First Report of rattail cactus necrosis-associated virus Infecting Prickly pear (Opuntia macrocentra) in the United States.

Black-spined prickly pear (Opuntia macrocentra Engelmann; Cactaceae) is a cactus native to Arizona, New Mexico, Texas, and northwest Mexico. The plant is often grown for ornamental purposes in the United States. In February 2023, virus-like symptoms such as concentric ringspots and chlorotic spots were observed on O. macrocentra plants grown at the vicinity of Maricopa County Cooperative extension, University of Arizona, Phoenix, AZ (33°24'24.6"N, 111°59'15.3"W). Total RNA was extracted from two samples (YPHC-60-A and YPHC-60-B), following the protocol by Tzanetakis et al. (2007). Reverse transcription polymerase chain reaction (RT-PCR) was performed with degenerate tobamovirus, TobamodF/TobamodR (Li et al. 2018) and potexvirus, 1RC, Potex 2RC, and Potex 5 (van der Vlugt and Berendsen 2002) primers. An expected amplicon of ~880 bp was obtained from both samples using TobamodF/TobamodR primers, while no amplification was observed with potexvirus primers. Further, RT-PCR was carried out using species-specific primers to detect cacti related tobamoviruses: cactus mild mottle virus (CMMoV), rattail cactus necrosis-associated virus (RCNaV) (Park et al. 2018) and Opuntia virus 2 (Salgado-Ortiz et al. 2020). Amplicons of ~540 bp were amplified from both samples using RCNaV specific primers, whereas no amplification was obtained using CMMoV and Opuntia virus 2 specific primers. Then, the amplicons from both YPHC-60 (A-B) isolates (~540 bp) were Sanger sequenced and shared 99.22% nucleotide identity to each other. A BLAST search revealed 93% nucleotide identity with RCNaV CP sequences (KY581586.1, JF729471, and MT130378.1). The sequences were submitted in the GenBank (accessions no. OQ914798 and OR828526). Furthermore, complete RCNaV- RNA dependent RNA polymerase (RdRP) gene was amplified using primers 3490-s-5'GTAGGTGGTACCGCATAGCA-3'; 3490as 5'AAACGCAAGTCMRYGACYGA-3' (designed in this study from accession no. JF729471.1, position 3490-3509 and 4905-4925). The expected amplicons of ~1,500 bp were obtained from both YPHC-60 (A-B) samples and sequenced (GenBank: OQ914799 and OR823954) showing 87.5 % identity with RCNaV sequences (JF729471.1 and NC_016442.1). The maximum-likelihood phylogenetic tree clustered YPHC-60 (A-B) isolates in a single clade with other RCNaV isolates. RCNaV virus particles were isolated from YPHC-60 (A-B) and submitted for RNA extraction, testing positive for RCNaV by RT-PCR. Sap extract of YPHC-60 (A-B) prepared in 0.01 M phosphate buffer (pH =7.0) was used to mechanically inoculate 3 indicator plant species (n=10): Phaseolus vulgaris, Medicago sativa, and Cucumis melo. Also, infected tissue was used to graft Opuntia sp. plants. Symptoms such as local lesions were observed on M. sativa and vein thickening on P. vulgaris 14 days post-inoculation, while Opuntia sp. showed chlorosis 30 days after grafting. RCNaV infection in mechanically inoculated P. vulgaris, M. sativa, and Opuntia sp. was also confirmed through RT-PCR. C. melo and non-inoculated control plants did not show any symptoms, nor tested positive through RT-PCR. RCNaV has been reported earlier to infect cactus species in South Korea (Park et al. 2018) and O. albicarpa in Mexico (De La Torre-Almaráz et al. 2016), where it was found in several orchards. To the best of our knowledge, this is the first report of RCNaV infecting O. macrocentra in the United States. This study highlights that RCNaV is easily transmitted mechanically or by grafting, which could impact the nursery industry as most cacti are clonally propagated.

First Report of Pitaya Virus X Infecting Lophocereus schottii f. mieckleyanus (Thin-Stemmed Totem Pole Cactus) in the United States.

