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Environmental factors determining carbon isotope discrimination and yield in durum wheat under Mediterranean conditions

Araus, J.L., Villegas, D., Aparicio, N., Moral, L.F.G. de., El Hani, S., Rharrabti, Y., Ferrio, J.P., Royo, C.
Crop science 2003 v.43 no.1 pp. 170-180
Triticum turgidum subsp. durum, Mediterranean climate, carbon, stable isotopes, crop yield, water uptake, air temperature, temporal variation, climatic factors, plant breeding, Spain
The effect of environment on the relationship between grain carbon isotope discrimination (delta) and yield was studied for durum wheat (Triticum turgidum L. var. durum) under Mediterranean conditions. A group of 25 genotypes was grown under contrasting water regimes in two regions of Spain during three years. The first objective was to determine the environmental factors responsible for the strong positive relationship previously observed between delta and yield across trials. Environmental factors tested were total water input (W(i)), mean temperature, accumulated reference evapotranspiration (ET0), and the ratio W(i)/ET0 during different periods of the crop cycle. Water input during grain filling was the variable most strongly correlated with grain delta and yield across all the trials, as well as across the subset of trials in northeastern Spain. In southeastern Spain, the most drought prone of the two regions, W(i) from sowing to heading explained the most variation in grain delta and yield. The second objective was to study the effect of environment on the relationship between delta and yield across genotypes. No significant correlation was found for trials with a mean yield up to about 2000 kg ha(-1), but the strength of the relationship increased sharply and attained significance in trials yielding 2500 kg ha(-1). When yield above 2500 kg ha(-1) the correlation between delta and yield remained relatively steady and positive, with an r value around 0.5. It is concluded that breeding to raise durum wheat yield in Mediterranean conditions could take advantage of selecting for higher delta only in relatively wet years or under supplementary irrigation.