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WHEAT

Changes in Yield and Carbon Isotope Discrimination of Italian and Spanish Durum Wheat during the 20th Century

^a IRTA, Durum Wheat Breeding, Centre UdL-IRTA, Rovira Roure, 191, 25198 Lleida, Spain
^b Dep. de Fisología Vegetal, Facultad de Ciencias, Instituto de Biotecnología, Univ. de Granada, 18071 Granada, Spain

^* Corresponding author (conxita.royo{at}irta.es).

This study evaluates the breeding of durum wheat (Triticum turgidum L. var. durum) during the 20th century with respect to yield and grain carbon isotope discrimination (), and their relationship with plant height, harvest index (HI), days from sowing to anthesis, and days from anthesis to maturity. Twenty-four cultivars released before 1945 (old), between 1950 and 1985 (intermediate), and between 1988 and 2000 (modern), and previously characterized by whether dwarfing genes were present (semidwarf) or absent (tall), were selected from germplasm obtained in Italy and Spain. Experiments were conducted in six environments with average yields ranging from to 2113 to 4827 kg ha^–1. The total absolute genetic gain in yield across countries from before 1945 to 2000 was 20 kg ha^–1 yr^–1 (51% of increase), which represents a relative genetic gain of 0.61% yr^–1. Yield gains led to a loss of stability. The mean increase in ¹³C was 6% (0.014 yr^–1 or 0.09% yr^–1). Early heading and a long grain-filling period were correlated with high yields in the tall cultivars. Increased plant height and low ¹³C values were associated with high yields for the semidwarf cultivars, while a long grain-filling period was not advantageous for semidwarf cultivars.

Abbreviations: ¹³C, grain carbon isotope discrimination • CIMMYT, International Maize and Wheat Improvement Center • HI, harvest index • PDB, Pee Dee belemnite

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Received for publication February 12, 2007.