In vitro sexual and apomictic embryo sac development in Cenchrus ciliaris

Abstract

Sexual and aposporous apomictic embryo sac development in three Cenchrus ciliaris genotypes was evaluated in situ and in vitro. An aseptic procedure was developed to culture involucres in which the pistils contained archesporial cells. Development of sexual embryo sacs or differentiation and development of nucellar cells continued, in vitro, through mature embryo sac formation in the three buffelgrass lines. A numerical assessment system was devised to evaluate the stage of embryo sac development in vitro or in situ. Theculture medium contained Murashige and Skoog mineral salts supplemented with 1 × 10−4 M FeEDTA, 5.6 × 10−4 M myo-inositol, and 8.8 × 10−2 M sucrose in 1% agar. The best culture conditions were a 14 h light: 10 h dark photoperiod at a 25:19 °C (light:dark) temperature. Generally, 50% or more of the cultured involucres contained mature embryo sacs in good to excellent condition, and these sacs were indistinguishable from field-grown material. The in vitro culture technique provides a method to study embryo sac development and physiologic regulation of apomixis in Cenchrus ciliaris.