A cytological study on early development of endosperm in maize (Zea mays L.)

Abstract

The importance of maize (Zea mays L.) endosperm can not be overemphasized as it constitutes the bulk of economic yield of this crop and provides nutritive support to the developing embryo. Endosperm originates from the double fertilization phenomenon where the two haploid polar nuclei of the embryo sac get fertilized by one of the sperms to produce the triploid initial material [1]. The transfer of apomixis gene(s) from wild species into cultivated crop plants may open up the possibilities for preservation of hybrid vigor over generation [2]. However, inter-ploidy crosses in maize invariably lead to failure of endosperm development and seed abortion [3, 4]. Also, not much is known about endosperm development and the role of varying endosperm ploidy levels on normal endosperm development. In case the apomixis trait is introduced into maize, the endosperm ploidy levels would be diploid, triploid, tetraploid, pentaploid depending on whether the embryo sac is monosporic, bisporic or tetrasporic and whether the endosperm development is pseudogamous or autonomous. Precise knowledge about the endosperm development and its cytogenetic basis is important for successful transfer of apomictic gene(s). The present study was undertaken to analysed the initial stages of endosperm development in diploid, tetraploid and interploidy crosses, like 2n x 4n, 4n x 2n, 3n x 2n and (2n + 1) x 2n to get an insight into the role of varying ploidy levels on endosperm development in maize. The materials used in this study included two diploid inbred lines (CM 105 and CM111), one tetraploid (derivative of Alexanders Synthetic B tetraploid), two sets of triploids (obtained by crossing the tetraploid stock by two diploid inbred lines, CM105, CM111) and one trisomic stock (primary trisomy for chromosome 10).