Lophocereus is a genus of three species of columnar cacti native to Arizona and Mexico (Lodi, 2015). These cacti produce several tall, ascending, columnar stems that branch at the base in a candelabra-like arrangement. The most common species, L. schottii is known as the senita cactus. Several unusual knobby-stemmed spineless forms of senita cactus have been found in nature in Baja California, Mexico, which are collectively known as totem pole cacti. The thin-stemmed totem pole cactus, L. schottii f. mieckleyanus is an important part of landscapes in southern Arizona. Cacti are clonally propagated which makes viral infections of economic importance in the ornamental/nursery industry. In February 2023, virus-like symptoms, such as mosaic and chlorotic spots were observed on the stems of L. schottii f. mieckleyanus grown in a nursery in Phoenix, AZ, USA. Total RNA was extracted from two symptomatic cacti (YPHC-61 A & B) following the protocol by Tzanetakis et al. (2007), and cDNA was synthesized using the Superscript IV Reverse Transcriptase (Invitrogen, Vilnius, Lithuania). Reverse transcription polymerase chain reaction (RT-PCR) performed with cactus virus X specific primers (Kim et al. 2016) targeting the coat protein (CP) gene failed to generate any amplicon, while potexvirus-replicase primers, Potex 2RC and Potex 5 (van der Vlugt and Berendsen 2002) targeting RNA-dependent RNA polymerase (RdRp) gene amplified an expected amplicon of ~580 bp from both the samples. One of the amplicons was Sanger sequenced and showed 90.7% nucleotide (nt) identity with pitaya virus X (PiVX) in the GenBank (MN982522). Sequence was submitted in the GenBank under the accession number OR425049. PiVX is a new species of the genus Potexvirus and is named after its origin from pitaya (Hylocereus spp.). Further, RT-PCR was conducted with PiVX-specific primers, CP 110F/CP 604R targeting CP gene (Bae and Park 2022) and RdRp gene (RdRp F 5' GCGTGGGCCCTGGAAAA-3'/RdRp R 5' CTAAGATTCATCAATTCACCTCTCC-3') (this study). Amplicons of ~500 and 1100 bp were obtained using primers, CP 110F/CP 604R and RdRp F/RdRp R, respectively. A BLAST search revealed 90.5% nt identity to PiVX CP sequences (OM802135 and OM802134) and 87.3% nt identity to RdRp sequences (MN982523 and LC654699) in the GenBank. Sequences of isolates YPHC-61A and YPHC-61B were submitted in the GenBank under accession numbers, OQ915350 and PP182358 (CP gene) and OQ915351 and PP209539 (RdRp gene). Phylogenetic analysis based on the combined sequence datasets of CP and RdRp genes also grouped YPHC-61A and YPHC-61B with PiVX isolates and separated from other potexviruses species. For a bioassay of the virus, sap extract from symptomatic cactus was mechanically inoculated onto indicator plant species, i.e., beans, alfalfa, and melon. Ten days post- inoculation, chlorotic lesions were observed on beans and alfalfa plants, while melon and mock-inoculated plants did not show any symptoms. Similarly, L. schottii f. mieckleyanus plants grafted with infected cactus showed chlorotic spots after 30 days post grafting. Mechanically inoculated beans, alfalfa, and cactus plants were found to be positive for PiVX based on RT-PCR and Sanger sequencing. PiVX has earlier been detected on Notocactus leninghausii f. cristatus (Park et al. 2018) and dragon fruit (Selenicereus undatus) plants in South Korea (Bae and Park 2022). To our knowledge, this is the first report of PiVX on L. schottii f. mieckleyanus in the United States and worldwide.

First Report of Rhizopus arrhizus (syn. R. oryzae) causing Sunflower Head Rot in Arizona, USA.

