Studies on the Cytology and Phylogeny of South Indian Grasses

I. Subfamilies Bambusoideae, Oryzoideae, Arundinoideae and Festucoideae

Abstract

Cytological studies have been made of South Indian grasses with a view to re-examine the taxonomic status and inter-relationships of the various tribes and genera making use of the additional evidence from cytology. The present paper deals with the cytology of 24 species representing 16 genera. Of these, the cytology of 14 species has been studied for the first time.
The chromosomes of most of the species are very small, ranging in length between 1μ and 2.5μ. As reported by previous workers, the basic chromosome number of the grasses ranges from 5 to 12. Chromosome number in multiples of 8 which has been reported to be a rare occurrence in the grass family has been encountered in two species, viz. Arundinella setosa (n=8) and A. mesophylla (2n=16).
The presence of high polyploid and aneuploid chromosome numbers shows the role of polyploidy in the evolution of the bamboos. The Bambuseae, Oryzeae and the Arundineae are closely related as they have high polyploid numbers in multiples of 12. The Aristideae is a highly advanced tribe, probably derived from the Arundineae. The Centotheceae is closely related to the Oryzeae as suggested by de Wet (1960). The present cytological evidence shows that Thysanolaena is related to the Arundineae.
The present study has confirmed the systematic position assigned to the Arundinelleae by Stebbins and Crampton (1961). The Festuceae and the Aveneae which are closely related morphologically, have large chromosomes with the dominant basic number 7.