A protocol of homozygous haploid callus induction from endosperm of Taxus chinensis Rehd. var. mairei
Triploid nature of endosperm is the characteristic feature of angiosperms and is formed as a result of triple fusion. Present review discusses the morphogenic response and production of triploid plantlets by endosperm culture. Both mature and immature endosperm used for culture initiation responded differently in cultures. A key factor for the induction of cell divisions in mature endosperm cultures is the initial association of embryo but immature endosperms proliferate independent of embryo. In almost all the parasitic angiosperms, endosperm shows a tendency of direct differentiation of organs without prior callusing, whereas in autotrophic taxa the endosperm usually forms callus tissue followed by differentiation of shoot buds, roots or embryos. The endosperm tissue often shows a high degree of chromosomal variations and polyploidy. Mitotic irregularities, chromosome bridges and laggards are the other important characteristics of endosperm tissues. Triploids are usually seed sterile and is undesirable for plants where seeds are commercially useful. However, in cases where seedlessness is employed to improve the quality of fruits as in banana, apple, citrus, grapes, papaya etc. the induction of triploid plants would be of immense use. Triploid plants have more vigorous vegetative growth than their diploid counterparts. Hence, in plants where the vegetative parts are economically useful, triploids are of good use. This review focuses on the progress achieved so far in endosperm culture to obtain triploid plants.