DE-NOVO INDUCTION OF ADVENTITIOUS ROOTS IN EXCISED SHOOTS OF TOMATOES BY FUMONISIN B-1, A METABOLITE OF FUSARIUM-MONILIFORME

The de novo induction of roots in tomatoes (Lycopersicon esculentum) Mill. cvs. ''Early-pak-7,'' ''Ace,'' ''Better Boy,'' ''Roma,'' and ''Parks' Whopper'') by fumonisin B1, a mycotoxin produced by Fusarium moniliforme J. Sheld., was studied. In graded dosages of fumonisin B1, detached stems of the cultivars ''Ace,'' ''Better Boy,'' and ''Roma'' were induced to produce calluses and roots earlier than controls. The cultivar ''Ace'' was especially responsive to this mycotoxin, and following a single application, callus initiation was observed to occur within a 24-48-h period and roots were produced as early as 72 h with 10 mug/shoot or as late as 96 h with low dosages. The control plants of all cultivars were completely negative for a rooting response during this time. Some cultivars treated with fumonisin B1 showed either no response or developed signs of phytotoxicity. Those cultivars that were stimulated to produce roots did not show signs of phytotoxicity, except at dosages of 0.5 mg/plant and higher. One cultivar did not show any signs of phytotoxicity nor was it induced to root. The ability of fumonisin B1 to affect the accumulation of calcium in other systems, and its structural similarity to sphingosine suggest that the induction of adventitious roots may be a calcium-dependent process.