In vitro selection with fusaric acid: a novel approach to breed for fusarium resistance in Gladiolus

In vitro selection represents a feasible method to isolate variants with improved traits. Selection in vitro for disease resistance is facilitated when well characterized toxins are used as selective agents. However the number of metabolic compound with a known role in the development of the disease is limited. The prospective to use a specific fungal metabolite as selective agent were investigated. We report on the use of fusaric acid for the selection of Fusarium-resistant plants. Before performing the in vitro selection, the possible use of fusaric acid (FA) as selective agent was evaluated by applying two assays involving shoots and callus tissue of 10 genotypes. Callus tissue could reflect only partially the Fusarium, resistance level of the genotypes while shoots cultured in presence of the toxin could reflect the real resistance of the genotype. Fusaric acid insensitive cell lines were selected form cell suspension challenged with 0.10–0.14 mM FA. The insensitivity to this toxin was retained even after the selective agent was removed. Callus originated from the cell lines grew well on a medium supplemented with 0.5 mM FA, when inoculated with a suspension of conidia the mycelial growth was significantly inhibited. Plantlets regenerated were tested with a shoot assay and half of them showed a reduced sensitivity to the toxin. Results suggest that selection of Fusarium-resistant variants through in vitro selection is a possible breeding approach. The final evaluation of the Fusarium-resistance level of the regenerated plantlets will be performed once the corms are grown to maturity