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Maize is the third most vital global cereal, playing a key role in the world economy and plant genetics research. Despite its leadership in production, maize faces a severe threat from banded leaf and sheath blight, necessitating the urgent development of eco-friendly management strategies. This study aimed to understand the resistance mechanisms against banded leaf and sheath blight (BLSB) in maize hybrid “Vivek QPM-9”. Seven fungicides at recommended doses (1000 and 500 ppm) and two plant defense inducers, salicylic acid (SA) and jasmonic acid (JA) at concentrations of 50 and 100 ppm, were applied. Fungicides, notably Azoxystrobin and Trifloxystrobin + Tebuconazole, demonstrated superior efficacy against BLSB, while Pencycuron showed limited effectiveness. Field-sprayed Azoxystrobin exhibited the lowest BLSB infection, correlating with heightened antioxidant enzyme activity (SOD, CAT, POX, β-1,3-glucanase, PPO, PAL), similar to the Validamycin-treated plants. The expression of defense-related genes after seed priming with SA and JA was assessed via qRT-PCR. Lower SA concentrations down-regulated SOD, PPO, and APX genes but up-regulated CAT and β-1,3-glucanase genes. JA at lower doses up-regulated CAT and APX genes, while higher doses up-regulated PPO and β-1,3-glucanase genes; SOD gene expression was suppressed at both JA doses. This investigation elucidates the effectiveness of certain fungicides and plant defense inducers in mitigating BLSB in maize hybrids and sheds light on the intricate gene expression mechanisms governing defense responses against this pathogen.

Since time immemorial organic amendments have been an important strategy for improving soil fertility and suppressing a wide range of soil-borne pathogens. Biochar, a charcoal-like amendment has true potential in managing phytopathogens with an eco-friendly approach. It is produced by subjecting plant materials and agricultural waste to high temperatures of around 900°C in limited oxygen conditions. Biochar is considered to be an excellent carbon sequester and has an undeniably imperative role in improving soil properties. Biochar has innumerable applications in the remediation of environmental pollutants by immobilizing heavy metals such as Cadmium and Arsenic and degradation of dyes and pesticides. One of the most significant advantages of biochar in addition to mitigating environmental pollution is effectively managing plant pathogens by altering soil physical and chemical properties and promoting antagonistic microorganisms. Biochar directly suppresses plant pathogens by priming plant defense mechanisms. For instance, sugarcane bagasse biochar remediates Cd from contaminated soil, and citrus wood biochar induces systemic resistance against Botrytis cinerea in host-Lycopersicon esculentum, Capsicum annuum L. cv. Maccabi and Fragaria ananassa. Nevertheless, it is essential to acknowledge its limitations, such as the potential to absorb and enhance the residual activity of harmful chemicals. Further research is needed to develop a deeper understanding of biochar’s properties and mechanisms for more effective results. Advanced techniques like meta-transcriptomics and metaproteomics hold the potential to provide invaluable insights into this field. The review provides a comprehensive overview of current information regarding biochar, covering its production techniques and highlighting its agricultural benefits, with a particular focus on its role in plant disease management. Furthermore, the associated risks and concerns are also discussed.

Maydis leaf blight is a significant disease of maize caused by Bipolaris maydis race T, O and C. Molecular mechanisms regulating defense responses in non-CMS maize towards race O fungus are not fully known. In the present investigation, comparative transcriptome profiling was conducted on a highly resistant maize genotype SC-7-2-1-2-6-1 against a standard susceptible variety CM 119 at 48 h post inoculation (h PI) along with non-infected control. mRNA sequencing generated 38.4 Gb data, where 9349602 reads were mapped uniquely in SC-7, whereas 2714725 reads were mapped uniquely in CM-119. In inoculated SC-7, the total number of differentially expressed genes (DEGs) against control was 1413, where 1011 were up-regulated, and 402 were down-regulated. In susceptible inoculated genotype CM 119, the number of DEGs against control was 2902, where 1703 were up-, and 1199 were down-regulated. DEGs between inoculated resistant and susceptible genotypes were 10745, where 5343 were up-, and 5402 were down-regulated. The RNA-seq data were validated using RT-qPCR. The key findings are that SC-7 poses a robust plant signaling system mainly induced by oxidation–reduction process and calcium-mediated signaling. It regulates its fitness-related genes efficiently, viz., aldolase 2 gene, isopropanoid, phyto hormones, P450 cytochrome, amino acid synthesis, nitrogen assimilation genes etc. These findings showed more transcriptional changes in the SC-7 genotype, which contains many defence-related genes. They can be explored in future crop development programmes to combat multiple maize diseases. The current finding provides information to elucidate molecular and cellular processes occurring in maize during B. maydis race O infection.

