Cytogenetic studies of some Kenyan tea clones (camellia Sinensis) l.o. kuntze) karyotype and ploidy.
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Date
1990
Authors
Wachira, Francis Nyamu
Journal Title
Journal ISSN
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Publisher
Kenyatta University
Abstract
A comparative intraclonal analysis of ploidy states
and karyotypes was performed on eight Kenyan tea clones
(Camellia sinensis L.O. Kuntze), by examining shoot
meristematic cells. C-metaphase chromosomes were studied
by acetopropionic orcein staining methods. Several
karyotypic variables VJere determined for each clone;
chromosome number, short arm length (S), long arm length
(L), total chromosome length (TL), arm ratio (r), relative
chromosome 1ength (RL), and the presence or absence of
secondary constrictions and satell ites (SAT). Clones 7/9,
S15/10, 6/8, 31/8, TN14/3 amd 57/15 were all shown to be
diploids w it.h chromosome complements of 2n - 2x = 30.
Clones 84/2 and 84/1 we re confirmed to be naturally
occurring triploids with chromosome complements of
2n=3x=45.
Analysis of variances for the means of chromosomal
variables, notably total chromosome lengths, indicated
that there were significant (P<0.05) differences between
chromosome pairs within each complement. Except for a
few instances, corresponding chromosomes among the
diploids were, however, shown not to differ significantly
in length. In this case, therefore, chromosome lengths
failed to yield diagnostic mar ke rs related to the six
diploid clones and their phenotypes (yield and quality
potentials).
vi
Corresponding chromosomes among the t.wo triploid
clones wo re howave r shown to be more variable. The
triploid clones similarly had their chromosomes reduced
by as much as 14% in length as compared to their diploid
counterparts. Arm ratios for the haploid chromosome
complements within all the eight clones decreased along
w ith chromosome lengths. Using arm ratios to define
centromeric positions, all the eight clones were shown to
have ch romosomes wh ich we re essent iall y metacentr ics. The
decrease in arm ratios with chromosome length therefore
meant that the shortest ch romosomes with in each comp 1ement
were either perfect or near perfect metacentrics.
Secondary constrictions and satellites were also shown
to be consistently absent in all the eight clones.
Preliminary wo rk on Giemsa staining did not give
positive results and had very limited success in
resolution of chromosomal structures for all the eight
clones.
Description
A thesis submitted in part fulfilment for the award of a Master of Science Degree of Kenyatta University. 1990