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  1. Vol. 14 No. 6, p. 867-872
     
    Published: Nov, 1974


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doi:10.2135/cropsci1974.0011183X001400060028x

Reproduction in Crested Wheatgrass Pentaploids1

  1. Douglas R. Dewey2

Abstract

Abstract

Pentaploid, 2n=35, crested wheatgrasses [Agropyron cristatum (L.) Gaertn.] and related taxa., were derived by crossing natural and induced tetraploids, 2n=28, with hexaploids, 2n=42. The pentaploids backcrossed readily to tetraploids and hexaploids, but they crossed only rarely with diploids, 2n=14. Chromosome numbers in 5x-2x, 5x-4x, 5x-5x, and 5x-6x hybrids ranged from 2n=21 to 25, 2n=28 to 35, 2n=28 to 42, and 2n=35 to 60, respectively. Three hyperoctoploid hybrids—2n=58, 59, and 60—from 5x-6x crosses probably resulted from union of unreduced male gametes, n=42, and reduced eggs, n=16 to 18. The pentaploids produced functional reduced gametes with n=14 to 21 chromosomes, and the gametic chromosome numbers were distributed somewhat normally, with a mean between n=17 and 18. High multivalent associations at metaphase-I in some hybrids were caused by a combination of autoploidy and structural heterozygosity. Fully fertile tetraploid and hexaploid hybrids were recovered immediately from 5x-4x and 5x-6x crosses, respectively. Grass breeders should not find it difficult to transfer genes, chromosomes, or even whole genomes between tetraploid and hexaploid crested wheatgrasses. Genetic transfer between diploid and polyploid races is somewhat more difficult.

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