Organogenesis from Immature Pecan Embryonic Axes in Vitro

Abstract

Immature embryos were excised during kernel development from fruits of the pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars Desirable and Stuart. The cotyledons were removed and the main embryo axes were used as explants. Explants were cultured in vitro on media containing various levels of cytokinins and auxins. Morphogenesis in ‘Stuart’ preceded that of ‘Desirable’ by 1 to 2 weeks. In both cultivars, the percentage of embryo axes forming shoots only or both shoots and roots increased until ≈4 to 6 weeks before nut maturity, as judged by shuck dehiscence. After this time, developmental responses declined. Production of normal plants was highest on a medium containing IBA, BA, and kinetin at 0.5, 4.4, and 9.3 μM, respectively. Shoots only were obtained on a medium containing cytokinin without auxin and roots only on a medium containing auxin with no cytokinin. Axillary shoots elongated from embryo axes of both cultivars. This response was greatest on a medium containing cytokinin as the only hormone for ‘Desirable’, but with both auxin and cytokinin for ‘Stuart’. Chemical names: indole-3-butyric acid (IBA); N-(phenylmethyl)-1H purin-6-amine (BA); N-(2-furanylmethyl)-1H-purin-6-amine (kinetin).