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Inheritance in Nicotiana tabacum. XI. The Fluted Assemblage

1931; University of Chicago Press; Volume: 65; Issue: 699 Linguagem: Inglês

10.1086/280375

1537-5323

R. E. Clausen,

Light effects on plants

1. By loss of an F-chromosome, probably as a consequence of occasional non-conjunction, N. tabacum var. purpurea produces the monosomic, fluted. 2. When selfed, fluted has produced as further variants the distinctive recessive types, coral and mammoth, both of which have been established in pure lines. 3. From crosses with fluted, both coral and mammoth have been shown to be due to secondary modification of the F-chromosome. 4. Coral and mammoth, when crossed with normal or with each other, produce hybrids of the normal type, which; however, exhibit frequent non-conjunction of the F-chromosomes. 5. By reason of this non-conjunction, F2 and other derivative populations from these crosses contain some haplo-F and triplo-F individuals in addition to the expected classes of offspring. 6. Hybrids of coral with mammoth apparently exhibit no crossing-over between the two modified F-chromosomes. 7. Some of the F2 populations of coral X normal segregated for a recessive pale sterile type, which owes its sterility to extensive non-conjunction of the chromosomes in meiosis. 8. Crosses of pale sterile [female] normal~ [male] produce a variable offspring consisting of numerous monosomic, trisomic and other more complex types of chromosomal variants. 9. Crosses of fluted~ [female] X coral [male] and fluted mammoth [female] X coral [male] have produced four instances of carminecoral variegation, one of which has been shown to arise from fragmentation of the F-chromosome. 10. Carmine-coral variegated plants produce occasional reversionary self-carmine variants, which are identical in flower color but not in vegetative features with normal. 11. Evidence from carmine-coral variegation and reversionary self-carmine indicate that the vegetative features of coral and its distinctive flower color must be due to alteration of different components of the F-chromosome; hence coral must represent some modification of the F-chromosome more extensive than simple factor mutation. 12. Evidently the F-chromosome in the univalent condition is subject to some special forms of genetic modification which occur rarely, if at all, in normal material.