Background/context:

This project set out to better understand disease resistance genes in sugarcane and sorghum. The project was prompted by an orange rust epidemic in 2000, which caused heavy yield and varietal losses to the Australian sugar industry.

 Aim:

To be better prepared for future epidemics, the project attempted to (i) identify and clone disease resistance (R) genes from sugarcane and sorghum and (ii) generate assays which allow more rapid analysis of functional disease resistance genes from these species. The latter goal is particularly important in sugarcane where the complex genetic makeup makes mapping more difficult than in diploid species like sorghum. In addition, polyploids such as sugarcane appear to have a higher than normal number of pseudogenes, so techniques to identify functional genes amongst a large number of pseudogenes would be advantageous.

Major Outcomes:

This project identified and cloned disease resistance genes from sorghum. Genomic DNA libraries from sorghum were constructed, cosmid clones containing the sequence of interest were identified, and the gene sub-cloned and sequenced. The gene encoded a typical plant disease resistance (R) gene very similar to the maize RP1D gene. Importantly, the gene was only present in rust resistant cultivars. However, no sorghum complementation work has been conducted to conclusively show that this gene confers rust resistance. 

Using the putative sorghum rust resistance gene, rapid assays to assess R gene functionality were engineered. Proteins that were able to interact with our putative rust resistance protein were studied and three different sorghum proteins that were able to interact with the putative sorghum rust resistance genes were identified. More research must occur to test if these interactions actually occurred in plants. If the interactions were bone fide it could lead to advances in R gene signaling networks and possibly rapid isolation of functional R genes.

For more information contact:

Dr Stevens Brumbley
Bureau of Sugar Experiment Stations
Phone: +61 (0)7 3331 3370
Email: sbrumbley@bses.org.au