Cytogenetic investigation of some Euphorbiaceae in Thailand

Abstract

Cytogenetic investigations of 36 species, 18 genera, Euphorbiaceae in Thailand were discussed for the first time. The techniques of propionocarmine smear and Feulgen squash has been developed for obtaining meiotic and mitotic chromosomes. The results revealed that there are the great diversity of chromosome numbers between and within the genera from 2n= 16 to 104. Most species have very small chromosomes ranging from 1.0 to 3.33 μm. Strophioblachia fimbricalyx Boerl. is a distinct species which have the largest chromosomes with the length of bivalents about 5.33-8.67 μm. It was found polyploids in both natural groups and cultivated plants. Croton spp. (2n=20, x = 10) and Jatropha spp. (2n=22, x = 11) showed the uniform chromosome number within the genus. The chromosomes of Euphorbia studied are very variable in sizes and numbers ranging from 2n= 16 to 60. New chromosome numbers for 16 species involving 12 genera are reported for the first time. Phyllanthus emblica L. has 2n= 104. It is varied from the previous recorded (2n=28, 98 and 104). B chromosomes were found in P. pulcher Wall. ex Muell. Arg. uniquely. This preliminary study indicates that chromosome number, chromosome size and certain morphological differences may suggest that the Euphorbia could be broken up into several genera.