Highly Unstable Male Meiosis in Two Aberrant Plants Isolated from the Mutant Population of Nigella damascena L. (love-in-a-mist)

Abstract

Two aberrant (plant type I and II) plants possessing meiotic instability in the microsporocytes were identified from the mutant population of Nigella damascena L. (commonly known as love-in-a-mist; family: Ranunculaceae). Plant type I (screened from 10 kR M₁ generation) was a weak plant with small sized flowers and shrunken anthers devoid of any pollen grains at anthesis. The plant dried up at blooming stage. Male meiotic study revealed the occurrence of condensed and compact chromatin masses of variable sizes and numbers (12 to 13 mostly and 3 to 5 rarely) and occasional formation of bivalent and univalent like configurations in the meiocytes. Plant type II (isolated at M₂ from the M₁ progeny of 0.25% EMS treatment) was a small flower mutant (SF2), the morphological nature and chromosomal behaviour of which have been compared to control and SF1 (small flower mutant arising in different M₂ line). SF1 showed similar morphological behaviour as SF2 but demonstrated normal meiosis like control. SF2 manifested hypoploid (2n<12), diploid (2n=12) and hyperploid (2n>12) chromosome numbers at MI and AI and prevalence of unstable meiosis in the form of asynaptic and desynaptic chromosome behaviour, differential condensation of chromosomes, persistent nucleolar body and occasional multivalent formation in first and mid-flowering phases. SF2 showed more diploid PMCs at late flowering phase. SF2 was also found to be associated with defects in female gametophytic tissues. Possible mode of gene action in the plant types has been predicted.