Cultivar differences in nitrogen translocation in wheat

Abstract

The translocation efficiency of plant nitrogen to the grain was examined in six lines of bread wheat (Tvtticum aestivum L.) under four levels of soil nitrogen (48, 556, 810 and 1065 ppm). Translocation efficiency, both within the primary tiller and within the whole plant, was significantly different between cultivars; the within-tiller value was higher than the corresponding whole-plant value for each cultivar. There were marked differences in trends in translocation efficiency between certain cultivars as the soil nitrogen availability increased. A reasonably close positive correlation (r = + 0.74, P < 0.01) existed between the within-tiller and whole-plant values for translocation efficiency over the four nitrogen levels. It is suggested that wheat breeders use within-main-tiller translocation efficiency of nitrogen, in parental or crossbred selection to increase grain nitrogen yield in wheat. Because nitrogen translocation efficiency varied with soil nitrogen level, such selection would need to be conducted under soil nitrogen levels appropriate to field conditions. The relationship between total plant dry matter and total grain nitrogen across cultivars and nitrogen levels was not close (r = +0.41, P < 0.01), which suggests that a good potential exists for selecting for increased total grain nitrogen levels in wheat at existing levels of total dry matter production. The implications of these findings for further genetic and biochemical study of nitrogen metabolism in wheat, are outlined.