Maize farming requires high amounts of N fertilizer, with adverse environmental effects and insufficient agronomic sustainability. Certain maize genotypes can be colonized endophytically by atmospheric nitrogen (N2)-fixing bacteria, but the agronomic potential of endophytic N2-fixation is not fully exploited. Our hypothesis is that a scientific understanding of the mechanisms controlling these endophytic N2-fixing associations combined with an assessment of maize genetic diversity and specificity with regards to this interaction could be useful to optimize endophytic N2-fixation and exploit it in agriculture. The aim of the project is thus to better understand the interactions between bacterial endophytes fixing N2 and maize, in order to identify and select maize genotypes that will be able to use the fixed N more efficiently and thus will be less dependent on mineral N fertilization. This will be achieved by developing a multidisciplinary approach integrating molecular physiology, the assessment of whole-plant N responses to the endophytic interaction, molecular plant-microbe ecology and agronomy. We will characterize both at the physiological and molecular levels the atmospheric N2-fixing endophytic interaction using a large-scale integrated transcriptomic, proteomic and metabolomic approach implemented with two established Herbaspirillum and Azospirillum models of N2-fixing endophytic bacteria and 19 representatives of European and American maize genetic diversity. This will allow identifying the genetic and physiological determinants required for an efficient N2-fixing endophytic association. Such study, combined to a genome-scale metabolic modelling approach, will then help obtaining an integrated view on the plant’s response to the endophytic interaction and on its adaptation to temperate climatic conditions.
A molecular screening will also be conducted to obtain effective endophytic N2-fixing bacteria for agronomic improvement of maize cultivation at lower N input under temperate pedoclimatic conditions. To this end, we will implement a novel molecular screening strategy, using not only microbial traits but also the plant biological markers of the ability of the plant to utilize the fixed N more efficiently.
Production of innovative fertilizers based on inoculant technology will be then undertaken to assess under agronomic conditions, if the maize genotypes exhibiting the best endophytic N2 fixation also exhibit improved performance in terms of biomass and grain production. Such an agronomic evaluation will also be conducted with commercial hybrids known for their high performance under reduced N fertilization.
The project focuses on maize, a crop of major economic importance both in France and worldwide. Maize is particularly relevant for this project for four reasons. First, it has a huge genetic diversity, allowing the improvement of both its agronomic and environmental performances in terms of N fertilizer usage. Second, maize is also a model crop particularly suited to perform integrated agronomic, physiological and molecular genetic studies during the whole plant developmental cycle. Third, many maize genotypes are colonized endophytically by N2-fixing bacterial endophytes. Thus, deciphering the relationships between maize physiological status and the provision of “free” N by the bacterial endophytes will deliver science to underpin and implement novel agricultural strategies aimed at reducing the use of N mineral fertilisers in maize farming, which will be facilitated by the industrial development in this project of fertilizer micro-granules serving as carriers for N-fixing endophytic inoculant.
INRA Institut Jean-Pierre Bourgin (Laboratoire public)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
INRA Institut Jean-Pierre Bourgin
AGRO INNOVATION INTERNATIONAL
Laboratoire d'Ecologie Microbienne
Help of the ANR 486,985 euros
Beginning and duration of the scientific project: - 48 Months