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Cytology and genetics of the wheats and their relatives

By: Material type: ArticleArticleLanguage: English Publication details: 1948. USA : Elsevier,ISSN:
  • 0065-2660
Subject(s): In: Advances in Genetics v. 2, p. 239-270Summary: Because of the economic importance of wheat, the genus Triticum has long been of interest to geneticists. Since the common species of wheat are polyploid, however, only limited genetic progress has been made. Numerous characters have proved dependent on duplicate or triplicate factors, and many others have defied precise analysis. Cytological study of the wheats has been more rewarding. Triticum serves as the classical example of an allopolyploid series. There are three groups of species, with chromosome numbers of n = 7, 14, and 21. With few exceptions, the species within each group have homologous chromosomes; and each of the two polyploid groups apparently has the chromosomes of the group below it, plus seven additional pairs non-homologous with any of those already present. Hybrids of Triticum species are readily made with certain members of the other genera of the sub-tribe Triticinae - namely, Aegilops, Agropyron, Secale, and Haynaldia - and close relationships are indicated with certain species of Aegilops and possibly Agropyron. Correlated cytological and genetical studies of the polyploid wheats have largely been confined to the so-called pentaploid hybrids between hexaploid (n = 21) and tetraploid (n = 14) wheats. Most of the remainder of the cytogenetic work has been done with deficiencies and duplications of whole chromosomes in the hexaploid T. vulgare (common wheat) - work largely limited until recently to deficiency for a particular chromosome, the “speltoid” chromosome.
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Because of the economic importance of wheat, the genus Triticum has long been of interest to geneticists. Since the common species of wheat are polyploid, however, only limited genetic progress has been made. Numerous characters have proved dependent on duplicate or triplicate factors, and many others have defied precise analysis. Cytological study of the wheats has been more rewarding. Triticum serves as the classical example of an allopolyploid series. There are three groups of species, with chromosome numbers of n = 7, 14, and 21. With few exceptions, the species within each group have homologous chromosomes; and each of the two polyploid groups apparently has the chromosomes of the group below it, plus seven additional pairs non-homologous with any of those already present. Hybrids of Triticum species are readily made with certain members of the other genera of the sub-tribe Triticinae - namely, Aegilops, Agropyron, Secale, and Haynaldia - and close relationships are indicated with certain species of Aegilops and possibly Agropyron. Correlated cytological and genetical studies of the polyploid wheats have largely been confined to the so-called pentaploid hybrids between hexaploid (n = 21) and tetraploid (n = 14) wheats. Most of the remainder of the cytogenetic work has been done with deficiencies and duplications of whole chromosomes in the hexaploid T. vulgare (common wheat) - work largely limited until recently to deficiency for a particular chromosome, the “speltoid” chromosome.

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