Intra-racial genetic variation of Ditylenchus dipsaci isolated from garlic in Ontario as revealed by random amplified polymorphic DNA analysis

The stem and bulb nematode (Ditylenchus dipsaci) was found in garlic from across Ontario in a survey conducted in 2011. Nematodes from the survey were extracted from garlic samples and the identification of Ditylenchus species was established using morphological and molecular methods. The genetic variation of 90 populations collected from different regions in the province was studied using the random amplified polymorphic DNA (RAPD) method. One population from onion and one population of D. destructor were included for comparison. Simple matching coefficiency and hierarchical cluster analysis were performed on the polymorphisms to demonstrate the intra-racial, intra-species and interspecies relationships. Genetic variation was detected in the D. dipsaci populations isolated from garlic in Ontario. All the D. dipsaci populations were separated into two distinct clusters: a small cluster consisting of 19 populations from counties in the southern part of the province, and a large cluster of 71 populations mostly from the eastern region but which also included a few populations from the southern western and northern regions of the province. The average similarity coefficiency among populations of D. dipsaci isolated from garlic was 82%. The grouping of the two distinct clusters seems to suggest that there were two separate introductions of D. dipsaci in Ontario. This is the first report of intra-racial genetic variations of D. dipsaci. © 2013 The contribution of Y. Qiao, M. Zaidi, A. Badiss and Q. Yu.