CYTOLOGICAL STUDIES IN SOME WILD TUBER-BEARING SOLANUM
CYTOLOGICAL STUDIES IN SOME WILD TUBER-BEARING SOLANUM
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Date
1983-06
Authors
SANGOWAWA, BENJAMIN GBEKELEOLUWA
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Abstract
Cytological studies were carried out in eight
tuber-bearing wild Solanum species namely,
1. S. mochicense Ochoa, 2. S. boliviense Dun.,
3. S. raphanifolium Card et Hawkes, 4. S. pinnatisectum
Dun., 5- S. stenotomum Juz. et Buk., 6. S. chacoense
Bitt., 7. S. kuntzianum Bitt. et Wittm. and 8. S.
polytrichon Rydb. The haploid number in six species
(1-6) is found to be 12 (n= 12) and they are therefore
diploids and the two species namely, S. kuntzianum Bitt.
et Wittm and S. polytrichon Rydb. are found to have 24.
haploid number of chromosomes (n= 24.) and are therefore,
tetraploids.
Detailed meiotic studies have been made of the
diploid and tetraploid species, and frequency of
chiasmata in each species has been analysed both in
diplotene and diakinesis and the terminalisation values
of each of them have been estimated.
Association of chromosomes in three or four or more
are seen in diploid species. The frequency of multivalents
have been analysed. The occurrence of multivalents in
diploids indicate the presence of translocation
heterozygotes. In tetraploids the percentage of
quadrivalents varies from 47.58 to 57.42 in
S. kuntzianum and S. polytrichon respectively, and this
high degree of association of four chromosomes to form
quadrivalents seem to indicate that these two species
are autotetraploid in origin.
The incidence of pairing of homologues in diploids
and tetraploids have been analysed and the frequency of
failure of pairing have also been estimated.
The univalents which are formed due to failure of
pairing among pairable chromosome mates behave in
different ways in diploids and tetraploids. They either
pass to the poles or lag between separating group of
chromosomes or divide. The division and elimination of
univalent causes unequal distribution of chromosomes in
second metaphase and the frequency of these unequal
distribution of chromosomes in diploids and tetraploids
were analysed and the effects of these aberrations in the
formation of morphologically good and deformed pollen
have been studied.
The formation of dicentric chromosomes involving
chromatid bridges and fragments is found to be a usual
phenomenon in the diploids and tetraploid species and their
significance on sterility has been analysed and discussed.
The secondary association of chromosomes occur in all
species under consideration. There is preponderance of
association of two over other groups of chromosomes in
diploids and the significance of four groups of 2 and
four free chromosomes has been discussed.
The cytological behaviour of chromosomes in
diploid Solarium under consideration indicates that
there is a good evidence of regarding them as of
hybrid origin. It is also apparent that the main
lines of evolution in Solarium species investigated
is that of interspecific hybridization and occurrence
of polyploidy.
Description
A thesis submitted to the Postgraduate School,
Ahmadu Bello University, in fulfilment of the
requirements for the degree of DOCTOR OF PHILOSOPHY
(with sixty eight tables and sixteen plates)
Department of Biological Sciences,
Faculty of Science,
Ahmadu Bello University, Zaria.
JUNE, 1983
Keywords
CYTOLOGICAL,, SOME WILD,, TUBER-BEARING,, SOLANUM