Cytogenetic studies of some Kenyan tea clones (camellia Sinensis) l.o. kuntze) karyotype and ploidy.
Wachira, Francis Nyamu
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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.
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