Cytological studies in the family Zingiberaceae with special reference to chromosome number and cyto-taxonomy

Abstract

Somatic chromosome numbers have been determined mostly for the first time for 24 species, spread over 7 genera. Chromosome complements in Zingiber officinale, Z. zerumbet, Z. cassumunar, Costus igneus and C. discolor have been analysed. The basic numbers 6, 9, 11, 12, 13 and 21 are suggested for the genera Kœmpferia, Costus, Zingiber, Alpinia, Hedychium, Elettaria, Globba and Phœomeria. 6 appears to be the primary basic number, the others representing secondary balances of this primary number. A biphyletic origin is suggested for the species of Hedychium one from the basic number 9 and the other from the basic number 13. Speciation in this family has been found to be due to polyploidy, aneuploidy and structural changes. The 42 chromosomed members of the genus Curcuma are believed to be arnphidiploids derived from a cross between 12- and 9-chromosomed ancestors. It is also suggested that Curcuma longa is likely to be a triploid form of C. aromatica. The distinctive nature of the chromosomes of Costus, their morphology and number, would appear to justify the separation of this genus into a tribe or sub-order.