Maturation of avocado somatic embryos and plant recovery

Abstract

Avocado proembryonic masses from suspension cultures were used to develop a protocol for somatic embryo development and maturation. Avocado somatic embryos could develop from proembryonic masses both in liquid and on semisolid medium but only the latter could develop to maturity. Size and number of opaque somatic embryos were affected by gellan gum concentration, with the optimum response obtained on medium supplemented with 6–7 g l−1 gellan gum. The optimum sucrose concentration for recovery of opaque somatic embryos was 90 g l−1; however, the development of embryos was suppressed at this concentration. Consequently, recovery of cotyledonary, opaque somatic embryos was achieved on medium with 30 g l−1 sucrose. Somatic embryo development from dedifferentiating proembryonic masses required media with a high ratio of NO3−:NH4+ (1:0 and 3:1) as opposed to the standard ratio (2:1) of MS medium. Germination of somatic embryos was sporadic. In order to increase the frequency of plant recovery, shoots that developed from somatic embryos were micropropagated using standard protocols.