Synaptic variation derived plausible cytogenetical basis of rarity and endangeredness of endemic Mantisia spathulata Schult

Abstract

We studied meiosis in Mantisia spathulata, a rare, endangered and endemic rhizomatous horticultural herb showing synaptic variation. Most of pollen mother cells (PMCs) analyzed at either diplotene or diakinesis/metaphase I did not exhibit the expected chromosome associations of 10II, which is indicative of synaptic variation. Seventeen percent of the PMCs have shown normal meiotic pattern while 83% PMCs were with abnormal meiotic behavior of bivalents. A total of 419 bivalents and 1,162 of univalents were recorded with significantly low chiasma frequency (8.38 ± 6.20) and terminalization coefficient of 0.82 only. We recorded in 53.33% PMCs, an anomalous distribution pattern of chromosomes, including unequal distribution and/or presence of laggards in the form of univalents/bivalents resulting in low pollen stainability. We suggest that the imbalanced meiosis with variant synaptic behavior of bivalents recorded in M. spathulata may be responsible for loss of genetic variation and considered as substantial cytogenetical factors leading to the rarity and endangeredness of the species.