• Abbas H. Ar-Rushdi

      Articles written in Journal of Genetics

    • Inheritance inNicotiana tabacum XXVI. Sterility genes from tomentosae species - With plate 1 and three text-figures

      Abbas H. Ar-Rushdi

      More Details Abstract Fulltext PDF

      The sesquidiploidsN. tabacum-tabacum-setchellii andN. tabacum-tabacum-tomentosa ‘Acomayo’, despite having normal embryo-sacs and good pollen, were completely sterile in terms of seed setting.

      Sterility was found to be due, primarily, to a retarded rate of pollen-tube penetration which resulted in bursting of tube-ends and their ultimate failure to reach the ovary.

      A single dominant complementary gene (Tr1) was found inN. setchellii which was responsible for the sterility. The other complementary locus is present in thesylvestris subgenome ofN. tabacum as well as inN. sylvestris in the homozygous dominant condition.

      Tr1’ was introduced intoN. tabacum by a series of backcrosses and was located in the ‘L’ chromosome. Its introduction was found to be associated with pollen dimorphism.

      The significance of the two systems of genic sterility hitherto found in the progenitors ofN. tabacum and the restrictions imposed by them on the origin and establishment ofN. tabacum were discussed. It was concluded thatN. tabacum arose as an amphicliploid involvingN. sylvestris and a recombination product which was free from both, genic sterility systems, obtained from a cross between two sterility types in the Tomentosae.

      These investigations were made in the laboratories of the Department of Genetics at the University of California. They were facilitated by a scholarship from the Government of Iraq.

      The writer wishes to express his indebtedness to Prof. R. E. Clausen, who suggested the problem and provided the material for its execution. His continuous advice and criticisms were essential in the conduct of the study.

      Thanks and gratitude are due to Dr D. R. Cameron for his personal supervision throughout the investigation and during the preparation of the manuscript.

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