Nitrogen application at anthesis increases barley grain protein by enhancing phloem amino acid mobilisation

BOERO, J. J.; GUTIERREZ BOEM, F. H.; PRYSTUPA, P.; VELIZ, C. G.; CRIADO, M. V.; GOMEZ, F. M.; CAPUTO, C.

Crop and Pasture Science

csiro

Año: 2022

1836-0947

Context: In the malting industry, the low protein content of barley grains is a major issue. A useful strategy to overcome this problem is to complement the initial fertilisation with a foliar application of nitrogen (N) near anthesis.Aims: This study aimed to advance knowledge of the metabolic adjustments displayed by plants grown under common management practices in response to foliar N fertilisation at anthesis.Methods: Field experiments with two different rates of foliar N application near anthesis were performed at three commercial sites under the common practice of each farmer.Key results: Grain protein content increased upon foliar fertilisation in all sites without affecting leaf senescence or N remobilisation efficiency. Barley plants also showed a rapid assimilation of the N applied at anthesis, increasing the leaf N organic pools and the global phloem amino acid mobilisation during grain filling. These results could be attributed to the increase in the gene expression of glutamine synthetase 1 and two amino acid transporters (HvAAP6 and HvAAP7).Conclusions: Foliar N applied was rapidly assimilated and exported with high efficiency to the grain with no negative impact over the contribution of N from vegetative organs. Furthermore, phloem N contribution was shown to be of major importance for grain protein content.Implications: Foliar fertilisation near anthesis is an efficient strategy to correct grain protein content to meet maltsters’ requirements because it did not affect pre-assimilated N remobilisation, and was useful under the different nutrient availabilities explored here (N sufficiency, N deficiency and sulfur deficiency).