In mango pickle industry, a significant quantity of mango seed kernels is discarded as solid wastes. These seed kernels can be an ideal source for obtaining extracts rich in bioactive polyphenolic compounds with good antioxidant properties. The potential of mango kernel phenolic extract (MKPE) was investigated as a natural and effective antimicrobial agent for controlling major postharvest fungal pathogen infections, a significant threat to global food supply chains. Fungal pathogens contribute to the deterioration of fruits, vegetables, and grains during storage and transportation, leading to economic losses and compromised food safety. MKPE was obtained from pickling variety 'Ramkela' raw mango kernels, and its phenolic composition was characterized using LC–MS. The in vitro antifungal activity of MKPE against Botrytis cinerea, Colletotrichum gloeosporoides, and Rhizopus stolonifer was evaluated in vitro. A concentration-dependent inhibition of fungal radial growth against all three pathogens was observed, exhibiting the potential of MKPE as a valuable natural resource for addressing postharvest losses caused by fungal pathogens. The extraction process yielded a total phenolic content of 2128 mg GAE/100 g. Major polyphenolic bioactive compounds present were mangiferin, quercetin, and rhamnetin. The in-vitro antimicrobial assay showed reduction in the radial growth and inhibition percent of the pathogens. EC50 values of MKPE for B. cineria, C. gloeosporoides, and R. stolonifer was found to 364.17, 963.8 and 926 ppm, respectively. Our results demonstrate an economical, sustainable, and eco-friendly approach to manage post-harvest diseases rendered by fungi using mango MKPE from pickling industry waste.

The pursuit of creating safe and efficient pesticides remains an ongoing aspiration. Recently, the potential efficacy of metal nanoparticles against diverse phytopathogens has come to light. Commonly used methods, viz. chemical and physical means of nanoparticle synthesis are associated with a range of drawbacks. Fortunately, the biological synthesis method ensures safe and non-toxic nanoparticles. The present study was carried out during 2022–23 at ICAR- Indian Agricultural Research Institute, New Delhi, which documented the successful synthesis of copper nanoparticles (CuNPs) utilizing the supernatant of potent fungal biocontrol agents, viz. Trichoderma virens and Chaetomium globosum. The reduction in the size of copper was determined by UV-Vis spectroscopy. The change in colour of the reaction mixture confirmed the reduction in the size of particles. Characterization using TEM measured spherical CuNPs of the size range 8 to 100 nm depending on the CuSO4 concentration used. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR) unveiled the presence of several functional groups that plays pivotal role in reducing and stabilizing particle size. The in vitro assay conclusively demonstrated the effectiveness of biosynthesized CuNPs, with significant inhibition at a concentration of 10 µg/ml in the case of Xanthomonas euvesicatoria and at 50 µg/ml in the case of Enterobacter cloacae. Our study marks the first instance of synthesizing CuNPs through the utilization of two aforesaid fungal species holding significant promise for antibacterial applications.

