Abstract
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.
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Acknowledgments
The authors are grateful to the Head, Department of Botany, University of Jammu, Jammu for providing the necessary facilities and National Bureau of Plant Genetic Resources (Bhowali) for providing the plant material. Council of Scientific and Industrial Research, Govt. of India, New Delhi is also gratefully acknowledged for providing financial assistance to the first author.
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Sharma, G., Gohil, R.N. & Kaul, V. Cytological status of Allium hookeri Thwaites (2n = 22). Genet Resour Crop Evol 58, 1041–1050 (2011). https://doi.org/10.1007/s10722-010-9641-x
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DOI: https://doi.org/10.1007/s10722-010-9641-x