Haploid Induction via In vitro Gynogenesis in Tomato (Solanum lycopersicum L.)

In order to determine the potential for haploid induction via in vitro gynogenesis in tomato, the ovules and protoplasts of embryo sacs from the hybrids Zhongza 101 and Zhongza 105 were cultured. An efficient method of ovule isolation was established in this study. Using this method, 100-150 ovules could be isolated from one ovary. Isolated ovules were cultured on three induction media to induce gynogenesis in vitro. During culture, ovules were enlarged markedly, with opaque white color. When observed microscopically, there were cell divisions and cell clumps in embryo sacs. Subsequently, the cell clumps in embryo sacs ceased growth, likely because the integument grew faster than embryo sacs did and hindered the further development of embryo sacs. Therefore, subsequent callus morphogenesis might be originated from the integument. Thousands of calli from the two tomato varieties were obtained. Five diploid plants were regenerated after 15 months of subculturing. To eliminate the hindering effect of integument on embryo sac cells, the protoplasts of embryo sacs were prepared and cultured. After 48 hours of culture, the protoplasts of embryo sacs doubled in size and gradually formed clusters of cells. These results suggested that gynogenesis might be a potential way for haploid induction in tomato.