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Cytological, Morphological, and Agronomic Characteristics of Tall x Giant Fescue Hybrids and Their Amphiploid Progenies¹

F₁ hybrids (2n = 42) of tall fescue (Festuca arundinacea Schreb.) (2n = 42) x giant fescue [Festuca gigantea (L.) Vill.] (2n = 42) were male-sterile, had poor seed-set when backcrossed to tall fescue, and generally were intermediate between parental species for most morphological characters. Sterility of the F₁ hybrids was attributed to meiotic irregularity resulting from lack of chromosomal association of one genome of each parent. Frequency of mean univalents per cell and in mean micronuclei per quartet of F₁s varied from 10.1 to 13.7 and from 2.9 to 6.5, respectively.

Four generations of colchicine-induced amphiploid progenies were male-fertile, and seed-set per panicle was equivalent to that of tall fescue. First-generation progenies varied in chromosome number from 2n = 80 to 84, and in mean micronuclei per quartet from 1.15 to 2.57. Chromosomal pairing of the colchicine-induced progenies was largely bivalent as evidenced by relatively few micronuclei. Chromosome numbers of fourth-generation progenies varied from 2n = 53 to a maximum of 84. Ths occurrence of dodecaploids as the most frequent number in fourth-generation progenies indicates that with rigid selection, rapid progress might be made in securing meiotically stable populations at the 2n = 84 chromosome level.

Although hay yields of fourth-generation progenies compared favorably with ‘Kentucky 31’ tall fescue, both stand and yield declined rapidly after first hay harvest. Poor agronomic performance of the fourth-generation progenies could have been attributed to their narrow gene base. Because the forage quality of the fourth-generation progenies was markedly superior to that of tall fescue cultivars, dodecaploid tall fescue x giant fescue populations appear to have promise as a valuable forage crop.

Key Words: F₁ hybrids • Dodecaploids • Meiotic behavior • Forage quality • Nutritive value index • Perloline • Festuca arundinacea • Festuca gigantea

² Respectively, research agronomist, ARS, USDA, professor of agronomy, research agronomist, ARS, USDA, and professor of agronomy, Dep. of Agronomy, Univ. of Kentucky, Lexington, KY 40506.

Received for publication January 23, 1976.