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Intensive cropping degrades soil quality and disrupts the soil microbiome. To understand the effect of rice monocropping on soil-microbiome, we used a comparative 16S rRNA metagenome sequencing method to analyze the diversity of soil microflora at the genomic level. Soil samples were obtained from five locations viz., Chamarajnagara, Davangere, Gangavathi, Mandya, and Hassan of Karnataka, India. Chemical analysis of soil samples from these locations revealed significant variations in pH (6.00–8.38), electrical conductivity (0.17–0.69 dS m−1), organic carbon (0.51–1.29%), available nitrogen (279–551 kg ha−1), phosphorous (57–715 kg ha−1) and available potassium (121–564 kg ha−1). The 16S metagenome analysis revealed that the microbial diversity in Gangavathi soil samples was lower than in other locations. The soil sample of Gangavathi showed a higher abundance of Proteobacteria (85.78%) than Mandya (27.18%). The Firmicutes were more abundant in Chamarajnagar samples (36.01%). Furthermore, the KEGG pathway study revealed enriched nitrogen, phosphorus, and potassium metabolism pathways in all soil samples. In terms of the distribution of beneficial microflora, the decomposers were more predominant than the nutrient recyclers such as nitrogen fixers, phosphorous mineralizers, and nitrifiers. Furthermore, we isolated culturable soil microbes and tested their antagonistic activity in vitro against a fungal pathogen of rice, Magnaporthe oryzae strain MG01. Six Bacillus sp. and two strains of Trichoderma harzianum showed higher antagonistic activity against MG01. Our findings indicate that metagenome sequencing can be used to investigate the diversity, distribution, and abundance of soil microflora in rice-growing areas. The knowledge gathered can be used to develop strategies for maintaining soil quality and crop conservation to increase crop productivity. [ABSTRACT FROM AUTHOR]

False smut disease of rice caused by Ustilaginoidea virens, is an emerging threat to rice cultivation worldwide due to its detrimental effects on grain yield and quality. False smut disease severity was 4.44‒17.22% during a roving survey in Kharif 2016 in the four different rice ecosystems of Karnataka, India. Further, 15 pathogen isolates representing four different ecosystems were studied for their virulence and morphometric diversity. Among the 15 strains studied, most virulent strains Uv-Gvt was selected for whole genome sequencing in Illumina NextSeq 500 platform using 2 × 150 bp sequencing chemistry. The total assembled genome of Uv-Gvt was 26.96 Mb, which comprised of 9157 scaffolds with an N50 value of 15,934 bp and 6628 protein-coding genes. Next, the comparative genomic study revealed a similar gene inventory as UV-8b and MAFF 236576 strains reported from China and Japan, respectively. But, 1756 genes were unique to Uv-Gvt strain. The Uv-Gvt genome harbors 422 putative host–pathogen interacting genes compared to 359 and 520 genes in UV-8b and MAFF 236576 strains, respectively. The variant analysis revealed low genetic diversity (0.073‒0.088%) among U. virens strains. Further, phylogenetic analysis using 250 single copy orthologs genes of U. virens revealed a distinct phylogeny and an approximate divergence time. Our study, report the genomic resource of rice false smut pathogen from India, where the disease originated, and this information will have broader applicability in understanding the pathogen population diversity. [ABSTRACT FROM AUTHOR]

Wilt disease affecting pomegranate crops results in rapid soil-nutrient depletion, reduced or complete loss in yield, and crop destruction. There are limited studies on the phytopathogen Fusarium oxysporum prevalence and associated genomic information with respect to Fusarium wilt in pomegranate. In this study, soil samples from the rhizosphere of different pomegranate plants showing early stage symptoms of wilt infection to an advanced stage were collected from an orchard situated in Karnataka, India. A whole metagenome sequencing approach was employed to gain insights into the adaptations of the causative pathogen F. oxysporum. Physicochemical results showed a drop in the pH levels, N, Fe, and Mn, and increase in electrical conductivity, B, Zn, Cl, Cu was observed in the early and intermediate stage samples. Comparative abundance analysis of the experimental samples ESI and ISI revealed an abundance of Proteobacteria phyla Achromobacter sp. 2789STDY5608625, Achromobacter sp. K91, and Achromobacter aegrifaciens and Eukaryota namely Aspergillus arachidicola, Aspergillus candidus, and Aspergillus campestris. Functional pathway predictions implied carbohydrate binding to be significant (p < 0.05) among the three experimental samples. Microbiological examination and whole microbiome analysis confirmed the prevalence of F. oxysporum in the soil samples. Variant analysis of F. oxysporum revealed multiple mutations in the 3IPD gene with high impact effects. 3-Isopropylmalate dehydratase and carbohydrate-active enzymes could be good targets for the development of antifungals that could aid in biocontrol of F. oxysporum. The present study demonstrates the capabilities of the whole metagenome sequencing approach for rapid identification of potential key players of wilt disease pathogenesis wherein the symptomatology is complex. [ABSTRACT FROM AUTHOR]