Induction and suppression of phytoalexin biosynthesis in cultured cells of safflower, Carthamus tinctorius L., by metabolites of Alternaria carthami Chowdhury.

Cell suspension cultures derived from the safflower variety US-10 respond to treatment with cell wall elicitors from either Phytophthora megasperma f.sp.glycinea or Alternaria carthami Chowdhury by producing polyacetylenic phytoalexins. These polyacetylenes were absent from the uninduced cell cultures. Low concentrations of brefeldin A, a toxin produced by A. carthami, when added to suspension-cultured safflower cells, considerably diminished the accumulation of the phytoalexins following elicitor treatment. Suppression of the synthesis of polyacetylenic phytoalexins suggests a role for brefeldin A in limiting the host range of A. carthami, the causal agent of a leaf and head blight disease in safflower.