Neocosmospora rubicola: An Unrecorded Pathogen from Pakistan Causing Potato Stem Rot

Potato (Solanum tuberosum) is one of the important staple crops over the world. Potato crop is threatening by a number of biotic stresses which not only affect plant health and yield but also the quality of the produce. Among biotic diseases, fungal stem and tuber rot are the most common diseases that cause significant loss in potato production in Punjab province, Pakistan. Neocosmospora rubicola was found as a new pathogen causing stem rot of potato in the potato growing area of district Kasur. Symptoms of the N. rubicola infected potato plants were necrotic stem lesions near the collar region. Causal organism was isolated from the infected tissues, purified and identified on the basis of morphological characters, nucleotide sequences of internal transcribed spacer region (ITS) and partial beta tubulin gene. Phylogenetic analysis was also conducted to determine the phylogenetic relationship of this species with other reported species of this genus. Pathogenic potential of the isolate was verified by artificially inoculating the spores of pathogen in healthy plants. Appearance of same symptoms and re-isolation of N. rubicola from infected tissue confirmed Koch’s pathogenicity postulates. Association of N. rubicola causing stem rot in potato is never reported before in Pakistan.