Maize or corn (Zea mays L.) is the third most important cereal crop in the economy of agriculture. Banded leaf and sheath blight (BLSB) caused by Rhizoctonia solani (= R. solani f. sp. sasakii) is one of the highly devastating soil-borne diseases of maize in South and Southeast Asia. Although the use of resistant varieties is preferred as an eco-friendly and cheapest approach to disease management, unfortunately, no true genetic sources of BLSB resistance are available in maize. Hence, chemically induced resistance in the host plant is considered an alternative strategy against many crop diseases. The present study investigated the basis of BLSB resistance in maize hybrid variety Vivek QPM-9 by seed priming with two plant defense inducers, viz., salicylic acid (SA) and jasmonic acid (JA). Higher concentrations (100 ppm) of SA and JA were significantly more effective against R. solani than the lower concentrations (75 and 50 ppm) in vitro. The study found that the application of SA and JA as exogenous pretreatment resulted in improved seed germination, increased seedling weight, and enhanced overall plant growth. During the Kharif season (June–October) in both 2020 and 2021, under in vivo conditions in a net house, the application of SA at 100 and 75 ppm and JA at 100 ppm resulted in a significant decrease in the percent disease index (PDI) of 46.79%, 47.05%, and 48.85%, respectively. Both plant defense inducers elevated the activity of the enzymes superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) in maize at higher concentrations of 100 ppm. Seed priming with a high concentration of the inducers was more effective in suppressing the disease and increasing grain yield under the controlled condition of the net house. The study shows the scope of using need-based fungicides with a reduced amount in the management of fungal diseases of maize by adopting a plant defense inducer-mediated host resistance approach.

Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED50 for the fungi under study ranged from 43 to 56 μg ml−1, and a significant inhibition was observed at a low dose of 20 μg ml−1 under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L−1 of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L−1 and 500 mg L−1) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L−1 rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L−1 reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.

Bio-control agents are the best alternative to chemicals for the successful management of plant diseases. Among them, Trichoderma is commonly used as a biological control agent in plant disease management due to its ability to suppress soil-borne plant pathogens. In the present study, 20 Trichoderma asperellum isolates were collected from different geographical locations and confirmed using morphological characteristics and molecular phylogenetic inferences based on combined ITS and β-tubulin sequences. All twenty isolates were screened for their antagonism against the collar rot pathogen under in vitro and in planta conditions. The isolates were evaluated through dual culture and volatile methods in an in vitro study. Isolate A10 inhibited the test pathogen Agroathelia rolfsii at 94.66% in a dual culture assay and 70.95% in a volatile assay, followed by the isolates A11 and A17, which recorded 82.64% and 81.19% in dual culture assay and 63.75% and 68.27% in the volatile assay respectively. An in planta study was conducted under greenhouse conditions in tomato var. pusa ruby by pre- and post-inoculation of T. asperellum isolates in the A. rolfsii infected soil to evaluate their antagonistic potential against the disease. The A10 isolate was found effective under both pre- and post-inoculation conditions, with a disease inhibition percent of 86.17 and 80.60, respectively, followed by the isolates A11 and A17, which exhibited inhibition of 77.80% and 75.00% in pre-inoculation and 72.22% and 69.44% in post-inoculation, respectively. Further, biochemical analysis was conducted to determine the specific activity of hydrolytic enzymes produced by T. asperellum during interaction with A. rolfsii. We found that isolate A10 produces more hydrolytic enzymes with the specific activity of 174.68 IU/mg of β-1,3 glucanase, 183.48 IU/mg of β-1, 4 glucanase, 106.06 IU/mg of protease, followed by isolate A17, A11 respectively. In GC-MS analysis, we observed maximum anti-microbial volatile organic compounds from the isolate A10, including 2H-Pyran-2-one (17.39%), which was found to be most abundant, followed by dienolactone (8.43%), α-pyrone (2.19%), and harziandione (0.24%) respective retention time of 33.48, 33.85, 33.39, and 64.23 min, respectively, compared to other isolates. In the TLC assay, we observed that a greater number of bands were produced by the A10 and A17 isolates in the Hexane: Ethyl Acetate (1:1) solvent system than in the 9:1 solvent system, which represents the presence of major metabolites in the ethyl acetate extract.