Sunflower (Helianthus annuus) is an ornamental, edible-seed, and important oil source plant in the USA. In June 2023, head rot was observed in sunflowers grown in an experimental field at Yuma County Cooperative Extension, University of Arizona, AZ (32°42'35.5"N, 114°42'25.0"W). The disease incidence was of >70%. Head lesions were dark-brown and extended through the head to the bracts and stem. White to gray mycelia and black sporangia-like structures were also observed on sunflower heads. Symptomatic plants (n =10) were sampled to determine the disease causing agent. Five symptomatic tissues for each plant (0.5 to 1 cm) were submitted to surface sterilization by dipping in 75% ethanol 2min, 1% NaOCl for 2 mins and rinsing with sterile water. Once sterilized, the tissues were plated on potato dextrose agar (PDA) plates and incubated at 25±0.2 °C. After two days, hyaline mycelia were observed on PDA which turned white after 7 days. A total of 50 isolates were obtained, of which ten were randomly selected and purified by the hyphal-tip method and later used for morphological analysis. Microscopic observations revealed hyaline and aseptate hyphae, sporangiophores measuring 900 to 1.2000 µm in length and dark-brown sporangium (72 to 144 µm, mean = 90). The columella was sub-globose, and the sporangiospores ranged from 7.29 to 9.37 µm in size (mean = 7.5 µm). The morphological characteristics described above were similar for the ten isolates and were in accordance with the species R. arrhizus as described by (Gryganskyi et al. 2018). Genomic DNA was extracted from three randomly chosen isolates using The DNeasy Plant kit (Qiagen) and used for further molecular identification. The internal transcribed spacer (ITS) region was amplified using ITS1/ITS4 primers (White et al. 1990) and then Sanger sequenced. The sequences shared 100% nucleotide identity with each other (GenBank accession numbers PP747852, PP747853 and PP747854) and shared 100% identity to R. arrhizus GenBank accessions (MT316366.1, MN547407.1). One isolate, YPHC-94-A, was randomly selected for Phylogenetics and Pathogenicity analyses. Phylogenetics analysis based on sequence data of ITS showed that the isolated YPHC-94-A clustered together with R. arrhizus species (Zhang. 2023). Pathogenicity test was conducted by inoculating four sunflower varieties (American giant, Lemon queen, Solar eclipse and Mammoth) (n = 12 for each variety). Plant heads were inoculated with a disc of mycelia (0.5 cm2) and incubated for 24 h at 30 ±2 °C and 94% RH. Five uninoculated plants of each variety were used as controls. Head rot symptoms were observed within 3-5 days on inoculated plant post inoculation depending on the variety, whereas the control plants stayed asymptomatic. R. arrhizus was re-isolated from all the inoculated plants and was morphologically and molecularly identical to the field isolates, thus fulfilling Koch's postulates. R. arrhizus has already been reported in different US regions (Sanogo et al. 2010), however, to the best of our knowledge this is the first report in Arizona. Due the high disease incidence and pathogen aggressiveness found in the environmental conditions of the U.S southwest desert, we consider sunflower Head rot a potential risk for sunflower production in Arizona as well as the large population of wild sunflowers in the State.

First Report of Charcoal Rot Caused by Macrophomina phaseolina on Stevia rebaudiana in Arizona, USA.

Stevia (Stevia rebaudiana Bertoni) is an important medicinal crop grown worldwide. Leaves of stevia contain a non-caloric sweetener, stevioside, which is used as a substitute to artificial sweeteners. In August 2022, symptoms of chlorosis, wilting, and root rot were observed in about 30 % of stevia plants growing at the Agricultural Station at Yuma Agricultural Center, Yuma, AZ, USA (32.7125° N, 114.7067° W). Infected plants initially showed chlorosis and wilting, and the plants eventually died with foliage remaining intact to the plant. Cross sections of the crown tissue of affected stevia plants showed necrotic tissue and a dark brown discoloration in areas of the vascular and cortical tissues. Dark brown microsclerotia were observed on stem bases and necrotic roots of the infected plants. Five symptomatic plants were sampled to isolate the pathogen. Root and crown tissues (0.5 to 1 cm) were surface disinfested with 1% sodium hypochlorite for 2 min, rinsed three times with sterile water, and plated onto potato dextrose agar (PDA). All the five isolates displayed rapid mycelial growth on PDA at 28°C with a 12-h photoperiod. The mycelia were initially hyaline and turned from gray to black after 7 days. Masses of dark spherical to oblong microsclerotia were observed after 3 days on PDA, measuring an average of 75 µm width × 114 µm length (n=30). For molecular identification, genomic DNA was extracted from mycelia and microsclerotia of a representative isolate (Yuma) using the DNeasy Plant Pro kit (Qiagen, Hilden, Germany). The internal transcribed spacer (ITS), translation elongation factor-1α (TEF-1α), calmodulin (CAL), and ß-tubulin (ß-TUB) regions were amplified using the primer sets, ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), MpCalF/MpCalR (Santos et al. 2020), and T1/T22 (O'Donnell and Cigelink 1997), respectively. A BLAST search of sequences revealed 98.7 to 100% identity to Macrophomina phaseolina sequences (MK757624, KT261797, MK447823, MK447918). Both morphological and molecular characteristics confirmed the fungus as M. phaseolina (Holliday and Punithaligam 1970). Sequences were submitted in the GenBank under accession numbers OP599770 (ITS), OP690156 (TEF-1α), OP612814 (CAL), and OP690157 (ß-TUB). Pathogenicity assay was performed on 9-week-old stevia plants (var. SW2267), grown in 4-inch planters in the greenhouse. The inoculum was made from a 14-day-old culture of M. phaseolina grown in conical flasks (250 ml) in potato dextrose broth at 28°C. Mycelial mats of the fungus were blended in 250 ml of sterile distilled water, filtered through four layers of cheesecloth, and then calibrated to 105 microsclerotia/ml using a hemocytometer. Twenty healthy plants were inoculated by soil drenching 50 ml of the inoculum per pot. Soil drenching using sterile distilled water was done on 5 non-inoculated control plants. Plants were maintained in the greenhouse at 28 ± 3°C with 12 h photoperiod. After 6 weeks, necrosis at the base of petioles and chlorosis of the leaves, followed by wilting were noticed on all 20 inoculated plants, whereas all the 5 control plants remained healthy. The fungus was reisolated and identified as M. phaseolina based on the morphology and sequences of ITS, TEF-1α, CAL and ß-TUB regions. Although M. phaseolina has been reported earlier on stevia in NC, USA (Koehler and Shew 2018), this is a first report from AZ, USA. M. phaseolina is known to be favored by high soil temperatures (Zveibil et al. 2011), thus represents a potential threat to stevia production in AZ, USA in coming years.

