Morpho-molecular Characterization of Carrot Soft Rot Incitant, Pectobacterium carotovorum subsp carotovoroum

Abstract

Carrot is an important root vegetable which plays an important role in human health. Globally, Post harvest diseases are the major constraint in carrot production, especially soft rot which resulting in severe yield loss. Early diagnosis of these post-harvest diseases paves a way for reducing the economic losses. Carrot samples showing typical rotting symptoms were collected from markets of four different districts of Tamil Nadu and the pathogen involved were isolated. Severe carrot soft rot incidence (66.74%) was observed in samples collected from Ooty area of The Nilgiris district and the least disease incidence of (16.21%) was recorded in Perundurai of Erode district. Pathogenicity of soft rot pathogen were conducted and the virulent isolates were identified based on Percent Disease Index (PDI) showing >50% rotting falls under disease grade 9 using disease grade scale (0 to 9). The bacterial isolates (KPB-7 and OCB-5) causing soft rot were characterized using various biochemical assays where in they showed positive response for methyl red, H2S gas production, KOH and catalase tests besides showing negative response for gram’s reaction. Furthermore, molecular characterization of 16s rRNA region revealed the soft rot isolate (KPB-7) as Pectobacterium carotovorum subsp carotovorum (with an accession number OR251119).