Summary
Two selected hexaploid F1 clones from the cross Solanum acaule x S. bulbocastanum were intercrossed and the resulting hybrid plants pollinated with the diploid species S. phureja, in order to obtain tetraploid triple hybrids with the same ploidy level as S. tuberosum cultivars (2n=4x=48).
Apart from three trihaploids a large population of triple hybrids was obtained, showing chromosome mosaicism in root tip cells (euploid + hypoploid chromosome numbers) and a uniform, mostly hypoploid chromosome number in the pollen mother cells. It is demonstrated that somatic chromosome elimination in the early stages of development is the most probable cause.
From detailed pachytene observations as well as from the chromosome associations observed at metaphase I it is evident, that there is normal pairing between the four genomes in the triple hybrids. Although S. bulbocastanum is a quite distinct species with a rigid crossability barrier with S. phureja, the chromosomes of these two species appear to have a high degree of homology. Especially the formation of quadrivalents involving all twelve groups of four homeologous chromosomes, indicated that the four parental genomes (two from S. acaule, one from S. bulbocastanum and one from S. phureja) are not differentiated to the extent of affecting normal pairing and chiasma formation. These results support the view, that the transfer of valuable characters from S. bulbocastanum to S. tuberosum cultivars is feasible even when these characters are polygenically controlled.
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References
Dionne, L. A., 1963. Studies on the use of Solanum acaule as a bridge between Solanum tuberosum and species in the Series Bulbocastana, Cardiophylla and Pinnatisecta. Euphytica 12: 263–269.
Gabert, A., 1963. Factors influencing the frequency of haploids in the common potato (Solanum tuberosum L.). Ph.D. thesis, Wisconsin State University.
Hermsen, J. G. Th., 1966. Crossability, fertility and cytogenetic studies in Solanum acaule x Solanum bulbocastanum. Euphytica 15: 149–155.
Hermsen, J. G. Th. & Boer, A. J. E. de, 1971. The effect of colchicine treatment on Solanum acaule and S. bulbocastanum; a complete analysis of ploidy chimeras in S. bulbocastanum. Euphytica 20: 170–179.
Hermsen, J. G. Th. & Ramanna, M. S., 1969. Meiosis in different F1-hybrids of Solanum acaule Bitt x S. bulbocastanum Dun and its bearing on genome relationship, fertility and breeding behaviour. Euphytica 18: 27–35.
Howard, H. W., & Swaminathan, M. S., 1952. Species differentiation in the Section Tuberarium of Solanum with particular reference to the use of interspecific hybridization in breeding. Euphytica 1: 20–28.
Ross, R. W., Dionne, L. A., & Hougas, R. W., 1967. Doubling the chromosome number of selected Solanum genotypes. Eur. Potato J. 10: 37–52.
Sachs, L. 1952. Chromosome mosaics in experimental amphiploids in the Triticinae. Heredity 6: 157–170.
Yeh, B. P., & Peloquin, S. J., 1965. Pachytene chromosomes of potato (Solanum tuberosum Group Andigena). Am J. Bot. 52: 1014–1020.
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Ramanna, M.S., Hermsen, J.G.T. Somatic chromosome elimination and meiotic chromosome pairing in the triple hybrid 6x-(Solanum acaule × S. bulbocastanum) × 2×-S. phureja . Euphytica 20, 470–481 (1971). https://doi.org/10.1007/BF00034200
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DOI: https://doi.org/10.1007/BF00034200