Uses of wheat aneuploids.

The constructive use of aneuploids in any type of study obviously depends on the availability, fertility, and viability of an essentially complete s s of aberrant types. In cultivated wheat (Triticum aestivum, 2n=6x=42) there are available collections of aneuploids unequaled in any other organism. For example, in the cultivar Chinese Spring, Sears (1) produced complete sets of nullisomics, monosomies, trisomies, and tetra- somics, and Sears and Sears (2) have accumulated 41 of the 42 possible telocentrics. Furthermore, many combinations of these aneuploids have been constructed for analyzing specific chromosomal, genetic, and evolutionary situations. Similar but less complete sets of aneuploids in other cultivars have been derived from the Chinese Spring material or have been produced independently. These developments have allowed the investigation of the cytogenetics and evolution of aestivum with an elegance and precision currently unattainable in few if any other higher organisms. The ramifications of these investigations are seen not only in the evolutionary and genetic framework so constructed, but also in actual and potential practical manipulations now available that allow a precise and often predictable genetic control over introduced diversity in the species.