Morpho-molecular identification, characterization and management of Pythium catenulatum, the causative agent of root rot disease in Phaseolus vulgaris (common bean)

In this study, we identified and characterize a plant pathogenic isolate, collected from naturally infested bean (Phaseolus vulgaris var. Anupama) seedlings presenting root rot symptoms from an agricultural land of the Prayagraj district, Uttar Pradesh, India. Based on morphological features, growth characteristics and the ITS sequencing-based molecular data, the isolate was assumed very closed to the species of the Pythium genera. However, ITS sequencing data and the BLAST results for gene annotation clustered the identified isolate more closely to the Pythium catenulatum (p-value e-value), and therefore, confirmed as P. catenulatum. The pathogenicity assay confirmed the role of the isolate as a root rot causing pathogen. Furthermore, the isolate was tested for its growth under in-vitro conditions against several environmental parameters including temperature, pH, salt, drought and metals. The Biolog FF MicroPlate method assessed the carbon utilization profile and reported the ability of the isolate in utilizing both carbohydrates and amino acids as a primary energy source. Moreover, in-vitro colony growth inhibition assay performed with different agrochemicals (fungicides and insecticides) and the dyes determined their efficacy in suppressing the growth and development of the isolated pathogen. The dual culture assay of the isolate along with several fungal and bacterial strains confirmed the antagonistic potential of some tested microbes in delimiting the growth of the pathogen. Overall, the study provides a new sustainable, effective and eco-friendly solution for controlling the root rot pathogen.