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Eleven plants were found to
have 15 bivalents (Table
2). The number of
univalents ranged between 0 to 7 per cell. Two plants, AD2 (4) 13 and
AD1 (4) 7 had thirty five chromosomes and formed 15 bivalents at
metaphase I in most of the cells. These plants thus had W from A and
B genomes and another bivalent from D genome. More interesting from
this point of view was the plant D (1) 4 with only four univalents
from D genome (2n = 34, 15" + 4'). AD1 (3) 7, another plant
with thirty four chromosomes and 15", had several multivalents (III =
0.24/cell, IV = 0.12/cell). Therefore, there are lesser chances of
obtaining a disomic addition plant in its progeny.
AD2 (11) 12 was found to be disomic addition plant (2n = 30,
15"). Efforts are presently underway to stabilize and identify the
added chromosomes.
Twenty nine plants had 14". The number of chromosomes ranged between
28 and 35 and number of univalents between 0 and 7. D(1) 1
(Fig.
1B), AD1 (8) 1,
AD2 (1) 2, AD2 (5) 6, AD2 (9) 1, AD2 (11) 9 and AD2 (12) 3 were
triple monosomic addition plants. AD1 (2) 6, AD1 (3) 4, AD1 (4) 3,
AD2 (1) 1b (Fig.
1C), AD2 (5) 8,
AD2 (7) 4 and, AD2 (11) 12 had thirty chromosomes each and all of
them were double monosomic addition plants. AD1 (1) 1, AD1 (1) 4 and
AD2 (6) 8 were monosomic addition plants (Fig.
1D). AD (1) 1 had
a high frequency of trivalents (0.48/cell). It is possible that the
added chromosome is involved in the trivalent, resulting due to
interchange heterozygosity or homoeologous pairing. The three
chromosomes involved in the trivalent are expected to segregate into
2:1 fashion. The chances of obtaining a disomic addition plant in its
progeny can thus be rated high since the extra chromosome will be
involved in a 2:1 segregation giving gametes with n = 15, 14
and thus reducing the chances of loss of extra chromosome by
elimination as laggard at anaphase I.
Acknowledgments
Financial assistance from SCS & T,U.P., is gratefully
acknowledged.
References
Gupta PK (1979) Utilization of alien genetic resources in wheat
improvement-achievements, possibilities and limitations. Ann Rev
Plant Sciences 1: 183-193.
Joppa LR (1973) Development of D-genome disomic substitution lines of
durum wheat (Triticum turgidum L). Proc IV Int Wheat Genet
Symp Missouri 1973 pp 685-690.
Joppa LR and McNeal FH (1972) Development of D-genome disomic
addition lines of durum wheats. Can J Genet Cytol 14: 335-340.
Joppa LR, Bietz JA and Williams ND (1979) The aneuploids of durum
wheats: D-genome additions and substitution lines. Proc V Int Wheat
Genet Symp New Delhi 1978 pp 420-426.
Yashvir and Kesavan PC (1979) Transmission and cytological behavior
of monosomic addition lines of D genome in Triticum durum
Desf. Proc V Int Wheat Genet Symp New Delhi 1978 pp 349-353.
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