MUTAGENESIS AND PLANT PHYLOGENESIS
V. G. Grif
V. L. Komarov Botanical Institute RAS, St. Petersburg
There are two types of genetic mutations-nuclear and cytoplasmic. We consider genic, chromosomic and
genomic nuclear mutations in several seed plant families characterized by different evolutionary age and life
forms. "Atlas of chromosome numbers of flowering plants" published in our laboratory in 1969 and containing
information about 35 000 species and periodical "Index to plant chromosome numbers" (USA) covering in all
about 150 000 species were used for comparative study of chromosome numbers. Gymnosperms originated
approximately 300 000 000 years ago and represented predominantly by arboreous and shrub forms are characterized
by practically total lack of polyploidy and rare aneuploidy, thus the evolutionary progress in this group has
been provided by genic mutations. The morphology of chromosomes in Gymnosperms is much more uniform as
compared with Angiosperms - all 200 species of Conifers have 24 large meta- and submetacentric chromosomes
Angiosperms. This group originated twice later includes 300 000 species with wide range of living forms-
from initial arboreous to ephemeric ones. Therefore, the dominating type of mutations for some groups of Angiosperms
as Fagaceae, Aceraceae, Aquifoliaceae, Caricaceae and Lauraceae is genic one. The major part of arboreous
Angiosperms has clear polyploid series like 2n = 28, 56, 84 (Betula) and 2n = 38, 76, 114 (Magnolia). Polyploidy
is the prevalent type of mutagenesis because of the advantage consisting in amplification of total number
of genes against a background of preservation of the genome integrity. The chromosomic type of mutations
prevalent in groups with asexual reproduction provides the flow of genes between genomes as a result of aneuploidy.
Genomic mutations are observed mostly in herbaceous plants. In such groups as Poaceae, Cyperaceae,
Ranunculaceae and Rosaceae we observe up to 90 % of polyploid species. Due to such ploidy restrictions like
the size of karyon, and the size and the number of chromosomes numerous shorter polyploid series are observed
in this group. Hence primitive mutations are prevalent in ancient Gymnosperms. Chromosomic and genomic
mutations arose later providing gene flow without functional changes of source genomes.
Key words: mutations, types of mutagenesis, polyploid series, chromosome numbers, phylogenesis
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