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1. Gros Michel artificially pollinated by Robusta, both triploid parthenocarpic varieties ofMusa, yielded fifteenF 1 plants of which fourteen are tetraploid and one triploid. The somatic chromosomes of these are described and compared with those of the parents. It is argued that the tetraploidF 1’s are derived from triploid Gros Michel eggs and haploid Robusta pollen.
2. TheF 1 back-crossed with the male parent gave progeny with somatic chromosome numbers ranging from 32 to 44 including triploids, tetraploids and aneuploids. These are thought to have arisen from eggs with chromosome numbers ranging from 21 to 33 fertilised by haploid Robusta pollen.
3. TheF 1 back-crossed to the female parent gave triploids, tetraploids, pentaploids, one heptaploid and aneuploids. These seedlings it is argued arose from either triploid or diploid Gros Michel eggs fertilised byF 1 pollen ranging in chromosome number from 11 to 22. The heptaploid was probably formed from an egg with a doubled chromosome complement (66).
4. The onlyF 2 plant proved to be an aneuploid with 34 somatic chromosomes.
5. The foregoing conclusions are supported by a statistical analysis of pollen grain size in the parents andF 1, based on the assumption that that size varies as the pollen chromosome number.
6. Discrepancies, such as the absence of hexaploid seedlings in the back-cross to Gros Michel, are attributed to the selective action of differential pollen tube growth.
KeywordsChromosome Number Chromosome Count Somatic Chromosome Chromosome Constitution Secondary Constriction
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- Cheeseman, E. E. (1932). “Genetic and cytological studies ofMusa. I. Certain hybrids of the Gros Michel banana.”J. Genet.26, 291–312.Google Scholar
- —— (1933). “Mutant types of the Dwarf banana.”Trop. Agric., Trin.,10, 4–5.Google Scholar
- -- (1934). “Principles of banana breeding.”Mem. Imp. Coll. Trop. Agric. Trinidad, No. 3, 20 pp.Google Scholar
- Cheeseman, E. E., Wardlaw, C. W. andSpencer, C. L. (1933). “The Cavendish group of banana varieties with special reference to Lacatan.”Trop. Agriculture, Trin.,10, 218–220.Google Scholar
- Graner, E. A. (1934). “Observações sobre o numero de chromosomios na bananeira.”Rev. Agric., Brazil,9, Nos. 7–8.Google Scholar
- Humphrey, L. M. (1934). “The meiotic divisions of haploid, diploid and tetraploid tomatoes with special reference to the prophase.”Cytologia,5, 278–300.Google Scholar
- Jørgensen, C. A. (1928). “The experimental formation of heteroploid plants in the genusSolanum.”J. Genet.19, 133–211.Google Scholar
- Larter, L. N. H. (1935). “Plant breeding. Report of the Government Geneticist.”Ann. Rep. Dept. Agric. Jamaica, 1933, p. 23.Google Scholar
- -- (1935a). “Plant breeding. Report of the Government Geneticist.”Ibid. 1934 (in Press).Google Scholar