First Report of a Highly Damaged Potato Crop From Serbia Caused by Meloidogyne incognita

In 2014, a potato (Solanum tuberosum var. Kuroda) crop exhibiting 70% galling of tubers was observed in Bački Vinogradi, Vojvodina Province, Serbia. Potatoes had been grown every year for 5 years on this 1-ha site of sandy soil; tomatoes had been grown before that. In 2014, yield loss was observed for the first time at this location. Yield loss was approximately 20 tons/ha due to external galling and internal necrosis just below the skin, caused by an unknown root-knot nematode (Meloidogyne sp.). Galls were large, easily noticeable and scattered densely across the tuber surface. Adult females were visible just below the surface as white, pear-shaped bodies surrounded by a yellowish layer of host tissue. Symptoms of stunted and wilted plants were not detected despite heavy tuber infestation. The galls produced on potato tubers resembled damage caused by M. chitwoodi and M. fallax. Morphological characterization of female perineal patterns was analyzed on freshly isolated females (n = 30). Morphological identification of the species based on perineal patterns indicated the nematode was M. incognita. Species identification was further confirmed by isozyme phenotyping by esterase and malate dehydrogenase of 20 young egg-laying females (Strajnar et al. 2009). The isozyme patterns were I1 and N1, typical for M. incognita. Species identification was confirmed by mtDNA sequence analysis. A region of mtDNA was amplified with primers C2F3 and 1108 (Powers and Harris 1993), cloned, sequenced (GenBank Accession No. LN864824). Similarity of the sequence to other M. incognita sequences (99.9% identity) in GenBank and phylogenetic analysis confirmed the species identification. Meloidogyne incognita is globally the most rapidly spreading plant-parasitic nematode (Bebber et al. 2014), and is often referred to as one of the most damaging Meloidogyne species. It is found worldwide in tropical and subtropical regions as it prefers a warm habitat. In temperate regions, M. incognita is usually found in greenhouses. The investigation of distribution of Meloidogyne spp. in Serbia dates back to the 1980s (Jovičić and Grujičić 1986). During this intensive survey, widespread occurrence of M. incognita was observed, with M. incognita found in 18 localities. Meloidogyne incognita has been reported on tomatoes, cucumbers, and carnations in greenhouses and on field-grown tomatoes and peppers. Damage by M. incognita has only been reported on field-grown sunflower and tobacco plants. The severe damage reported here was a result of favorable conditions for this species leading to high infestation probably due to the combination of sandy soil and recently experienced warmer summers. There have been other reports of M. incognita found outside of greenhouses in open fields of temperate regions as well (Castillo and Jiménez-Díaz 2003). However, the severity of the damage from M. incognita observed on potato in the continental climate of the Balkan Peninsula has never been seen before. We anticipate that climate change and increased temperatures will result in significantly greater damage to potato by M. incognita in the future and may become an emerging problem for the Balkan Peninsula and other temperate regions of the world. bac