First Report of Powdery Mildew Caused by Golovinomyces latisporus on Helianthus annuus in the Arizona.

Helianthus annuus, known as the common sunflower, is an annual plant indigenous to the United States. The crop is grown for its edible oil, seeds, and as an ornamental. In November 2021, powdery mildew-like signs and symptoms were observed on sunflower in a house garden located at Fortuna Foothills, Yuma County, AZ (32.6725°N, 114.4329°W). Signs of powdery mildew included white blotches of amphigenous and caulicolous mycelia. Initially, signs appeared as circular spots that expanded over the entire leaf and were also observed later on petioles and stems. Fungal hyphae were branched, septate, and with nipple-shaped appressoria. Foot cells of conidiophores were erect, cylindrical, and followed by one to three short cells bearing conidia. The conidiophores were hyaline, straight, cylindrical and produced short chains of up to four immature conidia. Conidia were ovoid to ellipsoid, seldom cylindrical, without-fibrosin bodies and measured 25 to 40 µm in length (mean= 34 µm) and 16 to 24 µm in width (mean= 18.6 µm) (n = 10), with an average length: width ratio of 1.8. The germination of conidia was Euoidium type with short germ tube. Chasmothecium formation was not detected. As the disease progressed, the infected leaves became wilted and senesced. The morphological characteristics of this fungus were in accordance with those described for G. latisporus (Braun and Cook, 2012; Qiu et al., 2020). For molecular identification, genomic DNA was isolated from fungal colonies using the DNeasy Plant kit (Qiagen). The internal transcribed spacer (ITS), large ribosomal subunit (28S), intergenic spacer (IGS), beta- tubulin (TUB2) and chitin synthase 1 (CHS1) regions were amplified using the primer sets, ITS5/ITS4 (White et al., 1990), LSU1/LSU2 (Scholin et al., 1994), IGS-12a/NS1R (Carbone and Kohn, 1999), TubF1/TubR1 and gCS1a1/gCS1b (Qiu et al., 2020). Sequences were submitted in the GenBank under accession numbers OP160535 (ITS), OP153874 (28S rDNA), OP160534 (IGS), OP168959 (TUB2) and OP168960 (CHS1). A BLAST search revealed 98.7 to 100-% identity to G. latisporus sequences (MK452603, NG_068877, MK452520, MK452476, and MK452428). Phylogenetic analysis based on the combined sequence datasets of ITS+28S rDNA+IGS+TUB2+CHS1 also grouped Yuma isolate in a monophyletic clade with G. latisporus accessions from Qiu et al. (2020). A pathogenicity test was carried out by inoculating four sunflower varieties (Velvet queen, Evening sun, Skyscraper and Mammoth). Conidia from infected leaves were dusted on the leaves of 10 individually potted, five-week-old seedlings of each variety. Four seedlings of each variety were not inoculated and served as controls. The inoculated and control plants were then kept in two separate greenhouses at 25-28°C at the Yuma Agricultural Center, Yuma, AZ. Inoculated plants started showing symptoms of powdery mildew within 7 days of inoculation, while the control plants stayed healthy and disease-free. The morphological characteristics of powdery mildew fungus on the inoculated plants were identical to the isolate collected from the garden, with the same sequence following PCR as above, thus fulfilling Koch's postulates. G. latisporus has been previously reported on common sunflower from Washington and California states (Qiu et al., 2020), however, this is a first report from Arizona. Although sunflower is not a major crop in Arizona, the wild sunflower population could serve as reservoir for the spread of the disease.

