Virulence Assay and Morpho-molecular Characterization of Sclerotinia sclerotiorum-The Cabbage Head Rot Pathogen

Background: The cultivation of cabbage is impacted heavily due to cabbage head rot causing plant pathogen, Sclerotinia sclerotiorum. The present study was conducted to know the prevalence of cabbage head rot pathogen in Tamil Nadu and to assess its virulence. Methods: In this study, the survey was conducted on major cabbage-growing regions of Tamil Nadu. Pathogen associated with cabbage head rot was isolated and Koch’s postulates were conducted. Further the isolated pathogen was characterized morphologically and molecularly through ITS and species-specific primers. Results: Among the surveyed areas, Nanjanadu village in Nilgiris district showed the highest percent disease incidence of 45.23% compared to other regions. A total of ten S. sclerotiorum isolates (TNAU-SS-1, TNAU-SS-2, TNAU-SS-3, TNAU-SS-4, TNAU-SS-5, TNAU-SS-6, TNAU-SS-7, TNAU-SS-8, TNAU-SS-9, TNAU-SS-10) were obtained during isolation. Based on the virulence assay, TNAU-SS-5 (MZ379266) isolate showed a quicker lesion size of 3.77 cm2 in comparison to the control. The molecular conformation of pathogen was carried out using ITS 1 and ITS 4 primers targeting 18S-28S rRNA gene fragments. Furthermore, the isolates were confirmed with specific primers and identified as S. sclerotiorum.