| On the substituting ability of individual alien chromosomes
in common wheat1) P. K. GUPTA Botany Department, The University, Gorakhpur, India The possibility of successful substitution of a single pair of alien chromosomes in the wheat genome is now established. Homoeologous relationships have also been demonstrated between the chromosomes of wheat and Aegilops by RILEY et al. (1966); between wheat and Agropyron by KNOTT (1964), JOHNSON (1966), and JOHNSON & KIMBER (1967); between wheat and Haynaldia by HALLORAN (1966), and between wheat and Secale by RILEY (1964) & GUPTA (1968). Dependence of substitution on the homoeology between the substituted and substituting chromosome has recently been advocated by RILEY (1964), KNOTT (1964) and JOHNSON (1966). This dependence has been described by RILEY et al. (1966) in the form of substituting ability of the alien chromosomes. Two kinds of substituting abilities were envisaged:(a) specific substituting ability, where substitution was specific for the homoeologous chromosomes, and (b) general substituting ability, where substitutions were possible, irrespective of any homoeologous relationship. While the presence of specific substituting ability has been amply demonstrated, the occurrence of general substituting ability is doubted (RILEY et al. 1966). Such conclusions were, however, based on the assumption that successful substitution should give rise to healthy, viable and compensating organism. However JENKINS (1966) and WEINHUES (1960, 1966) had shown that substi tutions can be obtained without any homoeologous relationship between substituted and substituting chromosome. That this may be true was apparent because non-compensating disomic alien substitutions should be possible in the same manner in which 19 non-com- pensating nullisomic-tetrasomic wheat lines were obtained by SEARS (1966). These 19 lines were obtained in only 61 combinations tried. As pointed out by SEARS (1966), the possibility of some genetic relationship between non homoeologues could not be ruled out. |
| 1) Adapted from a thesis submitted and approved for the degree of Doctor of Philosophy of the University of Manitoba, Winnipeg, Canada. |
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