Maydis leaf blight (MLB) incited by Bipolaris maydis occurs in most of the maize growing regions. Present study revealed morphological divergence among 74 isolates of B. maydis collected from geographically distant places of India. Based on morpho-cultural features clustered by R software, 25 representative isolates of B. maydis were used for race identification. The internal transcribed spacer (ITS) sequence further confirmed the isolates as B. maydis. In recent concept, variation in disease incidence and infectivity denotes genetic shift in the pathogen or introduction of new pathogenic race(s) through germplasm exchange. For unveiling Indian race(s) of B. maydis, present exploration was made. Four genetically divergent maize genotypes with cytoplasmic male sterility (CMS), viz. -C (MGU- 161QPV-C), -T (MGU- 345PV-T), -S (MGU-150Q-S) and CM-119 (fertile cytoplasm) were assessed using 25 isolates of B. maydis during kharif 2018-19 at ICAR-IARI, New Delhi. The genotype MGU-161QPV-C associated with CMS-C was highly resistant followed by MGU-345PV-T (CMS-T) and MGU-150Q-S (CMS-S), whereas CM-119 showed high susceptibility. Present outcome confirmed prevalence of race 'O' of B. maydis in India and eliminated uncertainty about occurrence of other races, i.e. T and C.

Banded leaf and sheath blight (BLSB) of maize (Zea mays L.) caused by Rhizoctonia solani f. sp. sasakii is one of the most important yield-limiting factors faced by growers in India. Therefore, attempts were made to identify promising suitable bioagents for the management of BLSB of maize. Present study was carried out to check the efficacy of two bioformulations, viz. Pusa Th3 (Trichoderma harzianum) and Pusa Cg2 (Chaetomium globosum) against BLSB in the Vivek QPM-9 cultivar under field conditions during kharif 2018 and 2019 using seven different treatments. All the treatments significantly reduced the disease incidence and contributed higher yield of maize as compared to positive control. The lowest per cent disease index (37.87 and 53.17%) was recorded in case of both seed treatment and foliar spray with T. harzianum. It gave 40.39% disease control and also increased the yield up to 28.47% over unprotected plot. It was concluded that BLSB disease can be managed by seed treatment with T. harzianum @2 g/kg seed, followed by one spray of T. harzianum @0.1% at 30 days after sowing. Sustainable ecofriendly disease management options identified in the study can help maize growers not only in safeguarding the crop but also increase cost: benefit ratio. In addition, the results indicated that bio formulation of Pusa Th3 can be used to substitute chemical fungicides especially in controlling BLSB

Tilletia indica is a quarantine fungal pathogen that poses a serious biosecurity threat to wheat-exporting countries. Acquiring genetic data for the pathogenicity characters of T. indica is still a challenge for wheat breeders and geneticists. In the current study, double digest restriction-site associated-DNA genotyping by sequencing was carried out for 39 T. indica isolates collected from different locations in India. The generated libraries upon sequencing were with 3,346,759 raw reads on average, and 151 x 2 nucleotides read length. The obtained bases per read ranged from 87 Mb in Ti 25 to 1,708 Mb in Ti 39, with 505 Mb on average per read. Trait association mapping was performed using 41,473 SNPs, infection phenotyping data, population structure, and Kinship matrix, to find single nucleotide polymorphisms (SNPs) linked to virulence genes. Population structure analysis divided the T. indica population in India into three subpopulations with genetic mixing in each subpopulation. However, the division was not in accordance with the degree of virulence. Trait association mapping revealed the presence of 13 SNPs associated with virulence. Using sequences analysis tools, one gene (g4132) near a significant SNP was predicted to be an effector, and its relative expression was assessed and found upregulated upon infection.

