Sub-theme 3e - Roots balance parasitic nematodes with nodulation by N2-fixing rhizobia


Specific sub-theme contributors:

Associate Professor Ulrik Mathesius and Professor David Bird

Plant-parasitic nematodes (PPN) are the most damaging group of essentially uncontrollable plant pathogens. Alone they reduce global agricultural production by 10-15%, but in conjunction with other stresses, losses can be much more severe. Disease from PPN in chickpea can reach 100% in parts of Australia (Murray & Brennan, 2012). Control currently is limited to a small number of resistant varieties, combined with crop rotation (GRDC, 2014). We do not yet understand what determines the attraction of nematodes to host roots, which molecular pathways are targeted in the host, and how PPN causes pathology (yield loss). These areas will be the focus of our research. Intriguingly, parasitic nematodes target the same niche in the root as symbiotic rhizobia on their host root, and activate partially overlapping response pathways (Weerasinghe et al., 2005). PPN preferentially infect root nodules, reducing N2-fixation (Castillo et al., 2008), so targeting nematode pests is likely to have additional benefits for N2-fixing symbioses. While most studies have focused on infection of plants with one organism at a time, our research will target the interaction of parasitic nematodes and symbiotic rhizobia with their host plants as a basis for rational strategies for maximising nodulation/nitrogen fixation and minimising yield loss from parasitic nematodes. Identification of new chemical signals exuded from the root could be used to alter nematode behaviour in the soil. Our goal is an integrated understanding of the mechanisms that plants use to balance infection by multiple parasites.

Strategies for optimising the timing of the inoculation of crops with rhizobia; breeding towards nematode resistance (e.g., identifying markers) with minimal effect on nodulation.

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