Zakira Naureen

The taxonomic placement of Schweinfurthia has been debated, with traditional classifications placing it in Scrophulariaceae while molecular evidence suggests affinity to Plantaginaceae. We sequenced and analyzed complete chloroplast genomes of Schweinfurthia papilionacea ( 153,238 bp) and S. imbricata (153,206 bp) to resolve this taxonomic uncertainty. Both genomes exhibited typical quadripartite structure with large single-copy regions (LSC: 83,703 − 83,769 bp), small single-copy regions (SSC: 18,087 − 18,089 bp), and inverted repeat regions (IRa/IRb: 25,680 − 25,723 bp each). We identified 132 - 133 unique genes in each species, including 88 protein-coding genes, 36 - 37 tRNA genes, and 4 rRNA genes. Phylogenetic analysis using maximum likelihood and Bayesian inference methods with 42 taxa strongly supported (bootstrap support > 95%, posterior probability > 0.95) the placement of Schweinfurthia within Plantaginaceae, sister to the Antirrhineae tribe. Comparative genomic analysis revealed 98.7% sequence similarity between the two Schweinfurthia species and identified 10 variable sites. Codon usage analysis showed preference for A/T-ending codons (64.2% in S. papilionacea, 64.8% in S. imbricata). These comprehensive chloroplast genomic data provide definitive molecular evidence supporting the transfer of Schweinfurthia from Scrophulariaceae to Plantaginaceae, resolving a long-standing taxonomic controversy.

There is an ongoing hunt for biologically active compounds that can combat phytopathogenic fungi and improve plant growth without causing any hazards to the environment. Consequently the present study aims at deciphering the plant growth promotion and antifungal capability of Lysinibacillus sphaericus ZA9. The bacterium was previously isolated and identified in our laboratory from maize rhizosphere using 16S rRNA gene sequencing. The test bacterium L. sphaericus ZA9 was found to produce high quantity of IAA (697 μg/ mL); siderophores (195.79 μg/ mL), HCN and hydrolytic enzyme as compared to the reference strain Bacillus sphaericus Z2-7. The bacterium was also capable of solubilizing silicates (Si), phosphates (P), and potassium (K). The bacterium enhanced the seedling vigor and germination of seeds pretreated with it and promoted the shoot length of both cucumber and tomato seeds in greenhouse experiment. L. sphaericus ZA9 and its cell free culture supernatant showed varied antagonistic behavior against Alternaria alternata, Curvularia lunata, Aspergillus sp., Sclerotinia sp., Bipolaris spicifera, Trichophyton sp. Fermentation broth culture of L. sphaericus ZA9 was then used to isolate antifungal metabolites by silica column chromatography. Identification and determination of antifungal compounds was carried out by Thin-layer chromatography (TLC) followed by NMR spectroscopy. Two compounds were isolated and identified as 2-pentyl-4-quinolinecarboxylic acid (C₁₅H₁₇NO₂) which is a quinoline alkaloid and 1- methylcyclohexene which is a cycloalkene. Compound 1; 2-Penthyl-4-quinolinecarboxylic acid was found to be highly antagonistic against most of the fungi tested as compared to the bacterium itself. Its activity was comparable to that of fungicide Benlate, while compound 2; 1- methylcyclohexene did not show any antifungal activity.