UNTRANSFORMED PLANTS RESISTANT TO HYGROMICIN

[Jose Alfredo Iglesias Jimenez]

I have transformed leaf disks of N. tabacum with A. 
tumefaciens At650 strain harboring plasmid pSGH which contains the 
hygromicin resistance gene (hph) under the control of 35S promoter. 
Tranformants were selected on 25 mg of hygromicin per liter. 
However, the controls (untraformed leaves) formed callus. Also, A. 
tumefaciens grows alone on this media culture.
Anyone knows about some endogenous resistance of plants to hygromicin? 
What is the best concentration for hygromicin selection for A. 
tumefaciens and N. tabacum?

Thanks a lot in advance! 

JOSE IGLESIAS
Student of biology
UIS, Bucaramanga Col.