A filter paper-based liquid culture system for citrus shoot organogenesis—a mixture-amount plant growth regulator experiment

Abstract

This study determined the effects of a static liquid culture system on shoot regeneration from citrus epicotyl explants. A mixture-amount experiment was used to determine the effects of zeatin riboside (ZR), 6-benzylaminopurine (BA), and indole-3-acetic acid (IAA) on two citrus types—citrange (Citrus sinensis ‘Washington’ L. Osbeck. × Poncirus trifoliata L. Raf var. Carrizo) and sweet orange (Citrus sinensis L. Osbeck var. ‘Ridge Pineapple’). A liquid culture system comprising a Petri dish, cellulose filter paper, and liquid culture medium was used. Shoot regeneration experiments were conducted over 6 wk that included 2 wk in the dark followed by 4 wk in the light. Three responses were measured: (1) number of explants forming buds and/or shoots, (2) number of explants with shoots > 2 mm, and (3) overall explant and shoot quality. The effects of paper disc number, liquid medium volume, and explant size on shoot regeneration were determined. High-quality shoots were produced from explants cultured in 5.25 to 12 mL medium volume and explant sizes ranging from 2 to 15 mm. The effects of the plant growth regulators were similar for the two citrus types and were as follows: (1) use of ZR or BA resulted in high-quality shoot production; (2) ZR and BA were not synergistic; (3) culture in 20 μM ZR resulted in the highest shoot production; (4) BA and IAA were strongly synergistic, with the greatest production with BA when IAA was included in the mixture; and (5) ZR and IAA were antagonistic, particularly with Ridge Pineapple.