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Genetic Variability and Heritability of Certain Forage Quality and Mineral Constituents in Lolium-Festuca Hybrid Derivatives¹

Breeding tall fescue (Festuca arundinacea Schreb.) cultivars with high digestibility and high nonstructural carbohydrate content and the proper balance of potassium (K), calcium (Ca), and magnesium (Mg) may overcome many of the seasonal problems of cattle grazing the species. The objective of this paper is to present estimates of genetic variability and heritability of digestibility, water-soluble carbohydrates, K, Ca, Mg, and the K/(Ca + Mg) ratio and their association in selected Lolium-Festuca hybrid derivatives. Twenty-eight parental clones were evaluated in a spaced plant nursery, and their polycross progenies (pep) in seeded rows in Madison County, Kentucky. Additionally, the pcp were evaluated in sod plots in Fayette County, Kentucky. A combined analysis of variance of parents and pep at both locations for forage quality and mineral constituents showed highly significant differences for these characteristics among selections, generations, years, and their interactions. Broad sense heritahility estimates among parental clones were high for all constituents, indicating that a considerable portion of the total variability was genetic. Heritability estimates obtained from regression of pcp on parents were relatively high when parents and pcp were grown in close proximity for all constituents except K and the K/(Ca Mg) ratio. When parents and pcp were grown in widely different environments, the heritability estimates were low for all constituents. Thus, breeding materials should be evaluated for forage quality and mineral constituents in a minimum of two locations with widely different environments. Predictions of response to selection were disappointingly small for all characters. The data suggest that progress in breeding for low tetany potential in these materials, while possible, may require considerable time and effort.

Key Words: Digestibility • Water soluble carbohydrate • K • Ca • Mg • K/(Ca + Mg) • Hypomagnesaemia • Broad sense heritability • Narrow sense heritability • Tall fescue • Ryegrass • Forage grass breeding

² Research agronomists, AR, SEA, USDA; associate professor and professors, Dep. of agronomy, Univ. of Kentucky, Lexington, KY 40546.

Received for publication September 2, 1980.