The first record of tetrasomy in pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) |
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Authors: | Oleg E Kosterin Elvira R Galieva Vera S Bogdanova |
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Institution: | (1) Institute of Cytology & Genetics, Siberian Division of Russian Academy of Sciences, Acad. Lavrentyev ave. 10, 630090 Novosibirsk, Russia |
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Abstract: | Tetrasomic plants with two additional small chromosomes were identified, with a frequency about 2.5%, in the trisomic pea
line TRUST-R, which normally contains one extra chromosome covering a sporophyte lethal in the regular chromosome set. As
compared to trisomics, tetrasomics exhibited an enhanced expression of the traits resulting from extra chromosome addition:
slow growth, enlarged bracts, shortened peduncles, wavy leaflets and stipulae. They were almost sterile, their pollen contained
a variable proportion of empty grains and some anomalously large, small or deformed grains. In metaphase I, two extra chromosomes
did not form a stable bivalent and only in some cases were situated close to each other. In anaphase I, the extra chromosomes
migrated independently to either pole or retarded in the equatorial plain, the same was observed for chromatids in anaphase
II. This retardation resulted in anomalous cytokinesis, so that triads, dyads and half-divided or non-divided monads appeared.
The retarded extra chromosomes may form small extra nuclei either included into one of the microspores or forming a separate
miniature cell; in this way tetrasomics may eliminate extra chromosomes. One of the tetrasomics analysed formed an exceptionally
high proportion of microspore pentads. In the regluar TRUST-R trisomics, the sole extra chromosome retarded in the equatorial
plain in anaphases I and II. The retardation in anaphase II often makes cytokinesis in trisomics (in general more regular
than in tetrasomic) to proceed in two steps: at first cell wall formation separates a pollen mother cell into two dyads and
then each of them into two microspores. |
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Keywords: | Tetrasomics Minichromosome Extra chromosome Meiosis anomalies Garden pea Pisum sativum L |
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