GENOTYPIC DIFFERENCES IN PHOSPHORUS EFFICIENCY OF WHEAT

In an attempt to evaluate whether breeding and selection for high yiel ding capacity did change the P requirements of modern wheat cultivars, the response of two wheat cultivars to different levels of P supply w as investigated. A traditional cultivar (''Peragis'') and a modern cul tivar (''Cosir'') were cultivated in a C-loess low in available P and high in CaCO3 in 120 cm high PVC pots. Shoot and root growth at differ ent developmental stages was compared. The grain yield of the modern c ultivar Cosir was higher at limiting and non-limiting P supply and, th erefore, this cultivar can be considered as more P-efficient than the traditional cultivar. From the results it can be concluded that the ma in factors contributing to the higher P efficiency of the modern culti var are (i) efficient use of assimilates for root growth characteristi cs which enhance P acquisition: smaller root diameter, and longer root hairs, (ii) efficient remobilization of P from vegetative plant organ s to the grains, and (iii) lower P requirement for grain yield formati on because of lower ear number per plant but higher grain number per e ar.