A differential expression study on the Saccharum spp.-Sporisorium scitamineum pathogenic interaction was carried out in the susceptible Ja60-5 and the resistant M31/45 genotypes. Using cDNA-AFLP analysis, a total of 64 transcript-derived fragments (TDFs) was found to be differentially expressed, with the majority (67.2%) of the differential TDFs up-regulated in the resistant M31/45 cultivar. The plant response against S. scitamineum infection was complex, representing major genes involved in oxidative burst, defensive response, ethylene and auxins pathways during the first 72 h post-inoculation. Results obtained suggest a key role for genes involved in the oxidative burst and the lignin pathways in the initial sugarcane defense against the S. scitamineum infection.

A new role for the plant growth-promoting nitrogen-fixing endophytic bacteria Gluconacetobacter diazotrophicus has been identified and characterized while it is involved in the sugarcane-Xanthomonas albilineans pathogenic interactions. Living G.diazotrophicus possess and/or produce elicitor molecules which activate the sugarcane defense response resulting in the plant resistance to X. albilineans, in this particular case controlling the pathogen transmission to emerging agamic shoots. A total of 47 differentially expressed transcript derived fragments (TDFs) were identified by cDNA-AFLP. Transcripts showed significant homologies to genes of the ethylene signaling pathway (26%), proteins regulates by auxins (9%), beta-1,3 Glucanase proteins (6%) and ubiquitin genes (4%), all major signaling mechanisms. Results point toward a form of induction of systemic resistance in sugarcane-G. diazotrophicus interactions which protect the plant against X. albilineans attack.

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