Breeding effects on the cultivar X environment interaction of durum wheat yield

Understanding the effect of past durum wheat breeding activities on the cultivar x environment (C x E) interaction of yield and yield components may guide future breeding strategies. A historical series of 24 cultivars released in Italy and Spain during the 20th century was grown in 13 environments with average yields ranging between 1425 and 6670 kg ha(-1). The most important environmental factors affecting the C x E interaction for yield were reference evapotranspiration before anthesis and water input during grain filling. The response of cultivars to environmental variables in terms of yield and yield components was associated to the allelic composition for the Rht-B1 locus. Improved semi-dwarf cultivars (carrying the Rht-B1b allele) had the best yield performance in environments with high water input after anthesis, while tall cultivars (carrying allele Rht-B1a) were better adapted to environments with high evapotranspirative demand before anthesis and low water input after it. The introduction of the Rht-B1b allele improved the capacity of the crop to respond to water availability during grain filling by increasing the number of grains spike(-1) and grain weight. Yield increases due to breeding caused a loss of stability from the static viewpoint, but not from a dynamic approach based on the superiority measure (P-i). Some semi-dwarf cultivars maintained the levels of yield stability characteristic of the old tall ones. Our results suggest that durum breeding in the 20th century enhanced the response of the crop to environmental improvements. (C) 2015 The Authors. Published by Elsevier B.V.