial inoculants play an important role in sustainable agriculture (Smith and Read, 2008; Akhmetzhanova et al., 2012; Babikova et al., 2013; Kammadavil Sahodaran et al., 2019; Lakshmipathy et al., 2019). There are several reports on AMF-soil-borne plant pathogen interactions (Bagyaraj, 2016; Singh A. et al., 2019; Singh U. B. et al., 2019). Most of the studies on AMF-root pathogens suggest that AMF decreased or mitigated the disease severity. Consistent reduction of disease symptoms has been described for fungal, bacterial and nematode pathogens. Studies conducted so far suggest that the mechanisms of suppression may be due to morphological, physiological and biological alterations in the host (Ijdo et al., 2011; Nahar et al., 2011; Khan et al., 2012; Frac et al., 2018). It includes thickening of the cell walls through lignification preventing penetration of pathogens and activation of specific defense mechanisms such as production of phytoalexins, chitinases, pathogenesis related proteins and enhanced antagonists in the mycorrhizosphere (Nahar et al., 2012; Bagyaraj, 2018). In the present investigation, inoculation of AM fungi, F. mosseae, R. fasciculatus, and R. intraradices individually and in combination under RKN challenge modulated physio-biochemical cascades in rice led to downstream signaling. Application of AM fungi not only modulates physio-biochemical pathways but also reduced the infestation, colonization, and invasion of RKN, M. graminicola. Results indicated that F. mosseae, R. fasciculatus, and R. intraradices when inoculated individually or in combination, colonized the rice roots to a greater extent (55.74 to 89.25%) thereby occupy maximum area of the root along with increased hyphal network in soil and thereby helping in enhanced plant nutrition (Brundrett, 2002, 2009; Johansson et al., 2004). Enhanced AMF colonization increased lateral root formation (secondary and tertiary rooting) and modulates the root morphology of rice which is beneficial for plant growth and development (Kyndt et al., 2012a; van der Heijden et al., 2015). During the course of screening of rice germplasm, PB-1 was found to be the most susceptible cultivar and Jasmine 85 the most resistant cultivar to M. graminicola infection at 30 DAPI. Hence, the rice-M. graminicola pathosystem with the susceptible and resistant inbred line was taken as a model system to elucidate the interactions between RKN and the host (Kyndt et al., 2012a,b; Nguyễn et al., 2014). In plants, immune system responses are in general regulated by effector-triggered immunity (ETI) and pattern-triggered immunity (PTI). PTI is generally activated when plant perceive microbial structures, in general, referred to as pathogen-associated molecular patterns (PAMPs), via the transmembrane pattern recognition receptors (PRRs) (Lee et al., 2004; Gheysen and Jones, 2006; Hewezi et al., 2010). However, ETI is activated when plants recognize specific effector molecules produced by pathogens via intracellular nucleotide-binding leucine-rich repeat (NLR) receptors, called resistance (R) proteins (Sanz-Alferez et al., 2008; Hamamouch et al., 2011;

Molinari et al., 2014) and thereby effectively up-regulate the defense mechanisms inside plant cells in response to pathogen infection and invasion (Harman et al., 2004; Singh U. B. et al., 2019; Malviya et al., 2022).

