The rapeseed meals produced in China, India and certain parts of Europe have high levels of glucosinolates, erucic acid and other anti nutritional factors. The new varieties developed in Canada in the middle of the 1970s have much lower levels of glucosinolates (<30 micromoles per gram) and erucic acid (<2%). These nutritionally superior 'double zero' varieties are commercially known as Canola

In the mid-80s new rape varieties were available to farmers which were low in both erucic acid and glucosinolates and were called 00 (double zero) rape. In recent years hybrid breeding has succeeded in significantly increasing the yields of these quality rape varieties.
Source: Oilseed rape cultivation in Germany. Boost from double-zero rape.
http://www.gmo-safety.eu/en/oilseed_rape/agriculture/47.docu.html