Plant regeneration from undeveloped ovules and embryogenic calli of Citrus: Embryo production, germination, and plant survival

Abstract

Embryogenic cultures were initiated from undeveloped ovules of several polyembryonic Citrus species on a basal medium supplemented with either malt extract, 2,4-D alone, or 2,4-D in combination with BA or daminozide. Primary embryos of all responsive cultivars were harvested directly from ovule cultures; secondary embryo harvests were made from ‘Handin’ orange ovule cultures and long-term embryogenic callus. Differences were observed among cultivars and treatments in percentage of responsive ovules and total number of embryos produced. The most effective treatment for embryo production varied among cultivars. Embryo germination and plant establishment frequencies were determined for this plant regeneration system. Differences among cultivars with respect to regenerate survival percentage were minimal. Plant regeneration via secondary or long-term callus-derived embryos was as efficient as from primary embryos. Critical factors influencing plant production and survival were the production of normal viable embryos, balanced germination, and successful acclimatization to the external environment.