The Golden Potato Cyst Nematode Globodera rostochiensis Pathotype Ro1 in the Saint-Amable Regulated Area in Quebec, Canada.

The golden potato cyst nematode, Globodera rostochiensis (Wollenweber, 1923) Behren, is an economically important parasite of potato (Solanum tuberosum L. subsp. tuberosum) and is recognized as a quarantine pest internationally (2). This pest attacks potato plants and causes stunting of the haulm and the root system, leaf yellowing, and tuber yield losses (2). The pathotype scheme proposed by Kort et al. distinguishes five pathotypes (Ro1, Ro2, Ro3, Ro4, and Ro5) of G. rostochiensis using differential Solanum clones (1). Several resistance genes and quantitative trait loci (QTL) that have been identified in wild Solanum species confer resistance to different G. rostochiensis pathotypes and have been introgressed into commercial potato cultivars (2). Determining G. rostochiensis pathotype(s) is essential to implement efficient management strategies, which include using resistant potato varieties. G. rostochiensis was discovered in the municipality of Saint-Amable, Quebec (QC), Canada in 2006 (3) and was subsequently characterized (4). In this study, cysts were collected from 11 representative infested fields and confirmed to be G. rostochiensis (3). The pathotypes of these nematodes were assessed on seven differential clones (S. tuberosum subsp. tuberosum cv. Desiree, S. tuberosum × S. andigena cv. Maris Piper, S. kurtzianum hybrid 60.21.19, S. vernei hybrid 62.33.3, S. vernei hybrid 58.1642/4, S. vernei hybrid 65.346/19, and S. multidissectum hybrid P55/7) in 2007 and 2009. Briefly, in each 1-liter plastic pot containing 907 g (2 lbs) of soil (3:1 loam/grit v v-1), a single differential Solanum clone was planted and 15 cysts from 1 of 11 fields were inoculated. Five replicates were set up for each Solanum-nematode combination and the pots were arranged in a completely randomized design in a greenhouse at 22°C with a 16-h light period per day. Nine weeks after inoculation, cysts were extracted from each pot and counted. Reproduction factor (Rf) for each replicate was calculated (Rf = Pf/Pi; Pf is the final cyst number and Pi is the initial cyst number added to each pot). Rf values were used to categorize the differential clones into two groups, "susceptible" leading to increase in nematode numbers (Rf > 1) and "resistant" resulting in decrease in nematode numbers (Rf ≤ 1) (1). Our results in 2007 and 2009 were consistent and the pathotype of the nematodes collected from all the fields were identified as Ro1. To our knowledge, this is the first time that the pathotype of G. rostochiensis in the Saint-Amable regulated area was identified. Accordingly, potato cultivars carrying genes or QTL resistant to G. rostochiensis pathotype Ro1 can be used to reduce the nematode numbers in infested fields in the Saint-Amable area, QC. References: (1) J. Kort et al. Nematologica 23:333, 1977. (2) R. J. Marks and B. B. Brodie. Potato Cyst Nematodes: Biology, Distribution, and Control. 1st ed. CAB International, Wallingford, 1998. (3) F. Sun et al. Plant Dis. 91:908, 2007. (4) Q. Yu et al. Can. J. Plant Pathol. 32:264, 2010.