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Abstract
Male meiotic studies in eight Indian Cucumis species, including two newly included species, have been carried out. Gametic chromosome numbers of n = 7 and 12 were recorded in these taxa. Data collected on chromosome associations, chiasma frequency at diplotene/diakinesis/metaphase I revealed the predominant occurrence of bivalents in the majority of the pollen mother cells (PMCs) of taxa having n = 7, suggesting a high degree of homology among the pairing chromosomes. Conversely, species with n = 12 had chromosome associations resulting in a mixed of bivalents and univalents. One of the reasons for such heterogeneity exclusively found in these species may be attributed to chromosome structural alteration at DNA level (duplication/deletion/point mutation) rather than numerical alteration. Multivalents were not encountered in any of the PMCs, indicating the diploid nature of the taxa. A single nucleolus showing affinity towards varying numbers of bivalents (1–4) was the hallmark feature of the PMCs analyzed at diplotene.
Acknowledgment
The present work is supported by a World Bank funded consortium research project of ICAR, New Delhi through the NAIP program. Sincere thanks are due to Prof. M.S. Bhist, Centre for Science Education, NEHU and Mr. Santosh Kumar Sharma and all other members of Plant Biotechnology Laboratories, Department of Botany as well as Department of Biotechnology & Bioinformatics, NEHU, Shillong for their constant encouragement and help.