The occurrence of cyst nematodes in agricultural fields of Southern Manitoba

Abstract

In southern Manitoba, Canada, a survey was carried out in 2012 and 2013 to determine the presence of Heteroderidae cyst-forming plant-parasitic nematodes, with a focus on the soybean cyst nematode (SCN) (Heterodera glycines). A total of 48 fields having grown soybean were sampled. A modified Fenwick elutriation-flotation technique was used to extract cysts with a 75% cyst recovery efficiency. Cyst population density averaged 0.9 cysts kg−1 soil, with a total of 65 cysts recovered. Preliminary screening of cysts, based on general body shape and vulval cone top structure, showed the presence of cysts belong to circumfenestrate, and ambifenestrate groups of cyst-forming nematodes. Limited morphological data was accessible due to poor quality or insufficient cysts for analysis; however, generated DNA sequences for nuclear rDNA ITS and D2-D3 expansion region of the 28S rRNA were obtained for four samples and matched sequences in GenBank for the cyst nematodes Cactodera milleri, C. torreyanae, C. weissi, C. estonica and unknown Cactodera species. Only one of the ambifenestrate cysts with a cone top structure of Heterodera species yielded DNA for analysis and its identification was ambiguous for soybean cyst nematode (SCN). None of the cysts were positive through SCN diagnostic PCR. Cactodera is not a pest of soybean or other crops in Manitoba. These cyst nematodes are likely to be naturally associated with weeds and grasses in the sampled fields or may be introduced from neighbouring states of the USA. Further annual surveys are needed and recommended in the near future to encompass more soybean fields and corroborate the absence of the pest.