| Some of these BC1 plants are partially self-fertile and it
is envisaged that, through selfing, novel combinations of chromosomes can
be obtained; for example, several homoeologous and non-homoeologous substitutions
of alien chromosomes in the one plant. These plants may be useful in plant
breeding programs. It has been demonstrated that hexaploid wheat, which is nullisomic for chromosome 5B, will exhibit a considerably increased amount of pairing between homoeologous chromosomes (RILEY & CHAPMAN 1958; SEARS & OKAMOTO 1958). This increase in homoeologous pairing may result from a greater similarity of sites for crossing over and is maximized in hybrids because of the absence of strict homologues (DRISCOLL et al. 1979) Since some of the partially self-fertile BC1 plants are monosomic for chromosome 5B, selfing of these plants is expected to give rise to plants deficient for chromosome 5B. The plants deficient for chromosome 5B should allow exchange of genetic material between wheat and homoeologous alien chromosomes. Further, it is possible that these plants may give rise to more genetic exchanges between wheat and the alien genera because of the expected higher level of univalency than in some other systems of using modifications of chromosome 5B. Initial N-banding studies of the chromosomal complement of BC1 plants of T. aestivum/A. elongatum//T. aestivum, which exhibit unexpected numbers (RODRIGUEZ & MUJEEB-KAZI, 1981), have also disclosed a similar phenomenon ; it appears that these numbers arise from a partially reduced egg cell, pollinated by normal wheat pollen (MUJEEB-KAZI & JEWELL, unpublished). Work is continuing in order to generalize this hypothesis for the Triticinae. |
| <-- Back | | | --> Next |