Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 57pg1
MATERNAL PHYLOGENY WITHIN THE 'Saccharum COMPLEX'
Salah M. Al-Janabi 1, Danielia Braga 2, Eric LaHood 2, Paul Kelm
2, and Bruno W.S. Sobral 1. 1 California Institute of Biological
Research. 11099 North Torrey Pines Road, Suite 300, La Jolla, CA
92037; 2 Northern Arizona University, Department of Biology,
Flagstaff, AZ 86011.
The chloroplast genome of Saccharum officinarum 'Black
Cheribon' was physically mapped. A set of 13 probes that cover
the entire rice chloroplast genome was used in combination with
21 restriction enzymes to determine the level of variability
present in the chloroplast of Saccharum and related genera (33
genotypes, representing 8 genera and 9 species). Direct DNA
sequencing of the intergenic region between rbcL and atpB,
between the chloroplast tRNAval and the 16S rRNA, and between the
mitochondrial 18S and 5S genes was also done on a larger set of
genotypes. Six of the genera studied: Saccharum, Miscanthus,
Erianthus, Narenga, Eccoilopus and Sclerostachya, are part of the
Saccharinae subtribe, whereas the other three; Oryza, Zea, and
Sorghum were used as outgroups. RFLP analysis of chloroplast DNA
yielded 69 independent restriction site mutations, of which
nearly 40 were phylogenetically informative. Phylogenetic
analyses by cladistic parsimony and maximum likelihood were used
to generate phylogenetic hypotheses. Restriction site mutation
divided the 33 genotypes into 10 different chloroplast groups
(cytotypes); 7 from within the Saccharinae and the outgroup
species. Phylogenetic hypotheses obtained using both approaches
were congruent. These trees clearly showed that the maternal
lineages of Narenga, Miscanthus, Sclerostachya, and Saccharum
formed a monophyletic group. However, 5 of 6 Erianthus species
and the one Eccoilopus species clearly were not part of that
group and were much more related to Sorghum bicolor. One
Miscanthus sp. from New Guinea that has a very high chromosome
number (2n=192) was shown to have the same cytotype as the
majority of the members of the Saccharum genus, suggesting that
interspecific hybridization between these genera can occur in the
wild. The Saccharum genus could be broken into two clades: one
containing S. spontaneum and the other containing all remaining
Saccharum species and all 8 commercial hybrids (from various
growing countries). This means that all high-sucrose producing
Saccharum genotypes and all commercial sugarcane varieties
currently in use most likely contain only one cytotype.
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