Gerbera is among the significant players in the global cut flower market, valued at 30 billion USD in 2023. Gerbera daisies, along with chrysanthemums are the largest segment of the cut flower market with a share of 40%. The quality and quantity of gerbera cut flower production is negatively impacted by the fungal disease powdery mildew causing a significant loss of revenue. Effects from powdery mildew infection include reduced flower quality, stunted growth, decreased flower longevity, and decreased marketability. Powdery mildew is currently controlled using fungicides which increases the cost of cut flower production and has the potential for the fungus to develop resistance to the fungicides. One strategy is to use gene editing and CRISPR technology to produce gerbera plants resistant to powdery mildew. The gene “mlo” which stands for “Mildew Locus O” plays a crucial role in the plant’s defense against powdery mildew infections. Plants with mutations in the “mlo” gene exhibit a type of broad-spectrum resistance providing protection against various strains of powdery mildew. We developed a tissue culture regeneration and transformation system for the Gerbera jamesonii cultivar ‘Flori Line Maxi Yellow’ which is sensitive to powdery mildew. The Agrobacterium tumefaciens strain GV3101 containing a binary plasmid encoding for an enhanced GFP marker gene and hygromycin selection gene was used to develop the transformation system. Young, 10mm sized in vitro leaves with part of the petiole were used as explants. A sensitivity test with the explants showed hygromycin at 7.5 mg/L was optimal for selection of callus with positive GFP expression. The next step is to regenerate GFP plants to confirm successful transformation and design CRISPR constructs to inactivate the “mlo” gene in the powdery mildew sensitive gerbera cultivar via gene editing.
