Relocation of nutrients during stripe rust infection of wheat
V. ROMAN-REYNA (1), J. Rathjen (2), F. Busch (2) (1) Research School of Biology, The Australian National University, Australia; (2) Research School of Biology, The Australian National University, Australia

Stripe rust is one of the major diseases of wheat worldwide. The causative agent is the biotrophic fungus, Puccinia striiformis f.sp. tritici. The fungus enters through the stomata and ramifies throughout the leaf. After 14 days the fungal pustules erupt from the leaf releasing millions of spores. To investigate this interaction at a physiological level, we measured photosynthesis parameters, metabolite changes and host gene expression changes during infection. We found that compatible infections can be divided based on nutrient demand. The first phase comprises germination and parasitic growth of the fungus in the plant. Here the detectable difference between infected and healthy tissue was in host gene expression. During the second phase, all parameters decline in infected leaves. At this stage the plant requires external sources of energy to cope with the increased carbon demand for spore production. We validated these results using detached leaves and by manipulating the nutrient distribution within infected plants by shading some leaves. To compare these results with an incompatible infection, we used a wheat line that has partial resistance due to Lr67 gene, which encodes a sugar transporter. Infected and healthy leaves have the same CO2 assimilation rates, however when older leaves are shaded fungal growth is higher. These results may suggest a resistance mechanism based on controlling shifts in nutrient relocation rather than via canonical mechanisms of immunity

Abstract Number: P1-1
Session Type: Poster