Human health risk assessment: Study of a population exposed to fluoride through groundwater of Agra city, India.

Fluoride (F-), a harmful compound if present in high concentration, is typically found in groundwater. It is important to investigate the F- concentrations in groundwaters of areas where individuals use groundwater for drinking purposes. The objectives of this study were: (a) to estimate the F- exposure, and (b) to assess the non-carcinogenic risk through consumption of groundwater among urban population (different age groups) of Agra city. A total of 28 groundwater samples were collected from Agra city in May 2016, which comprised 22 samples from hand pump and 6 samples from tube wells from shallow aquifers at different sites. The F- concentrations varied from 0.90 to 4.12 mg/L with an average value of 1.88 mg/L. The results obtained reveal that about 64% of the samples exceeded the F- permissible limit of 1.5 mg/L. Nevertheless, 32% of the samples were well within the WHO drinking water guidelines and 3.5% of the samples from the groundwater were below the 1.0 mg/L threshold. The maximum estimated exposure doses were 0.69, 0.31 and 0.12 mg/kg/day for infants, children and adults, respectively. A dental fluorosis becomes evident when the results obtained are compared with an oral reference dose of 0.06 mg/kg/day. The hazard quotient (HQ) was found to be more than 1 for infants and children in all the studied areas which indicates that young consumers are more vulnerable to non-carcinogenic risk due to exposure of F-. On the other hand, the adults at about 71% of the sampled sites may be victims of non-carcinogenic risk. From the results obtained in this study, it is recommended that there be implementation of the appropriate remediation for defluoridation of water to circumvent the population from the probable health risks of F-.

Fluoride contamination, health problems and remediation methods in Asian groundwater: A comprehensive review.

In low concentration, fluoride is considered a necessary compound for human health. Exposure to high concentrations of fluoride is the reason for a serious disease called fluorosis. Fluorosis is categorized as Skeletal and Dental fluorosis. Several Asian countries, such as India, face contamination of water resources with fluoride. In this study, a comprehensive overview on fluoride contamination in Asian water resources has been presented. Since water contamination with fluoride in India is higher than other Asian countries, a separate section was dedicated to review published articles on fluoride contamination in this country. The status of health effects in Asian countries was another topic that was reviewed in this study. The effects of fluoride on human organs/systems such as urinary, renal, endocrine, gastrointestinal, cardiovascular, brain, and reproductive systems were another topic that was reviewed in this study. Different methods to remove fluoride from water such as reverse osmosis, electrocoagulation, nanofiltration, adsorption, ion-exchange and precipitation/coagulation were introduced in this study. Although several studies have been carried out on contamination of water resources with fluoride, the situation of water contamination with fluoride and newly developed technology to remove fluoride from water in Asian countries has not been reviewed. Therefore, this review is focused on these issues: 1) The status of fluoride contamination in Asian countries, 2) health effects of fluoride contamination in drinking water in Asia, and 3) the existing current technologies for defluoridation in Asia.

Quick and accurate detection of Fusarium oxysporum f. sp. carthami in host tissue and soil using conventional and real-time PCR assay.

Safflower wilt, caused by Fusarium oxysporum f. sp. carthami (Foc) is a major limiting factor for safflower (Carthamus tinctorius) production worldwide. In India alone, about 40-80% disease incidence has been reported. A rapid, efficient, specific, and sensitive diagnostic technique for Foc is therefore crucial to manage Fusarium wilt of safflower. Twenty-five isolates of F. oxysporum formae speciales infecting other crops, 17 isolates of Fusarium spp. and seven isolates of other fungal pathogens of safflower along with 75 Foc isolates were used for identification of band specific to Foc using inter-simple sequence repeat (ISSR) analysis. Out of 70 ISSR primers, the one that specifically amplified a 490 bp fragment from all the Foc isolates was selected. Sequence of the amplified fragment was utilized to design sequence characterized amplified region (SCAR) primers (FocScF/FocScR). The primer pair unambiguously and exclusively amplified a DNA fragment of approximately 213 bp in all the 75 Foc isolates. The primer set was able to detect as low as 10 pg of Foc genomic DNA using conventional PCR, while the SCAR primers when coupled with real-time qPCR demonstrated detection limits of 1 pg for Foc genomic DNA and 1000 conidia/g for soil. The assay enabled reliable diagnosis of Foc DNA in contaminated safflower fields and expedited Foc detection at 72 h post inoculation in asymptomatic seedlings. This method facilitates quick and precise detection of Foc in plant and soil samples and can be exploited for timely surveillance and sustainable management of the disease.

