Diphenylurea derivatives induce somatic embryogenesis in Citrus

The present research investigates the possibility that three diphenylurea (DPU) derivatives, N-phenyl-N'-benzothiazol-6-ylurea (PBU), N,N'-bis-(2,3-methilendioxyphenyl)urea (2,3-MDPU) and N,N'-bis-(3,4-methilendioxyphenyl)urea (3,4-MDPU), stimulate the induction of somatic embryogenesis in three Citrus species. The hypothetical embryogenic activity was assessed using stigma and styles of Citrus myrtifolia Raf., Citrus madurensis Lour. and Citrus limon (L.) Burm. The three compounds influenced the production of somatic embryos differently as regards the concentrations tested and the citrus species. PBU was able to induce somatic embryogenesis at all the concentrations tested and in all the three species with percentages that ranged from 44 (C. limon) to 85% (C. myrtifolia). 2,3-MDPU and 3,4-MDPU were completely unable to induce the production of somatic embryos in C. myrtifolia while both the compounds at the higher concentration (12 mu M) acted positively in both C. madurensis and C. limon (68% of embryogenic explants). The phenylurea derivatives, used for the first time in this study to induce somatic embryogenesis in plant, showed a higher embriogenic performance when compared with 6-benzylaminopurine (BAP), a classical adenine-cytokinin, and with N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU), a classical DPU derivative.