SYNTHETIC POLYPLOIDS OF TRAGOPOGON MISCELLUS AND T-MIRUS (ASTERACEAE): 60 YEARS AFTER OWNBEY'S DISCOVERY

[摘要]：In plants, polyploidy has been a significant evolutionary force on both recent and ancient time scales. In 1950, Ownbey reported two newly formed Tragopogon allopolyploids in the northwestern United States. We have made the first synthetic lines of T. mirus and T. miscellus using T. dubius, T. porrifolius, and T. pratensis as parents and colchicine treatment of F-1 hybrids. We also produced allotetraploids between T. porrifolius and T. pratensis, which are not known from nature. We report on the crossability between the diploids, as well as the inflorescence morphology, pollen size, meiotic behavior, and fertility of the synthetic polyploids. Morphologically, the synthetics resemble the natural polyploids with short- and long-liguted forms of T. miscellus resulting when T. pratensis and T. dubius are reciprocally crossed. Synthetic T. mirus was also formed reciprocally, but without any obvious morphological differences resulting from the direction of the cross. Of the 27 original crosses that yielded 171 hybrid individuals, 18 of the lineages have persisted to produce 386 S-1 progeny: each of these lineages has produced S-2 seed that are viable. The successful generation of these synthetic polyploids offers the opportunity for detailed comparative studies of natural and synthetic polyploids within a nonmodel system.

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