Secreted in Xylem Genes: Drivers of Host Adaptation in Fusarium oxysporum.

Fusarium oxysporum (Fo) is a notorious pathogen that significantly contributes to yield losses in crops of high economic status. It is responsible for vascular wilt characterized by the browning of conductive tissue, wilting, and plant death. Individual strains of Fo are host specific (formae speciales), and approximately, 150 forms have been documented so far. The pathogen secretes small effector proteins in the xylem, termed as Secreted in Xylem (Six), that contribute to its virulence. Most of these proteins contain cysteine residues in even numbers. These proteins are encoded by SIX genes that reside on mobile pathogenicity chromosomes. So far, 14 proteins have been reported. However, formae speciales vary in SIX protein profile and their respective gene sequence. Thus, SIX genes have been employed as ideal markers for pathogen identification. Acquisition of SIX-encoding mobile pathogenicity chromosomes by non-pathogenic lines, through horizontal transfer, results in the evolution of new virulent lines. Recently, some SIX genes present on these pathogenicity chromosomes have been shown to be involved in defining variation in host specificity among formae speciales. Along these lines, the review entails the variability (formae speciales, races, and vegetative compatibility groups) and evolutionary relationships among members of F. oxysporum species complex (FOSC). It provides updated information on the diversity, structure, regulation, and (a)virulence functions of SIX genes. The improved understanding of roles of SIX in variability and virulence of Fo has significant implication in establishment of molecular framework and techniques for disease management. Finally, the review identifies the gaps in current knowledge and provides insights into potential research landscapes that can be explored to strengthen the understanding of functions of SIX genes.

Arbuscular Mycorrhiza Augments Arsenic Tolerance in Wheat (Triticum aestivum L.) by Strengthening Antioxidant Defense System and Thiol Metabolism.

Arbuscular mycorrhiza (AM) can help plants to tolerate arsenic (As) toxicity. However, plant responses are found to vary with the host plant and the AM fungal species. The present study compares the efficacy of two AM fungi Rhizoglomus intraradices (M1) and Glomus etunicatum (M2) in amelioration of As stress in wheat (Triticum aestivum L. var. HD-2967). Mycorrhizal (M) and non-mycorrhizal (NM) wheat plants were subjected to four levels of As (0, 25, 50, and 100 mg As kg-1 soil). Although As additions had variable effects on the percentage of root colonized by the two fungal inoculants, each mycobiont conferred benefits to the host plant. Mycorrhizal plants continued to display better growth than NM plants. Formation of AM helped the host plant to overcome As-induced P deficiency and maintained favorable P:As ratio. Inoculation of AMF had variable effects on the distribution of As in plant tissues. While As translocation factor decreased in low As (25 mg kg-1 soil), it increased under high As (50 and 100 mg As kg-1 soil). Further As translocation to grain was reduced (As grain:shoot ratio) in M plants compared with NM plants. Arsenic-induced oxidative stress (generation of H2O2 and lipid peroxidation) in plants reduced significantly by AMF inoculation. The alleviation potential of AM was more evident with increase in severity of As stress. Colonization of AMF resulted in higher activities of the antioxidant enzymes (superoxide dismutase, catalase, and guaiacol peroxidase). It increased the concentrations of the antioxidant molecules (carotenoids, proline, and α-tocopherol) than their NM counterparts at high As addition level. Comparatively higher activities of enzymes of glutathione-ascorbate cycle in M plants led to higher ascorbate:dehydroascorbate (AsA:DHA) and glutathione:glutathione disulphide (GSH:GSSG) ratios. Inoculation by AMF also augmented the glyoxalase system by increasing the activities of both glyoxalase I and glyoxalase II enzymes. Mycorrhizal colonization increased concentrations of cysteine, glutathione, non-protein thiols, and activity of glutathione-S-transferase that facilitated sequestration of As into non-toxic complexes. The study reveals multifarious role of AMF in alleviation of As toxicity.