Molecular phylogeny, identification and pathogenicity of Rhizopus oryzae associated with root rot of mulberry in India.

Abstract

Root rot caused by a group of fungi is a serious disease in mulberry. This study aims to identify and characterize Rhizopus oryzae and other fungal species associated with root rot of mulberry in India. Rotted root samples were collected from the mulberry gardens from four states of Southern India. The majority of the isolates identified were R. oryzae, and others were saprophytic fungi, less abundant to occasional. Two methods of inoculations were tested to confirm the pathogenicity of the selected isolates and R. oryzae was found to be pathogenic on susceptible mulberry genotypes RC2 and SRDC-1. Multi gene phylogenetic analyses using the internal transcribed spacer region (ITS), actin (ACT) and translation elongation factor 1-α (TEF), identified the isolates as R. oryzae. Additionally, Ovatospora brasiliensis, Amesia nigricolor, Gongronella butleri, Myrmecridium schulzeri, Scedosporium boydii, Graphium euwallacea, Clonostachys rosea andTalaromyces spp. were also identified. This study revealed the existence of eleven species of fungi including the first report of R. oryzae and the occurrence of weak pathogens or saprophytes that are associated with the root rot of mulberry in India. This is the first report of R. oryzae causing Rhizopus rot of mulberry in India. Moreover, the occurrence of saprophytes associated with root rot of mulberry was identified. Further studies should focus more on the ability of these species to generate secondary metabolites and extracellular lytic enzymes as they are beneficial for the management of root rot disease.