Further, mitogen-activated protein (MAP) kinase (MAPK) signaling pathways play a crucial role in plant defense, hypersensitive response (HR) reaction, immune responses, and oxidative burst to pathogen attack (Zhang and Klessig, 2001; Bari and Jones, 2009; Pieterse et al., 2009). Moreover, the microbe-mediated activation of MAPKs and downstream signaling networks in plants has not been completely defined. In general, 74 MAPKKK, 8 MAPKK, and 17 MAPK genes have been reported so far in the rice genome (Hamel et al., 2006; Reyna and Yang, 2006; Rao et al., 2010; Yang et al., 2015). They are playing a different role in signaling cascades underlying the physiological and cellular responses in rice (Tamogami et al., 1997; Schweizer et al., 1998; van Loon et al., 2006; Singh et al., 2012a). In the present investigation, RKN infection down-regulated the expression of key genes involved in the MAPK-mediated signaling pathways in the susceptible cultivar, PB-1 (−1.39 to −4.29 fold) as compared to the resistant inbred line, Jasmine 85. Further inoculation of AM fungi, F. mosseae, R. fasciculatus and R. intraradices individually or in combination up-regulated the expression of these genes in both susceptible and resistant inbred lines, PB-1, and Jasmine 85, respectively, pre-challenged with M. graminicola. This advocates a key role for MAPK signaling in rice response to RKN infection (Kumari et al., 2016; Zhou et al., 2020). To the best of our knowledge and the literatures available, this is the first report on the role of F. mosseae, R. fasciculatus, and R. intraradices in the activation of MAPK signaling in rice under pathogenic challenge of RKN M. graminicola in rice, which is further confirmed by the enhanced systemic resistance in susceptible and resistant inbred lines of rice (Pozo and Azcon-Aguilar, 2007). According to Rodriguez et al. (2009), “Plant MAPK cascades proceed through three central kinases: MAPK kinase kinase (MAPKKK); MAPK kinase (MAPKK), also known as MAPK and ERK (extracellular signal regulated kinase) kinase (MEK); and MAP kinase (MAPK or MPK).” In the present investigation, OsCERK1, OSCEBiP, OsWRKY25, OsWRKY29, OsWRKY70, OsMYB15, OsMAPKKK1, OsMAPKKK5, OsMAPK5, OsMAPK6, OsMAPK15, and OsMAPK17 were highly expressed in the rice plant primed with the selected strains of AM fungi, F. mosseae, R. fasciculatus, and R. intraradices individually or in combination. The MAPKs further activated OsWRKYs, and OsMYB transcription factors cause HR reaction and programmed cell death by modulating the generation of reactive oxygen species (ROS) at the infection site and thereby restricting the penetration, invasion and further colonization of RKN (Nahar et al., 2011; Kyndt et al., 2012a,b). Similar results were reported on the MAPK-mediated defense-priming in soybean (Glycine max) in response to Heterodera glycines infection (Bekal et al., 2003; Zhang et al., 2017; McNeece et al., 2019) and in rice against M. graminicola (Kumari et al., 2016; Zhou et al., 2020). Asai et al. (2002) clearly demonstrated the role of MAPKs signaling cascades (MEKK1, MKK4/MKK5, and MPK3/MPK6) and WRKY transcription factors (WRKY22/WRKY29) in the activation of innate immune responses in Arabidopsis thaliana. It was further reported that AtMPK3 and AtMPK6 are involved in ETI in Arabidopsis thaliana (Tsuda et al., 2009; Meng and Zhang, 2013; Choi et al., 2017; Su et al., 2018; Zhang et al., 2018) which was further endorsed by several other researchers (Pitzschke et al., 2009; Rasmussen et al., 2012; Meng and Zhang, 2013). Similarly, qRT-PCR analysis clearly indicated that RKN infection suppresses the expression of CIPKs genes (−0.75 to 4.60 fold). However, inoculation of AM fungi up-regulated the CIPKs genes in roots of susceptible and resistant inbred lines (1.20 to 9.67 fold). CIPK9 repression augmented the total RKN population in roots of susceptible inbred lines. Previous reports clearly indicated that calcium sensor (Cbl10) together with its interacting partner CIPK6 regulates plant immunity in tomato plants (De la Torre et al., 2013; Zhu et al., 2019; Huang et al., 2020). Similarly, CIPK9 regulate the downstream signaling in rice to RKN invasion (Zhou et al., 2020). Further, RKN infection significantly altered the expression level of key genes involved in the BR biosynthesis and downstream signaling in rice root. Manifolds suppression was reported in the expression of the gene involved in the BR signaling in susceptible inbred line PB-1 as compared to the resistant line, Jasmine 85. However, AM inoculation up-regulated the BR biosynthesis genes in both susceptible and resistant inbred lines at 30 DAPI signifying the presence of diverse BR functions responding to RKN infection and disease development (Song et al., 2018). Our findings clearly signify a negative correlation between the activation of BR biosynthesis genes and RKN population on rice roots. These findings are also in agreement with the observation of earlier researchers (Kumari et al., 2016; Song et al., 2018; Zhou et al., 2020). In the present investigation, it was observed that plants inoculated with AM fungi showed significantly higher accumulation of antioxidants and defense-related mediator molecules/enzymes in them leading to increased cell wall lignification and reduction in the RKN invasion. qRT-PCR results also showed that RKN invasion negatively regulates the jasmonates biosynthesis genes, OsAOS2, OsJMT1, and OsJAMYB. However, these genes were highly up-regulated in the AM-inoculated plant which clearly indicated that AM inoculation has a positive impact on JA-mediated defense priming in rice (Seo et al., 2001; Kyndt et al., 2012a,b; Liu et al., 2013; Li et al., 2015; Zhou et al., 2020). Similar to BR biosynthesis and signaling, jasmonate biosynthesis and accumulation of jasmonic acids significantly affect the phenolics content in many crops (Wang and Zheng, 2005; Heredia and Cisneros-Zevallos, 2009). In the present study, the key genes involved in the ET biosynthesis (OsACS1, OsACO7, OsEIN2, and OsERF1) were suppressed upon RKN invasion in rice, while AM inoculation up-regulated these genes in resistant and susceptible inbred lines. ET biosynthesis and ET-mediated downstream signaling positively regulate the defense cascades in crop plants under biotic and abiotic stresses (Leon-Reyes et al., 2009; Molinari et al., 2014; Yuan et al., 2018; Zhou et al., 2020). Along with defense cascades, ET biosynthesis play a crucial role in IAA-mediated lateral root development, tissue differentiation, photosynthesis and overall plant growth and development. Earlier reports also emphasized that ET signaling is known to regulate plant response to RKN invasion (Yuan et al., 2018; Zhou et al., 2020).

