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Meiotic consequences of selfing in grass pea (Lathyrus sativus L.) autotetraploids in the advanced generations: Cytogenetics of chromosomal rearrangement and detection of aneuploids
Published in -
Volume: 55
Issue: 2
Pages: 73 - 82
Meiotic consequences of an induced autotetraploid population were studied in advanced C4 and C5 selfing generations of grass pea (Lathyrus sativus L.). The tetraploids (2n = 4x = 28) segregated into progenies of normal tetraploid (NTT), tetraploid carrying reciprocal translocation (RTT), and aneuploids. Like its parent, NTT plants exhibited quadrivalent formation at meiosis I. The RTT plants, by contrast, consistently formed octavalent always in association with nucleolus at diakinesis, indicating involvement of nucleolar organizing chromosome in translocation at heterozygous condition. Both NTT and RTT plants showed higher bivalent formation than multivalent, although the latter manifested significantly better fertility and seed yield than NTT. Presumably, higher frequency of 8-shaped octavalent than ring configuration along with uniform occurrence of 10 bivalents ensured production of viable gametes in RTT plants. Among the aneuploids, pentasomy-trisomy (2n = 4x + 1 - 1 = 28) possessed a ring of nine chromosomes in RTT-derived progeny but an association of five chromosomes in NTT-selfed progeny. This suggested addition of translocated chromosome in the former case but quite normal one for the latter. However, the loss of one non-homologous chromosome in this aneuploid led the total chromosome number unaltered. Loss of one chromosome in tetrasome also led to formation of a primary trisomic (2n = 4x - 1 = 27), showing either 'Y' or frying pan-shaped trivalent. Two pentasomics, one single (2n = 4x + 1 = 29) and another double (2n = 4x + 1 + 1 = 30), showed formation of pentavalent/s regularly at metaphase I. The former two aneuploids showed higher fertility than pentasomics. The fitness of present autotetraploid has been discussed in the light of chromosomal rearrangement and regularization of meiotic process in grass pea. © 2012 Archana Sharma Foundation of Calcutta.
About the journal
JournalNucleus (India)