Temperature-sensitive carrot variants impaired in somatic embryogenesis

Abstract

Cultured cells of many plant species are capable of regenerating back to plants. In carrots, plant regeneration takes place via embryogenesis. Because vast numbers of somatic embryos are produced from haploid carrot cultures, it is possible to design a selection procedure for recovering temperature-sensitive variants impaired in early embryogenesis ( ts-emb −). The ts-emb − lines fall into three classes. The first class is blocked before any growth in embryogenic medium can take place; the second class is blocked in organized growth: cells can grow as callus, but cannot form embryos; the third is blocked at the first stage of embryo development, the globular stage. These classes are useful in delineating the developmental steps during early somatic embryogenesis. The ts-emb − phenotype of most variant lines is stable in culture and is maintained through plant regeneration. Hypotheses are made concerning the origin of the ts-emb − phenotype. In addition to the ts-emb − lines, other classes of variants have been recovered, i.e., ts-growth −, habituated lines, and lines with altered responses to growth regulators.