AWN Vol 42

Production of intergeneric hybrids is the initial step in exploiting alien genetic variability for crop improvement. The self-sterile F1 hybrids can be advanced to yield BC1 derivatives by pollinating the F1 plants with the same wheat parent or by using a different wheat cultivar. Additional crosses lead to advanced backcross generations, allowing for the production of alien chromosome addition lines, substitution lines, and wheat/alien chromosomal translocations, which through genetic manipulation procedures have the potential of yielding subtle, alien genetic exchanges. Amphiploids derived from F1 intergeneric hybrids significantly ease germplasm distribution and facilitate the systematic development of cytogenetic stocks. Here we report new amphiploids involving T. aestivum and T. turgidum cultivars with some perennial Triticeae and provide cytological/fertility data generated during their maintenance (Table 11). Amphiploid maintenance involves somatic/meiotic cytology, and those that are normal with a high seed set are advanced further in order to obtain larger seed samples for use, distribution, and storage.

Triticum aestivum x perennial Triticeae BC1 self-fertile derivatives with complete and partial synthetic genomes.

R. Delgado, A. Cortés, V. Rosas, and A. Mujeeb-Kazi.

Several intergeneric hybrids were produced and maintained in our program by annual clonal propagation. These hybrids are sources of producing BC1 derivatives by either pollinating the F1 plants with T. aestivum or, if possible, first producing amphiploids and then crossing these to give BC1 progeny. Selfing the BC1 derivatives yields seed set that is indicative of fertility that has a range associated with seed quantity and presumably is influenced by the cytogenetic status of the respective progenies. Such BC1 fertile derivatives form a unique germplasm base with the potential of screening for biotic/abiotic stresses. The alien species involved were Th. intermedium, Th. distichum, Th. elongatum, and Th. scirpeum. Backcrossing F1 hybrids with 2n = 6x = 42 chromosomes or 2n = 5x = 35 chromosomes results in BC1 progeny with 2n = 9x = 63 or 2n = 8x = 56 chromosomes. Selfing of the 63-chromosome derivatives yields 63, or near 63, and 56 chromosome derivatives that we categorize as BC1 fertiles with `complete' genomes (2n = 9x = 63) or with `partial' genomes (2n = 8x = 56), where a genome presumably has been eliminated. Complete genomes generally are maintained after selfing the 56 chromosome BC1 derivatives.

Sixteen BC1 self-fertile intergeneric derivatives are reported (Table 12) of which 15 were produced in our program and one produced elsewhere are maintained. The BC1 derivatives are an alternate germplasm source other than amphiploids for stress screening. The autosyndetic rearrangements during selfed advance of the BC1 plants through `n' generations has the potential to promote genomic modification. Multiple alien disomics that frequently result from selfing lend themselves to genetic manipulation of complex traits.

Selection of selfed derivatives with high seed fertility is a source for the building-up of seed reserves for use in biotic/abiotic stress screening, distribution, and germplasm storage, an area in which work is underway.

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