Somatic embryogenesis and regeneration of Kenyan wheat (Triticum aestivum L.) genotypes from mature embryo explants

Abstract

Wheat (Triticum aestivum L.) improvement via genetic transformation depends on an efficient regeneration system for recovery of transgenic events. This study reports a somatic embryogenesis-based regeneration system for two Kenyan wheat genotypes (Eagle 10 and Njoro bread wheat II) from mature embryos. The study investigated the efficiency of mercuric chloride, commercial bleach, and chlorine gas in surface sterilizing explants prior to in vitro culture. Callus induction and somatic embryogenesis were done by culturing wheat mature embryos in Murashige and Skoog (MS) medium supplemented with 2, 4-dichlorophenoxyacetic acid (2,4-D) used either singly or in combination with 1-naphthaleneacetic acid (NAA), 4-chlorophenoxyacetic acid (4-CPA) or 6-benzylaminopurine (BAP).  Embryo germination and plantlet recovery were done by culturing embryogenic callus in MS medium without plant growth regulators (PGRs). Chlorine gas was significantly (p<0.001) the most effective in surface sterilization and maintenance of explant viability. All 2, 4-D concentrations tested (1, 2, 4 and 8 mg/l) induced embryogenic callus. A significantly higher callus induction rate and callus fresh weight were obtained when 2,4-D was used in combination with either NAA or 4-CPA than when it was used singly.  Combining 2,4-D with BAP led to a significantly lower callus induction frequency. Somatic embryo germination was achieved in MS medium without plant growth regulators. These findings have the potential to inform future efforts in the application of modern biotechnology for accelerated wheat cultivar improvement.     Key words: Wheat, somatic embryogenesis, mature embryos.