Leaf photosynthesis during grain filling under mediterranean environments: are barley or traditional wheat more efficient than modern wheats?

Abstract

Barley is one of the most popular crops in dryland agricultural systems of Mediterranean areas, where it is assumed that barley, or traditional wheat cultivars, performs better than modern wheat under low-yielding conditions. It was tested whether variations in net leaf photosynthetic rate (PN) during grain filling provide any basis for the potential better performance of barley and traditional wheat compared to modern wheats in Mediterranean areas. Two groups of field experiments were conducted in Agramunt (NE Spain) during 2005/06 (06) and 2006/07 (07) growing seasons combining low and high nitrogen (N) availabilities under rain-fed and irrigated conditions. Cultivars used in the first group of experiments were a traditional (Anza) and a modern (Soissons) wheat, whilst in a second group of experiments, a wheat (Soissons) and a barley (Sunrise) modern cultivars were used. Both wheat cultivars showed a similar PN during grain filling but higher than that of the modern barley cultivar. Differences between species in PN were maximized under high-yielding conditions. There were no differences between cultivars in instantaneous water-use efficiency. The barley cultivar showed a higher specific leaf area, but lower N content per unit of leaf area, than wheat. Photosynthetic nitrogen-use efficiency was similar between the traditional and the modern cultivar but lower than barley. Decreases in PN after anthesis were not exactly observable in SPAD measurements. In conclusion, we found no consistent differences between cultivars in terms of post-anthesis photosynthetic activity to support the assumption of better performance under Mediterranean farm conditions of traditional wheat or barley against modern wheat.