Investigation of the Genetic Mechanisms of Resistance to Smut in Sugarcane

Smut caused by a fungus Sporisorium scitamineum is a major sugarcane disease that can cause considerable yield losses. Sugarcane resistance to smut has been demonstrated to be heritable although the genetic determinants of this resistance are unknown. We carried out a number of genetic studies looking at three segregating populations using phenotyping methods that revealed external and internal resistance mechanisms. It was found that some cultivars contain only external resistance while others contain a combination of both internal and external resistance. Screening progeny from a cross for internal resistance it was found that they segregated 1:1 indicating a possible major gene for resistance. A larger number of progeny are in the process of being screened to confirm this. To try and determine what genes are involved in the internal resistance mechanism two methods are being used. Firstly a conventional QTL approach has been initiated which should identify regions of the genome that contain genes that control resistance. This is a long term approach and involves generation of a linkage map. The second approach is to generate a transcription profile of an infected sugarcane bud. One lane of an illumina HiSeq was used to generate RNAseq data from replicated infected and non infected buds from a smut resistant cultivar. This data is in the process of being analysed, any highly expressed genes will if possible be mapped back to the segregating population to determine if they co-locate to the QTL identified.