Distribution of root-knot nematode species and their virulence on vegetables in northern temperate agro-ecosystems of the Pakistani-administered territories of Azad Jammu and Kashmir

Root-knot nematodes (RKN) are yield devastating plant pathogens. Objective of this study was to investigate the distribution of RKN and their threat to vegetable production in the Pakistani-administered districts of Muzaffarabad, Hattian Bala and Neelum. A survey in more than 130 vegetable fields during summer 2012, 2013 and 2014 revealed a remarkable occurrence and prevalence of RKN in many vegetable crops. RKN were found in 64 % of the fields in Muzaffarabad, 30 % of the fields in Hattian Bala and 24 % of the fields in Neelum. Okra was infested on 26 sites with a gall index range of 3-10, tomato on 26 sites with a gall index of 2-10, cucumber at 13 sites with a gall index of 3-9 and eggplant at 11 sites with a gall index of 3-9. Other hosts infested by RKN included mint, beans, cucurbits and peach. Identification of RKN species was performed morphologically by perineal patterns, by PCR using primers for the IGS2 region or SCAR primers, and some by sequencing of a COI gene fragment. The RKN of this temperate region were mostly identified as tropical species. M. incognita was found in 83 % of the tested fields followed by M. javanica (76 %) and M. arenaria (36 %). M. javanica was the predominant species in Muzaffarabad and Hattian Bala. This is the first comprehensive study on the presence of tropical RKN species in the temperate region of Azad Jammu and Kashmir, Pakistan, and their virulence on vegetable crops.