Genotypic variability in wheat for preference of NH4+, NO3- or NH4+NO3

Cathryn O’Sullivan1, Jairo Palta 1, Mark Farrell2, Karen Treble1.

1 CSIRO Agriculture, 147 Underwood Ave, Floreat, WA, 6014, http://www.csiro.au/en/Research/AF, [email protected]

2 CSIRO Agriculture, Waite Road, Urrbrae SA 5064, http://www.csiro.au/en/Research/AF, [email protected]

Abstract

Improving the nitrogen (N) uptake efficiency (NUpE) of wheat has the potential to offer significant economic gains to growers and improvement in environmental quality. One way to improve NUpE may be by matching wheat genotypes which have greater uptake efficiency for NH4+ or NO3- to soil types that favour the production of one of these N forms over the other. Surprisingly there has been little previous research investigating the genotypic variation in wheat for preference of different forms of N. The aim of this study was to screen a range of wheat cultivars and landraces for their ability to uptake N and produce biomass on NH4+, NO3- and a mixture of NH4NO3. To date, 21 wheat genotypes have been grown hydroponically on three different nutrient solutions providing N as NH4+, NO3- or NH4NO3. The nutrient solutions were all supplemented with a nitrification inhibitor, well aerated and pH controlled. At 8 weeks after sowing (post-tillering for all lines) the shoots were harvested and leaf area, shoot biomass and N content measured.

There is significant variation among the genotypes tested in their ability to uptake N and produce biomass on different N sources. Several cultivars, including Frame and Gamenya, produced more biomass with higher N content on NO3-. Others, including Yitpi and Wyalkatchem performed best on NH4+ while others, including Halberd and Condor, performed better on NH4NO3 than on either NO3- or NH4+. This information is critical for further research to determine whether it is possible to improve NUpE by targeting genotypes with differing N preferences to soil types where a particular N form is likely to occur.