Despite being stress-inducible, systemic mRNA levels of pathogenesis-related proteins, OsPR-1, OsPR-2, OsPR-5, and OsPR-10 did not significantly change in the roots inoculated with AM fungi individually and pre-challenged with M. graminicola (Xiong and Yang, 2003; Leon-Reyes et al., 2009; Goto et al., 2013; Goverse and Smant, 2014). In contrast, significantly higher up-regulation was observed in the roots inoculated with consortia of AMF. The systemic mRNA levels of OsPR-1, OsPR-2, OsPR-5, and OsPR-10 were consistently suppressed in the roots of PB-1 under RKN invasion at 30 DAPI (Figure 7). Among all defense mechanisms, PR proteins are the indispensable component of innate immune responses in plants under biotic or abiotic stress conditions (Sarma et al., 2015; Lv et al., 2016; Yuan et al., 2018; Zhou et al., 2020). The biosynthesis and accumulation of PR proteins protect the plants from further infection by not only accumulating locally in the infected and surrounding tissues but also in remote uninfected tissues. PR proteins are also involved in the synthesis of phytoalexins, regulation of oxidative burst, HR response or SA-mediated systemic acquired resistance against pathogenic infection including phytopathogenic nematodes (Harman et al., 2004; Sanz-Alferez et al., 2008; Pieterse et al., 2009; Vlot et al., 2009; Singh et al., 2020). Further structure, biochemistry, source, regulation of gene expression and nature of stress, define their role in defense mechanism of various PR proteins (Sanz-Alferez et al., 2008; Bari and Jones, 2009; Hamamouch et al., 2011; Kumari et al., 2016). Phenylpropanoid pathway is the first line of plant defense imparting host resistance by reprogramming the downstream signaling involving activation and accumulation of antioxidant enzymes (PAL, TAL, Pox, APx, etc.) and various defense-related biomolecules such as phytoalexins, callose, pectin, lignin derivatives and other metabolites toxic to the pathogens (Wuyts et al., 2006, 2007; Singh U. B. et al., 2019; Singh et al., 2020). Cell wall lignifications and deposition of pectin substances between the cells give mechanical strength to the plant tissues (Singh et al., 2020). In the present study, results clearly showed that RKN invasion repressed the expression of key genes of phenylpropanoid cascades and took benefit of that during the penetration and invasion of the root tissues. At the same time, plants bioprimed with AM fungi alone or in combination upregulated the expression profile of key genes of phenylpropanoid pathways and increased the activities of PAL, TAL, Pox, APx, etc. While in the resistant inbred line, the fold expression was significantly higher as compared to the susceptible cultivar. Similar effects were also observed in terms of the expression profile of key genes involved in lignin and callose biosynthesis (Wuyts et al., 2006, 2007; Hao et al., 2008; Portillo et al., 2013). Increased lignifications and callose deposition in response to RKN invasion provide additional adoptive mechanisms and strength to resistant inbred lines. Due to the antimicrobial and non-degradable nature of lignin, pectin and callose restrict the entry of pathogens including phytopathogenic nematodes and protect plants even under conducive conditions (Dixon and Paiva, 1995; Wuyts et al., 2006, 2007; Hao et al., 2008; Portillo et al., 2013; Singh U. B. et al., 2019; Singh et al., 2020).

