Differences between wheat cultivars in acquisition and utilization of phosphorus

In an attempt to evaluate whether breeding and selection for high yielding capacity changed the P requirement of modem wheat cultivars. the response of two wheat cultivars to different levels of P supply was investigated. A traditional cultivar (‘Peragis’) and a modern spring‐wheat cultivar (‘Cosir’) were cultivated in a C‐loess low in available P and high in CaCO3 in 120 cm high PVC tubes. In addition and for comparison, nutrient solution experiments were also conducted. Shoot growth, root growth. P uptake. P translocation and P distribution within the shoot at different developmental stages were compared. The grain yield of the modern cultivar ‘Cosir’ was higher at limiting and non‐limiting P supply and. therefore, this cultivar can be considered as more P‐efficient than the traditional cultivar. Grain yield reduction at low P supply was mainly due to an inhibition of tillering and thus lower number of ears per plant, whereas the number of grains per ear was hardly affected. Reduced tillering at low P supply could not be related to P concentrations in the shoot meristematic tissues which were generally much higher than in other plant tissues and kept at an elevated level even at limiting P supply. Root branching (1st order laterals) was reduced at limiting P supply in ‘Cosir’ but not in ‘Peragis’ which, generally, had lower numbers of laterals at the beginning of tillering. From the results it can be concluded that the main factors contributing to the higher P efficiency of the modern cultivar ‘Cosir’ are (i) efficient use of assimilates for root‐growth characteristics which enhance P acquisition: enhanced root branching and thus smaller mean root diameter and longer root hairs, (ii) an efficient P uptake system, (iii) efficient remobilization of P from vegetative plant organs to the grains, and most importantly (iv) lower P requirement for grain yield formation because of lower ear number per plant but higher grain number per ear. Genotypische Unterschiede im Aneignungsvermögen und der Nutzung von Phosphor bei Weizen Wachstum und Ertragsbildung von 2 Sommerweizen‐Sorten wurden bei unterschiedlichem P‐Angebot untersucht, um zu überprüfen, ob die Züchtung auf hohes Ertragspotential zu einer Veränderung des P‐Düngerbedarfes von modernen Weizensorten geführt hat. Hierzu wurde eine traditionelle Sorte (‘Peragis’) und eine moderne Sorte (‘Cosir’) in einem C‐Löß mit niedrigem P‐Angebot und hohem Gehalt an CaCO3 in 120 cm hohen PVC‐Röhrengefäßen kultiviert. Zus