Karyomorphological and Phylogenetic studies on Hygroryza aristata (Retz.) nees of the tribe Oryzeae.

Abstract

Detailed cytological analysis including karyomorphology, meiosis and pachytene studies have been carried out for the first time in Hygroryza aristata, a monotypic genus belonging to the tribe Oryzeae. Incidentally this is also the first report on pachytene studies of another genus of this tribe, as all previous pachytene studies have been confined to a few species of Oryza only. Meiosis showed secondary association of bivalents, association in a 3-5 groups of two bivalents each were commonly observed. Pachytene chromosomes were of the differentiated type, the unstained centromeres were flanked by proximal dark-staining heterochromatic regions and distal light staining euchromatic regions. There is complete pairing between all homologous chromosomes. Two bivalents were found constantly associated with the nucleolus at pachytene and diakinesis and four chromosomes with secondary constrictions were observed at somatic metaphase. The pachytene analysis clearly demonstrates that chromosomes VI and VIII and also XI and XII are morphologically similar and appear as duplicated types. The body of evidence clearly indicates that the monotypic Hygroryza and Oryza, which are grouped togehter on the basis of morphological characters show close resemblance in their cytological behaviour also.