Diversity Assessment of Curvularia Species through Morphological, Physiological, Pathological and Metabolomic Analyses
Beena Gore
Department of Microbiology, Davangere University, Shivagangothri, Davangere- 577007, Karnataka, India.
S. Shishupala *
Department of Microbiology, Davangere University, Shivagangothri, Davangere- 577007, Karnataka, India.
*Author to whom correspondence should be addressed.
Abstract
Aims: Curvularia species are significant phytopathogens distributed worldwide. This pathogen can infect wide range of crops causing leaf spot, blights and grain mold. The present study intended to understand morphological and physiological variations among Curvularia isolates. It is also aimed at cellular and secretory metabolite profiling to assess variations.
Study Design: Morphological features, including colony and conidial characteristics on different media and physiological parameters like secretory enzymes, phytotoxicity, and metabolite production were analysed to understand variations among the isolates of Curvularia species.
Place and Duration of Study: Department of Microbiology, Davangere University, Davangere, Karnataka, from August 2021 to December 2023.
Methodology: Morphology of colony and conidial characteristics were studied on potato dextrose agar (PDA), Czapek-Dox agar (CZA), Sabouraud’s dextrose agar (SDA), and Malt extract agar (MEA) media. Secretion of amylase, cellulase and pectinase enzymes were assayed on agar plate by incorporating suitable substrate in the medium. Phytotoxicity of the isolates were evaluated on the leaves by detached leaf bioassay. Effect of the isolates on germination of sorghum seeds and seedling vigour were evaluated. Metabolite profile of cellular and secretory extracts was analysed by thin-layer chromatography and UV-Visible spectroscopy.
Results: Morphological and physiological differences were evident among the isolates of Curvularia species. Variations in colony growth of C. clavata and C. lunata isolates (PDA and MEA) and C. fallax isolates (SDA), were found. The highest colony diameter of 89±0.5 mm was shown in C. clavata DUMB 137. The least colony diameter was noticed in C. lunata DUMB 145. Differences in colony diameter were also conspicuous among the species of Curvularia. Colony morphological differences among C. clavata and C. lunata isolates were found on PDA and MEA. Distinct conidial characteristics in shape, colour and size were apparent on all the media. All Curvularia species exhibited variations in secretion of amylase and pectinase. The highest amylase Enzyme Index (EI) of 2.29 was shown by C. clavata DUMB 132 and least 0.83 by C. lunata DUMB 141. Isolates of C. clavata showed higher phytotoxic effect than C. lunata and C. fallax. Variations in the effect of Curvularia species on sorghum seed germination were found. An isolate of C. fallax was highly pathogenic on sorghum, significantly reducing seedling vigour index to 806 as against control (1704). A distinct metabolite profile among isolates of Curvularia was detected. Unique compounds with different absorption maxima were detected by UV-Visible spectroscopy.
Conclusion: Inter- and intra-specific variations in the morphology and physiology of Curvularia species were evident. These variations aid in the identification of the species and contribute to a deeper understanding of the diversity and adaptability of Curvularia species on different hosts. Such analyses would help in chemotaxonomy, bio-surveillance and management of diseases caused by Curvularia.
Keywords: Curvularia, Colony morphology, seed germination, seedling vigour, Thin-layer chromatography, UV- visible spectroscopy