Abstract
The Buffelgrass (Cenchrus ciliaris L., Poaceae) is one of the most important pasturage grasses due to its high productivity and good forage qualities. This species possess a high adaptability to bioclimatic constraints of arid zones and may be used for the restoration of degraded arid ecosystems. Tunisian populations present three ploidy levels (4x, 5x and 6x) with a basic chromosome number x=9. This study reported for the first time the distribution of the ribosomal genes (rRNA) for pentaploid and hexaploid cytotypes of Cenchrus ciliaris. Molecular cytogenetic study using double fluorescence in situ hybridization has shown that the two rDNA families, 5S and 18S-5.8S-26S (18S), displayed intraspecific variation in number of loci among different ploidy levels. Each ploidy level was characterized by specific number of both 5S and 18S rDNA loci (two loci in tetraploid, five in pentaploid and six in hexaploid level). For three studied cytotypes (4x, 5x and 6x) all 5S rDNA loci were localized on the subcentromeric region of chromosomes, while 18S loci were situated on the telomeric region of short chromosome arms. Data of the FISH experiments show proportional increase of ribosomal loci number during polyploidization processes.
Highlights
In the south of Tunisia, the ecosystems are characterized by a high level of anthropogenic disturbance and have been characterized by several factors such as climatic variations and overgrazing (Le Houérou and Hoste 1977)
This study reported for the first time the distribution of the ribosomal genes for pentaploid and hexaploid cytotypes of C. ciliaris
It was observed that number of 5S and 18S ribosomal DNA (rDNA) loci increased, as expected, with ploidy level (Fig. 2): tetraploid individuals possessed four, pentaploids five, and hexaploids six loci
Summary
In the south of Tunisia, the ecosystems are characterized by a high level of anthropogenic disturbance and have been characterized by several factors such as climatic variations and overgrazing (Le Houérou and Hoste 1977) These ecosystems are subjected to high aridity, decrease of biological productivity (Floret et al 1981), where the perennial species are most affected (Jauffret and Lavorel 2003). Cenchrus ciliaris is especially important in the semi-arid regions because of its high tolerance and adaptability to hot and dry environments (Hall 2001), and its resistance to cutting (Chaieb et al 1996) This species is highly polymorphic and variable for several morphological traits of ecological and agronomic importance (Mseddi et al 2004). The embryological and karyological studies of C. ciliaris have shown the aposporous mode of reproduction followed by pseudogamy (Ozias-Akins et al 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
