Tom Welacky, Agriculture and Agri-Food Canada

The main cause of yield and economic losses for the producer in Ontario since 1988 has been Soybean Cyst Nematode (SCN). It accounts for yield losses of three to five percent each year from 1999 to 2003. Losses to production and seed quality from SCN infestations exceed the combined losses from all other diseases by more than two times.

The project will form a basis from which to monitor any changes in SCN races and soybean variety reactions to new or alternative sources of resistance for the industry. The second objective of the project is to monitor and map SCN numbers and HG types in numerous farm fields
across Ontario.

Improvement of SCN resistance in soybean varieties through collaboration with private, public breeders and the Oil and Protein Seed Crop Committee is progressing consistently. Resistant soybean varieties tested in 2008 have 20 to 30 percent more yield than susceptible varieties on low and medium SCN infested fields. The Cooperative SCN Resistant variety development project with public and private breeders tested 37 resistant soybean varieties at two locations. The top five best yield performers had 16 to 20 percent more yield, an increase10 bushels, than the average of the 37 resistant varieties tested in 2008 at both test areas. Results are found on Table 7 of the 2009 Ontario Soybean Variety Trial publication or at http://www.gosoy.ca/table7.php.

Harrow survey results included 453 soil samples which were processed during the period of 2005 to 2008. SCN was recovered from 358 (79 percent) of these samples. HG-type tests were performed on 134 of the SCN positive samples.

The HG-type test determines the percentage that the SCN population increased on seven different soybean genetic lines containing SCN resistance under optimal conditions for SCN and over a 35 day time period. Each of the soybean lines are given an HG designation number. The SCN HG-type relates to the soybean line on which elevated SCN reproduction occurred.

In Ontario most of the SCN populations were rated as one of two HG types. PI 88788, the most common source of soybean genetic resistance to SCN, was susceptible to 27 percent of the Ontario SCN populations. Unexpectedly Peking, another source of genetic resistance, was susceptible to 15 percent of the Ontario SCN populations.