Abstract
Tomato is a host plant of Orobanche species, the root parasite weeds. We found that roots of hydroponically-grown tomato produce abundant Orobanche minor seed germination stimulants. Reversed phase HPLC analysis of the root exudates revealed the presence of biologically active fractions, Ly1 (fast moving) and Ly2 (slow moving), the latter being a major fraction. Further HPLC of Ly1 on a phenyl column separated three stimulants Ly1-a, Ly1-b and Ly1-c which seem to be novel strigolactones. The same HPLC of Ly2 gave rise to Ly2-a and Ly2-b, the latter having a major biological activity. Ly2-b constitutes a wide peak with biological activity. GC/MS analysis of the Ly2-b resulted in the identification of four novel strigolactones (compounds A,B,C,D). The compound A had a molecular weight of 342, whereas the compounds B and C, D had a molecular weight of 344. These molecular weights were smaller than those of strigol and orobanchol (346).
