In vitro selection of vanilla plants resistant to Fusarium oxysporum f. sp. vanillae

Fusarium oxysporum f. sp. vanillae (Fov), the most devastating pathogen of Vanilla planifolia, an important orchid used in the food industry, causes stem and root rot. Vanilla genotypes that are resistant to Fov currently do not exist, so vanilla plants that are resistant to this fungus are needed. In vitro selection offers an effective means to accomplish this objective. Resistant shoots were selected on Murashige and Skoog medium (MS) containing 8.88 µM of 6-benzyladenine and various concentrations of Fov culture filtrate (30, 40 and 50%, v/v). The control treatment (0%) was exclusively MS medium without any culture filtrate. After two 60-day selection cycles, 40 resistant shoots were obtained. In vitro, about 35% of the shoots were resistant to 50% Fov culture filtrate, while in vivo tests indicated that 26.6% of the plants had acquired resistance to the pathogen under greenhouse conditions after 9 weeks. The protocol employed in this study, which forms part of a wider genetic improvement program for this orchid, allowed Fov-resistant V. planifolia plants to be obtained within 420 days.