Apart from this, AMF have increased the accumulation of total chlorophyll, total soluble sugar and total protein in rice plants even under pathogenic stress. It is a well-established fact that AMF have the ability to mobilize diffusion-limited nutrients and water from distant places and supple to plants those helping plant growth and productivity (Opik et al., 2006; Parniske, 2008; Bagyaraj et al., 2022). Increased uptake and translocation of mineral nutrients contribute to improved total chlorophyll, total soluble sugar and total protein content in the plants which lead to better plant growth and vigor (Plett et al., 2014). It has also been reported that RKN invasion led to the overproduction of reactive oxygen species (ROS) at the cellular level (Singh U. B. et al., 2019; Singh et al., 2020). In the present investigation, manifold increases in the activities of antioxidant and defense-related enzymes were recorded in plants primed with consortia of three AMF F. mosseae, R. fasciculatus and R. intraradices compared to plants primed individually with each of them and conferring resistance to RKN invasion. Among them, ascorbate peroxidase, peroxidase, catalase, and superoxide dismutase are the most important. These antioxidant enzymes are known to reduce ROS more efficiently. These results are in agreement with the findings of other earlier researchers (Lorito et al., 2010; Singh et al., 2011). Unlike AM fungi, roots primed with plant growth-promoting microorganisms modulated different cascades related to defense related metabolome in plant systems over a time period and activated plant growth and defense biome directly and/or indirectly (Ahn et al., 2007; Bakker et al., 2013; Facelli et al., 2014; Alori et al., 2017; Singh A. et al., 2019; Singh U. B. et al., 2019). As revealed by infection bioassay in the present study (Table 1), a significantly higher number of galls/root system, egg mass/root system and J₂s/root system was reported in the roots of susceptible inbred line, PB-1 compared to the resistant inbred line, Jasmine 85 during early stage of infection (30 DAPI). A similar trend was also recorded at 45 DAPI. It is well established that the resistant inbred line, Jasmine 85 contains several resistant genes/QTLs as compared to susceptible ones which protect plants from severe invasion and development of root gall (Ryan and Graham, 2002; Selosse and Rousset, 2011). Further, inoculation of AM fungi individually or in combination primed the plant and activated several genes involved in the plant defense which gives addition support to the plant defense even under RKN invasion. Increased lignifications and callose deposition restrict the entry of J₂s and the invasion caused by them. AM inoculation not only reduced the RKN invasion but also increased plant growth attributes under the pathogenic stress of M. graminicola. In short, the present study describes well-coordinated mode of action of AM fungi during RKN invasion, expression of defense-related genes regulating several pathways, accumulation and activities of mediator molecules/enzymes, callose deposition and cell wall lignification ultimately leading to the reduction in RKN invasion, disease development and improved plant growth under biotic stress condition (Figure 12).

Root priming with AMF, F. mosseae, R. fasciculatus and R. intraradices individually or in combination significantly increased the transcript accumulation of key genes involved in the signaling and plant defense in the susceptible and resistant inbred lines, PB-1 and Jasmine 85 pre-challenged with RKN, M. graminicola. The present study, has summarized the detailed investigation of AM fungi-induced activation and accumulation of defense-related biomolecules in rice plants even under pathogenic stress conditions. These AMF could be very promising microbial inoculants for the activation of defense pathways in a cooperative manner under pathogenic stress. Inoculation of AMF also increased lignin content in roots which further reduces the pathogen infection, colonization and invasion. Results clearly indicated that inoculation of AM fungi alone or in combination significantly reduced the number of gall/root system, egg mass/root system and J₂s/root system at 30 and 45 DAPI. Inoculation of AM fungi to rice led to modifications in the root architecture that supports efficient uptake of nutrients and water and promotes plant growth even under pathogenic stressed conditions. With the help of these findings, we concluded that AMF inoculation could be a potential alternative to toxic chemical nematicides and could be applied at a larger scale to manage root-knot disease in rice at experimental plots and commercial production after extensive field evaluation at farmers’ fields.

The original contributions presented in this study are included in the article/Supplementary material, further inquiries can be directed to the corresponding authors.

DM, PS, US, JR, and HS conceived and designed the experiments. DB supplied the AM fungi. PS, RV, and AK given the resistant and susceptible inbred lines/cultivars of rice. DM, PS, and US performed the experiments. PS, PKB, US, and RAF analyzed the data. DM, SP, PK, PS, and US wrote the manuscript. AK, DB, JR, MA, and SD edited and given final touch to the manuscript. All authors reviewed the manuscript and given approval to the final version.