Cell and nuclear volumes were determined for 17 species and plant types in the genus Gossypium. All species and types, except one, showed a significant positive association between nuclear and cell volume. The overall species r-value (0.694) for cell and nuclear volume is highly significant and positive. For the 17 plant forms, the r-values for association of DNA content and nuclear volume and for association of DNA content and cell volume are 0.625 and 0.655, respectively, and both are highly significant.
Gossypium bickii Prokh. is distinct from the C genome species, although it was tentatively placed in this genome. A comparison of the karyotypes of G. bickii and G. sturtianum Willis separates G. bickii sharply from G. sturtianum, the standard species for the C genome. Karyotypic differences are evident in centromere position of the chromosomes, chromosome size, and the lack of satellites or secondary constrictions in G. bickii. A clear separation of G. bickii from G. sturtianum and other Gossypium species is also demonstrated in previous studies of phenetic analysis, flower flavonoids, DNA content, and electrophoresis of seed proteins, esterases, leucine aminopeptidases, and catalases. G. bickii is placed in a new G genome and is assigned to the 2G1 subgenome.
From 1946 to 1975, 166 monosomic plants of Gossypium hirsutum L. were placed in the monosome testing program at Beasley Laboratory. The 85 that have been identified have been deficient in one of the following chromosomes: 1, 2, 4, and 6 from the A subgenome; 16, 17, and 18 from the D subgenome. These monosomes came from irradiation treatments, translocations, tertiary monosomes, duplication‐deficiencies, cytological combinations, trisomics, other aneuploids desynaptics, other Gossypium species, cultivars, and breeding stocks.
A detailed karyotype of Gossypium sturtianum Willis is presented to establish the C genome karyotype for comparison with other Australian wild species of cotton. Gossypium sturtianum has one chromosome with a median centromere, eight with slightly submedian centromeres, two with submedian centromeres and two with highly submedian centromeres. Chromosomes 8 and 9 have satellites. The total complement length is 75.04 micrometers.
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