Description
Common dallisgrass, Paspalum dilatatum Poir., an important warm season forage grass, is an obligate apomict with 50 chromosomes which associate as 20 bivalents and 10 univalents during meiosis. Because efforts to improve the grass have not been successful, a phylogenetic investigation was initiated to identify the progenitors of common dallisgrass in an effort to circumvent the apomictic barrier to improvement. The genomic composition has been determined for four dallisgrass biotypes: yellow-anthered (2n=4x=40) IIJJ; common (2n=5x=50) IIJJX; Uruguayan (2n=6x=60) IIJJXX; and Uruguaiana (2n=6x=60) IIJJXX. While the source of the X genome is unknown, the genes controlling apomixis are on at least one of the X chromosomes because biotypes with 10 or more X chromosomes are apomictic. However, when four or five of the X chromosomes are missing, apomixis is not expressed. This suggests that apomixis is controlled by more than one gene and at least one of the X chromosomes must be present for apomixis to be expressed.
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Phylogenetics of Apomictic Common Dallisgrass (Paspalum Dilatatum)
Common dallisgrass, Paspalum dilatatum Poir., an important warm season forage grass, is an obligate apomict with 50 chromosomes which associate as 20 bivalents and 10 univalents during meiosis. Because efforts to improve the grass have not been successful, a phylogenetic investigation was initiated to identify the progenitors of common dallisgrass in an effort to circumvent the apomictic barrier to improvement. The genomic composition has been determined for four dallisgrass biotypes: yellow-anthered (2n=4x=40) IIJJ; common (2n=5x=50) IIJJX; Uruguayan (2n=6x=60) IIJJXX; and Uruguaiana (2n=6x=60) IIJJXX. While the source of the X genome is unknown, the genes controlling apomixis are on at least one of the X chromosomes because biotypes with 10 or more X chromosomes are apomictic. However, when four or five of the X chromosomes are missing, apomixis is not expressed. This suggests that apomixis is controlled by more than one gene and at least one of the X chromosomes must be present for apomixis to be expressed.
