According to previous surveys, the area of native
grasslands in northern China where toxic weeds
occur at a harmful level is 333 million hectares, with
the major threat being locoweed, accounting for
about 33 percent of the affected area (figure 1)
(Zhao et al. 2005). More recently, the locoweedinfested
areas have been expanding (Zhao et al.
2005), and sustainability of livestock production in
these critical grassland regions is in peril.
The primary toxic compound in locoweed is the
indolizidine alkaloid swainsonine (Molyneux et al.
1989), which is now believed to be produced by the
endophyte Undifilum oxytropis (Pryor et al. 2009)
and which was previously referred to as Embellisia
oxytropis (Braun et al. 2003, Ralphs et al. 2008, Lu
et al. 2009). Interestingly, Broquist et al. (1985)
reported production of swainsonine and slaframine
(both indolizidine alkaloids with similar biosynthetic