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Cytology of Bilaterally Derived Tetraploid Red Clover
Author(s) -
Tofte J. E.,
Smith R. R.
Publication year - 1989
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1989.0011183x002900010008x
Subject(s) - pollen , biology , ploidy , population , botany , chromosome , meiosis , red clover , horticulture , genetics , gene , demography , sociology
An interest in increasing heterozygosity in tetraploid (2 n = 4 x = 28) red clover ( Trifolium pratense L.) has led to the use of 2 x ‐2 x (bilateral) crosses for tetraploid production. This study cytologically examined F 2 bilaterally derived tetraploid red clover plants (Bi4 x ) for aneuploid frequency and meiotic chromosome pairing. Cytological results on Bi4 x were compared to colchicine derived, N 2 O derived, and 2 x ‐4 x (unilateral) derived tetraploid populations. In addition, dry pollen morphology of 90 Bi4 x plants was examined. The frequency of aneuploids in Bi4 x was 23%, with chromosome numbers of 25, 26, 27, and 30. Hypoploids (2 n < 28; frequency = 90.48%) were more frequent than hyperploids (2 n > 28; frequency = 9.52%). Chromosome associations in euploid pollen mother cells averaged 0.35 univalents, 5.96 bivalents, 0.14 trivalents, and 3.80 quadrivalents. The difference between euploid chromosome associations and aneuploids was nonsignificant ( x 2 = 2.36; P > 0.50). Observations on dry pollen morphology indicated 78.6% of the Bi4 x population produced more than 80% tetrahedron shaped pollen (typical of n = 2 x = 14 pollen). The frequency of cylindrical shaped pollen (typical of n = x = 7 pollen) ranged from 1% to 90%. The Bi4* plants with a high frequency of cylindrical pollen were crossed to diploid and tetraploid plants. The 2 x ✕ Bi4 x crosses produced no seed, whereas, the 4 x ✕ Bi4 x crosses produced seed (18.13% fertility) suggesting cylindrically shaped pollen in the Bi4 x population reverted to morphology typical of pollen from diploid plants ( n = 2 x = 14). Fiftyfour Bi4 x plants were selfed and seven seeds were obtained from 6177 hand pollinations indicating a high level of self incompatability.