LEAF SENESCENCE AND N UPTAKE PARAMETERS AS SELECTION TRAITS FOR NITROGEN EFFICIENCY OF OILSEED RAPE CULTIVARS

Abstract

The cultivation of N-Efficient oilseed rape cultivars could contribute to a reduction of the large N balance surpluses of this crop. To facilitat the breeding process of N-efficient cultivars, the identification of secondary plant traits correlating with N efficiency is necessary. The objectives of this study were to investigate leaf senescence and N iptake parameters of oilseed rape cultivars and doubled haploid (DH) lines with contrasting N efficiency in a short-term nutrient solution experiment and to relate these results to their performance in field experiments. In the nutrient solution experiment, genotypes differed in leaf senescence of fully expanded leaves and maximum N uptake reate seemed to have cintributed to delayed leaf senescence by enhancing N accumulation in leaves. Also in the field experiments, genotypes differed in leaf senescence after floweing at limiting N supply. Additionally, the most N-efficient DH line was able to adapt leaf photosynthetic capatcity to the low-light conditions in the canopy during flowering. N efficiency (grain yield at limiting N supply) was positively correlated with delayed leaf senescence both in nutrient solution and field experiments. It is concluded that important leaf and root traits in N-efficient cultivars are expressed in short-term nutrient solution experiments, which may facilitate the selection of N-efficient cultivars.