Stem rot of jute (Corchorus spp.): New insight on its causal organisms

Abstract

Stem rot disease is a major threat to the successful cultivation of jute (Corchorus spp.). Although Macrophomina phaseolina is the causal agent attributed to this disease, in the present study we documented the involvement of several pathogens. Disease samples were collected from West Bengal, a major jute-growing state in India and six different types of symptoms were observed under field conditions. Isolated pathogens (n = 387) produced four types of colonies resembling growth patterns of Colletotrichum, Diaporthe, Lasiodiplodia and Macrophomina. Based on pigmentation on the reverse side of plates, Diaporthe-and Lasiodiplodia-type colonies formed two subgroups each. However, no correlation could be established between types of disease symptoms and the associated pathogens. While Colletotrichum was prevalent in the Coochbehar district, the spatial distribution of the other pathogens was random. Internal transcribed spacer (ITS) of rDNA and translation elongation factor 1-α (TEF) genes from two representative isolates from each of six morphogroups were amplified and sequenced. Phylogenetic trees were generated based on these sequences, which suggested that seven fungal pathogens belonging to four genera (Colletotrichum, Diaporthe, Lasiodiplodia and Macrophomina) were involved with stem lesions of jute. Three recommended fungicides (carbendazim, hexaconazole and tebuconazole) were tested against the selected fungal pathogens and all were found effective in suppressing their growth in vitro.