Plant Molecular Biology 39: 1165–1173, 1999.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
Quantitative chromosome map of the polyploid Saccharum spontaneum by
multicolor ﬂuorescence in situ hybridization and imaging methods
, Paul H. Moore
, Don Heinz
, Seiji Kato
, Nobuko Ohmido
and Kiichi Fukui
Department of Genetics & Pathology, Hawaii Agriculture Research Center, 99-193 Aiea Heights Drive, Aiea, HI
Agricultural Research Service, U.S. Department of Agriculture, 99-193 Aiea Heights Drive, Aiea,
HI 96701, USA;
Division of Biotechnology, Yamanashi Prefecture Agricultural Experiment Station, Kitakoma
Laboratory Rice Genetic Engineering, Hokuriku National Agricultural Experiment Station,
Joetsu 943-0193, Japan;
Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita
565-0871, Osaka, Japan (
author for correspondence);
these authors contributed equally to this paper
Received 5 June 1998; accepted in revised form 23 November 1998
Key words: condensation pattern, image analysis, multi-color FISH of 45S and 5S rDNAs, polyploidy, quantitative
chromosome map, Saccharum spontaneum L., wild sugarcane
Somatic chromosomes of a wild relative of sugarcane (Saccharum spontaneum L.) anther culture-derived clone
(AP 85-361, 2n = 32) were identiﬁed and characterized by computer-aided imaging technology and molecular
cytological methods. The presence of four satellite chromosomes and four nearly identical chromosome sets
suggests that the clone is a tetrahaploid with the basic number x = 8. A quantitative chromosome map, or
idiogram, was developed using image analysis of the condensation pattern (CP) at the prometaphase stage of
somatic chromosomes. The 45S and 5S ribosomal RNA gene (rDNA) loci were simultaneously visualized by
multi-color ﬂuorescence in situ hybridization (McFISH) and precisely localized to the regions of 3p3.1 and 6q1.3
on the idiogram. The simultaneous visualization of two sets of four ribosomal RNA genes conﬁrms tetraploidy of
this clone. This conclusion is consistent with results of molecular marker mapping. The quantitative chromosome
map produced will become the foundation for genome analyses based on chromosome identity and structure.
Previously impossible identiﬁcation of small chromosomes and untestable hypotheses about the polyploid nature
of plants can now be settled with these two approaches of quantitative karyotyping and FISH.
Polyploidy is particularly prominent among an-
giospermplants.It is estimated that 30% to 35% of the
known species are polyploid . Almost 75% of the
species in Gramineae are polyploid . Polyploids
typically show a wider range of ecological tolerances
, and thus frequently occupy niches and habitats
that cannot be occupied by their diploid relatives.
The Gramineae, or grass family, is one of the
largest and most important families of ﬂowering
plants; according to Gould , it contains about 600
genera and 7500 species. This makes it the ﬁfth largest
family in number of species in the plant kingdom, but
tant. The Gramineae contains cereals such as wheat,
rice, maize, barley, grain sorghum, and pearl millet,
most of the forage and concentrated feeds consumed
by domestic animals, and the world’s most important
source of sucrose, sugarcane.
Sugarcane is a large grass of the genus Saccharum.
Polyploidy is recognized as extensive in Saccharum.
In fact, there is no known diploid form in this genus.
Although there is agreement about the polyploid state
of Saccharum, until recently neither the level nor
the type of polyploidy, i.e. either autopolyploidy or
allopolyploidy, was known. Aneuploidy is common
and is usually associated with hybridization between
ploidy levels. Understanding evolution in Saccha-
rum is complicated by natural hybridization across