Cytological status of Allium hookeri Thwaites (2n = 22)

Determining the base number, ploidy level and type of ploidy are important aspects in the cytogenetic study of a species. To assess the nature of Allium hookeri Thwaites (2n=22), chromosomes of its two populations from North-eastern Himalayas were worked out for morphological details, putative group...

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Bibliographic Details
Published in:Genetic resources and crop evolution 2011-10, Vol.58 (7), p.1041-1050
Main Authors: Sharma, Geeta, Gohil, R. N., Kaul, Veenu
Format: Article
Language:English
Subjects:
Agriculture
Allium
Allium hookeri
Anomalies
Biomedical and Life Sciences
Chromosomes
Cytogenetics
Genomes
Heterozygosity
High frequencies
Homology
Life Sciences
Meiosis
Metaphase
Morphology
Plant Genetics and Genomics
Plant Physiology
Plant Sciences
Plant Systematics/Taxonomy/Biogeography
Ploidy
Pollen
Polyploidy
Reduction
Research Article
Sterility
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Summary:Determining the base number, ploidy level and type of ploidy are important aspects in the cytogenetic study of a species. To assess the nature of Allium hookeri Thwaites (2n=22), chromosomes of its two populations from North-eastern Himalayas were worked out for morphological details, putative grouping and pairing properties during reduction division. Karyotype was found to split into 7 pairs and 8 single chromosomes; 7 pairs revealed minor differences in overall chromosome morphology. Critical analysis of chromosome behaviour during reduction division at diakinesis and metaphase I revealed the presence of trivalents in 60.5 and 58.5% pollen mother cells respectively. High frequency of cells with trivalents pointed towards considerable homology in three genomes. Though remaining cells had multivalents higher than trivalents, similarity in three genomes was there. High frequency of cells with trivalents and the fact that 22 chromosomes can be arranged in seven twos and eight ones indicated that these represent numerical variants of segmental allotriploids. Besides, occurrence of 29.8 and 17.6% chromosomes as multivalents higher than trivalents at diakinesis and metaphase I supported that multiple interchanges accompanied the polyploidy in the evolution of present cytotypes. Pairing anomalies noticed during meiosis result in very low pollen stainability (0.05%) leading to sterility. Propagation by bulbs ensures the survival and maintenance of such a complex heterozygosity in the species.
ISSN:0925-9864
1573-5109
DOI:10.1007/s10722-010-9641-x