Evaluation of 21 different media on shoot regeneration in 11 cultivars of citrus using juvenile tissue

Citrus is one of the most important global fruit crops, with oranges accounting for more than half the total production. Citrus can be genetically engineered for improved traits, but the process is severely limited by shoot regeneration rates, especially in commercial varieties. Although standardizing a transformation protocol is difficult due to genotype and season dependencies, use of an optimal mineral nutrient basal culture medium increases the success of recovering transgenic Citrus cells. The purpose of this study is to improve shoot regeneration from juvenile tissue in multiple Citrus genotypes. Explants of 11 Citrus cultivars were regenerated in 21 published media to determine the optimal media for each genotype. The number of shoots from juvenile tissue were counted 90 days after the explants were first cultured. The type of basal medium strongly affected the rates of shoot regeneration from Citrus juvenile tissue, and the effectiveness was negatively correlated with the level of ammonium. For each Citrus grouping, optimized media formulations were determined, and potential improvements were predicted. In general, medium R7100 appeared to be the most effective for regeneration of the Citrus genotypes tested.