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Effect of Leaf Width on Responses of Tall Fescue Genotypes to Defoliation Treatment and Temperature Regimes¹

Tall fescue (Festuca arundinacea, Schreb.) genotypes, selected to represent a range in leaf widths, were subjected to several combinations of defoliation treatments and temperature regimes. The effects and interrelationships of characters associated with forage yield were studied with the objective of ultimately developing more meaningful selection indices. Genotypic differences in tillering capacity were associated with leaf width. Number of tillers of genotypes selected for wide, medium, and narrow leaves increased 302, 342, and 406%, respectively, over a 15-week period in the greenhouse. Increasing stubble height from 4 to 12 cm resulted in increased tillering and energy reserves and lower forage yield. Tillering, dry matter yield, and energy reserves increased as number of tillers left uncut at each harvest increased from 0 to 20%, and they tended to remain constant from 20 to 40% intact tillers.

Genetic and temperature effects on tillering were significant at 17/7, 22/12, 27/17, and 32/22 C (day/night) temperature regimes in controlled environment chambers. Maximum tillering occurred at 22/12 C and declined significantly at higher temperatures. A genotype with narrow leaves from North Africa (194-24) produced significantly more tillers than genotypes selected from North American strains and cultivars, particularly at lower temperature regimes. Although leaf width and number of tillers were negatively correlated (r = _0.67), neither was significantly correlated with dry matter yield.

Key Words: Yield components • Tillering • Stubble height • Intact tillers • Energy reserves • Grass breeding • Festuca arundinaceaSchreb

² Formerly associate professor (now research geneticist USDA, ARS. Logan, Utah); research agronomist. USDA. ARS, and professor; and professor, Dep. of Agronomy, Univ. of Missouri, Columbia, MO 65201.

Received for publication December 17, 1976.