Abstract:

A new Coix aquatica Roxb. cyto-type, found in the southwest of Guangxi Zhuang Autonomous Region in China, was identified and analyzed by acetocarmine squashing and fluorescence in situ hybridization (FISH) technique including genomic in situ hybridization (GISH). This new C. aquatica cyto-type was different from other C. aquatica cyto-types reported in chromosome structure. It was 2n = 30 in chromosome number, and ten bivalents plus ten univalents were formed in meiotic prophase and metaphaseⅠ. GISH results indicated that its 20 chromosomes were highly homologous to chromosomes of allotetraploid species C. lacryma-jobi L. (2n = 20). The 45S and 5S rDNA were respectively located on the two different chromosomes of the C. aquatica. One of chromosomes carrying 45S rDNA showed its chromosome shape and signal location in the C. aquatica as the same as that in C. lacryma-jobi. So did one of chromosomes carrying 5S rDNA. It could be deducted that one of parental candidates for the new C. aquatica cyto-type may be C. lacryma-jobi. The other parental candidate may be allooctopolyploid C. aquatica (2n = 40), which is similar to the new cyto-type of C. aquatica in aquatic habit and plant morphology.

Key words: Coix aquatica , rDNA, fluorescence in situ hybridization (FISH), genomic in situ hybridization (GISH)