SYMCROP – Can we prevent symbiotic growth depressions in crops?

This project addresses growth depressions caused by arbuscular mycorrhizal fungi in important crops. The problem is frequently observed in cereals and other grasses in mesocosms and may well result in ‘hidden’ yield losses in the field. Objectives are to test a novel phosphorus limitation hypothesis to reveal mechanisms behind such growth depressions and to investigate methods to mitigate this assumed loss-of-efficiency in P uptake.

 
The majority of plant species form arbuscular mycorrhizas, symbiotic associations, which are particularly important for plant phosphate (Pi) acquisition. Two Pi uptake routes are present in AM plants: the mycorrhizal pathway (MP) and the direct pathway (DP). The hypothesis is that plants can become P limited if the shift to Pi uptake through MP occurs at the expense of function of DP and if this shift is not fully compensated by MP uptake. We will evaluate our results against the conventional explanation for growth depression that AM fungi become carbon draining parasites.

The project addresses a highly important but neglected aspect of AM symbiosis. Ryegrass (negatively responsive to AM) and lucerne (positively responsive) will be our target crops; they are relevant as forage and bioenergy crops and are often grown in mixtures. For the initial studies we will use model plants that are closely related to the target crops and which can be transformed, namely Brachypodium distachyon and Medicago truncatula.

Phosphate uptake by DP and MP will be determined and transgenic methodology will be applied to assess if there is a potential for relieving negative mycorrhizal growth responses (MGRs). This involves the identification of key elements in the interplay between MP and DP e.g. Pi transporters and P signaling genes. The project attempts to mitigate the hypothesized P limitation and the strategy is to manipulate the DP activity by over-expressing some of the positively acting key elements and/or down-regulate potential MP-derived suppressing elements. Plant MGRs obtained in a controlled environment will be verified in the field and will be analysed both at ambient and elevated CO2 concentrations. This will reveal whether the regulatory mechanism(s) governing the plant response to AM are conserved under future climate conditions.

Results will be combined in a model for the regulatory mechanisms underlying MGR in plants. A successfully increased DP uptake in AM plants will help us to provide expression marker genes for breeding plant genotypes where Pi uptake via DP ad MP becomes additive rather than alternative. This would result in more P efficient crops producing higher yields. These innovative approaches aim at eliminating AM-induced growth depressions and will be highly relevant to crop improvement. The development of more P efficient crops is urgently needed due to finite P reserves, increasingly expensive P fertilizers and decreasing soil P levels on farms with no livestock.

Participants
Risø DTU, DLF TRIFOLIUM A/S, The University of Adelaide and Boyce Thompson Institute for Plant Research/Cornell University.

Roles
The project is based at Risø DTU and receives support from our key collaborators: Ingo Lenk and Christian Sig Jensen at DLF TRIFOLIUM A/S. They provide facilities and expertise on genetic transformation of grasses. Sally Smith and Andrew Smith at The University of Adelaide will participate as visiting scientists and Maria Harrison at Boyce Thompson Institute for Plant Research and Cornell University provides access to some key gene sequences and plant mutants.

Resources
The project is funded by The Danish Council of Independent Research | Technology and Production Sciences.

Duration
2011-2014

Emloyees involved
Iver Jakobsen (grant holder and project coordinator), Mette Grønlund (post doc; day-to-day work plans and supervision in the lab), NN (PhD student; transformation of Brachypodium distachyon), Bente Andersen (technician).

 

Siden er opdateret  af   03.02.2011


Iver Jakobsen
Forskningsspecialist
Biosystemer (BIO)
Dir tel 46774154