Meiotic Irregularities in Tetraploid Aloe arborescens Miller and Their Consequences
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Meiotic Irregularities in Tetraploid Aloe arborescens Miller and Their Consequences Mehnaz Bano1 • Geeta Sharma1
Received: 20 December 2017 / Revised: 9 July 2018 / Accepted: 9 January 2020 The National Academy of Sciences, India 2020
Abstract Aloe arborescens, cultivated in India for its ornamental and medicinal value, commonly exists as diploid (2n = 2x = 14) and rarely as tetraploid (2n = 4x = 28). A single previous report on meiosis in the tetraploid form indicated the presence of univalents to quadrivalents at metaphase I, with no information on later meiotic phases and post-meiotic consequences of pairing anomalies. To fill these crevices, a cytologically unstudied population from Jammu (India) was investigated for chromosome associations, chromosome constitution of microspores and seed set. Analysis of pollen mother cells (PMCs) at diplotene/metaphase I revealed the presence of bivalents to quadrivalents in 38% cells, with remaining having 14 bivalents. Besides, anomalies in the form of bridges and/fragments were apparent in 70.9% and 66.6% PMCs at anaphases I and II and in 44.4% and 25% cells at telophases I and II. Screening of dividing microspores of individual anthers revealed interspersing of normal reduced microspores (n = 2x = 14) with unreduced (2n = 4x = 25–26) and hypoploid reduced (n = 2x - 3 = 11) ones, with their frequency of occurrence being 50%, 30% and 20%, respectively. Though the plants of this species flower (67 ± 7.4 per inflorescence) profusely, few flowers (7.88 ± 0.83 per inflorescence) mature into fruits and fewer seeds (7.83 ± 0.91 per fruit) are set. The reduced seed set in the present cytotype seems to have
& Mehnaz Bano [email protected] Geeta Sharma [email protected] 1
Department of Botany, University of Jammu, Jammu, Jammu and Kashmir, India
resulted from meiotic anomalies prevalent and existence of aneuploid and unreduced microspores. Keywords Aloe arborescens Miller Aneuploid Tetraploid Multivalent Pollen mitosis
Aloe arborescens Miller, a winter-blooming succulent with bright orange flowers and attractive foliage, is of great ornamental and medicinal value. Its leaf extracts, containing antimicrobial, antifungal and antioxidative components, are used as dietary supplement and for treating wounds, constipation, ulcer and cancer [1, 2]. Despite importance, A. arborescens has been scarcely studied for cytological aspects. Studies by the previous workers [3–8] revealed its existence in diploid form except Vij et al. [9] who noted a tetraploid cytotype from Chandigarh (India), with its chromosomes occurring as univalents to quadrivalents at metaphase I. Data on frequency of chromosomes forming varying associations, later meiotic aspects and post-meiotic consequences of multivalent formation, however, lacked for the tetraploid cytotype. To scaffold these crevices and to understand relationship between chromosome behavior and fertility of tetraploid A. arborescens, a cytologically unstudied population from Jammu was studied for chromosome
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