Rhizobacterial benefits for adaptation of wheat to nitrogen limitation and drought – BacterBlé

TASK 1. SCREENING OF WHEAT ACCESSIONS FOR PGPR INTERACTION. The objective is to screen wheat diversity for the ability to interact with PGPR. A collection of 200 bread wheat accessions from 38 countries sub-sampled from the INRA worldwide bread wheat core collection will be used.

TASK 2. IDENTIFYING CHROMOSOMAL REGIONS INVOLVED IN WHEAT-PGPR INTERACTIONS. The objective is to identify molecular markers and candidate genes linked to wheat response to PGPR interactions. The chromosomal regions associated with a PGPR response will finally be compared with agronomic data available for the 200 accessions grown in a field network of different sites.

TASK 3. ASSESSING WHEAT INTERACTIONS WITH INDIGENOUS PGPR POPULATIONS IN THE FIELD, INCLUDING UNDER SUBOPTIMAL ABIOTIC CONDITIONS. The objective is to assess the agronomic performance of 10 selected wheat genotypes (obtained from Task 1) under experimentally-managed suboptimal abiotic conditions and their effects on indigenous PGPR-containing populations potentially involved in wheat stress alleviation.

The procedures for labelling PGPR by fluorescence markers have been implemented, so as to be able to visualize interaction of PGPR with plant. A first series of screening of wheat varieties has been done.

The main future prospect is to continue with the tasks of the project.

One review in an international journal:
Cormier, F., J. Foulkes, B. Hirel, D. Gouache, Y. Moënne-Loccoz, J. Le Gouis. 2016. Breeding for increased nitrogen use efficiency: a review for wheat (Triticum aestivum L.). Plant Breeding 135:255–278. [Partners: EM + GDEC + Biogemma]

Global change is a new challenge for sustainable agriculture. We aim at understanding/exploiting plant growth-promoting rhizobacteria (PGPR) to maintain wheat yield despite reduction of nitrogen fertilisers and irrigation water, by enabling a PGPR-based wheat breeding strategy. The rationale is that indigenous PGPR populations occur in most temperate wheat soils, but (i) wheat accessions differ in the ability to benefit from PGPR and (ii) past breeding for high-input conditions has overlooked these beneficial interactions.
The objectives are to (i) screen a large panel of wheat diversity based on induction of gene expression in emblematic PGPR strains, (ii) determine wheat chromosomal regions involved in the interactions between roots and emblematic PGPR strains, (iii) validate these genetic determinants and PGPR benefits in controlled environments and (iv) assess their significance under combined abiotic constraints (nitrogen and water limitations) in field experiments. This will facilitate the breeding of genitor varieties with a successful interaction with PGPR by providing molecular markers linked to chromosomal regions associated to this interaction.
The project is organized in three experimental Tasks. The first task aims at identifying wheat genotypes triggering the expression of key phytostimulation genes in PGPR. A collection of 200 bread wheat accessions mainly sub-sampled from the INRA bread wheat core collection of 372 accessions (372CC) will be screened, using an original phenotyping assay, for induction of bacterial genes important for successful functioning of Azospirillum and Pseudomonas PGPR strains on roots. Results will be validated using complementary methodology on a subset of 20 wheat lines showing a contrasted behavior with PGPR strains.
The second task aims at identifying wheat genomic regions involved in plant × PGPR interactions. Candidate genes and physiological markers relevant to characterize the plant’s responses to Azospirillum and Pseudomonas PGPR (which are widely found in French arable soils) will be identified by transcriptomics (combined with metabolomics), particularly under N and water limitations. The candidate genes will be validated using quantitative RT-PCR, and new SNP markers of the wheat genome will be developed for about 100 of the most relevant genes. An association genetics approach will be carried out using PGPR gene induction data from Task 1, and wheat accessions will also be compared based on agronomic performance data already available.
The third task will assess in the field the wheat lines selected in Task 1 in terms of their ability to (i) interact with functional microbial populations containing PGPR strains that occur naturally in soils and (ii) adjust to nitrogen limitation occurring alone or in combination with drought. Multilocal field experiments will be used.
The CNRS Lyon partner (coordinator) has long-term experience in the genetics of Azospirillum and Pseudomonas PGPR strains and their modes of action, and has expertise in molecular analysis of indigenous PGPR populations and rhizosphere functioning. The INRA Clermont-Ferrand partner is a major actor in wheat genomic research and association genetics, and has expertise in the characterisation of wheat genetic resources and physiological aspects of yield and seed quality. Finally, Biogemma is a leading European plant biotechnology company with long standing expertise in wheat genetics and transcriptomics.
Altogether, the partners’ skills and complementary expertise combined with the genetic and genomic resources available for wheat ensure a successful project that will bring new insights into key plant-PGPR interactions and enable a novel PGPR-based wheat breeding strategy adapted to global change conditions.