Bipolaris maydis is pathogen of maize which causes maydis leaf blight disease. In India major losses occur due to the B. maydis race “O” pathogen, whereas in other parts of the world, major losses are due to the race “T” pathogen. In the present study, we conducted an in planta transcriptomics study of the B. maydis race “O” pathogen after infection on non-CMS maize resistant and susceptible genotypes by mRNA sequencing to understand the molecular basis of pathogenicity for better management of the pathogen. Approximately 23.4 GB of mRNA-seq data of B. maydis were obtained from both resistant and susceptible maize backgrounds for fungus. Differentially expressed genes (DEGs) analysis of B. maydis in two different genetic backgrounds suggested that the majority of highly DEGs were associated with mitochondrial, cell wall and chitin synthesis, sugar metabolism, peroxidase activity, mitogen-activated protein kinase (MAPK) activity, and shikimate dehydrogenase. KEGG analysis showed that the biosynthetic pathways for secondary metabolism, antibiotics, and carbon metabolism of fungus were highly enriched, respectively, in susceptible backgrounds during infection. Previous studies in other host pathogen systems suggest that these genes play a vital role in causing disease in their host plants. Our study is probably the first transcriptome study of the B. maydis race “O” pathogen and provides in-depth insight of pathogenicity on the host.

Plant growth-promoting endophytic microbes have drawn the attention of researchers owing to their ability to confer fitness benefits in many plant species. Here, we report agriculturally beneficial traits of rice-leaf-adapted endophytic Microbacterium testaceum. Our polyphasic taxonomic investigations revealed its identity as M. testaceum. The bacterium displayed typical endophytism in rice leaves, indicated by the green fluorescence of GFP-tagged M. testaceum in confocal laser scanning microscopy. Furthermore, the bacterium showed mineral solubilization and production of IAA, ammonia, and hydrolytic enzymes. Tobacco leaf infiltration assay confirmed its non-pathogenic nature on plants. The bacterium showed antifungal activity on Magnaporthe oryzae, as exemplified by secreted and volatile organic metabolome-mediated mycelial growth inhibition. GC-MS analysis of the volatilome of M. testaceum indicated the abundance of antimicrobial compounds. Bacterization of rice seedlings showed phenotypic traits of MAMP-triggered immunity (MTI), over-expression of OsNPR1 and OsCERK, and the consequent blast suppressive activity. Strikingly, M. testaceum induced the transcriptional tradeoff between physiological growth and host defense pathways as indicated by up- and downregulated DEGs. Coupled with its plant probiotic features and the defense elicitation activity, the present study paves the way for developing Microbacterium testaceum-mediated bioformulation for sustainably managing rice blast disease.

[This corrects the article DOI: 10.1371/journal.pone.0167702.].

Endophytes are symptomless fungal or bacterial microorganisms found in almost all living plant species reported so far. They are the plant-associated microbes that form symbiotic association with their host plants by colonizing the internal tissues, which has made them valuable for agriculture as a tool in improving crop performance. Many fungal endophytes produce secondary metabolites such as auxin, gibberellin etc that helps in growth and development of the host plant. Some of these compounds are antibiotics having antifungal, antibacterial and insecticidal properties, which strongly inhibit the growth of other microorganisms, including plant pathogens. This article reviews the endophyte isolated from different plants, mode of endophytic infection and benefits derived by the host plant as a result of endophytism.

In order to screen maize genotypes for resistance to post-flowering stalk rot (PFSR) complex caused by Macrophomina phaseolina (Tassi) Goid and Fusarium verticilloides (Sacc) Nirenberg under field conditions, toothpick method was used for creating artificial epiphytotics. In this study, 34 maize inbred lines were screened in field by toothpick method of inoculation. Of these accessions, representative 20 maize genotypes were screened by two new methods of inoculation of the cut stems under laboratory condition. Split stems were inoculated in the first method and un-split stems were inoculated by toothpick method in the second. The split method produced recordable data within 15 days of post-inoculation (DPI) where as the un-split stem inoculation method produced result at 20 DPI. Both the new techniques employed in the laboratory were faster in producing results as compared to the field screening of maize genotypes by the standard toothpick method which needs about 40 days for expression of PFSR symptoms. Split open method was better than the un-split method of cut stem inoculation in vitro. A new scale ranging from 1 to 16 cm was developed based on the existing 1-9 scale of PFSR for scoring disease severity in vitro.

A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat-Triticum aestivum, T. durum and T. dicoccum were screened sequentially at multiple disease hotspots, during the 2011-14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.