EXPRESSION PROFILING OF SUGARCANE GENOTYPES CONTRASTING FOR DROUGHT TOLERANCE

The Brazilian sugarcane industry is expanding rapidly, particularly to drought-prone regions. We characterized tolerance by phenotyping and attempted to identify genes with roles in drought tolerance. From 100 genotypes, 10 were selected and evaluated for drought tolerance in a field trial in Goianésia and under greenhouse conditions. Based on morphophysiological evaluations, we identified two contrasting genotypes for response to drought stress: ‘IACSP94-2094’ showed enhanced features of drought tolerance (early stomatal closure; maintenance of leaf water potential; and superior photochemical activity), absent in ‘IACSP97-7065’. Leaf samples collected from these contrasting genotypes under irrigation or drought conditions in a field trial at two moments (early and after severe drought) were used to perform microarray analysis. From a set of 14,522 genes, 91 were differentially expressed between irrigated or non-irrigated treatments during early drought, whereas 576 were differentially expressed during severe drought between water treatments, from which 438 were differentially expressed between genotypes. ‘IACSP94-2094’ showed more changes in expression than ‘IACSP97-7065’ in genes from pathways associated with drought tolerance, such as oxidation/reduction, hormone metabolism, response to stress, and response to abiotic stimulus by gene ontology analysis. Leaf samples from the same genotypes grown in the greenhouse under similar treatments were used for gene expression profiling by RNAseq. Using the sugarcane assembled sequences as reference (43,141 genes), we identified 2,300 as differentially expressed. Most of the genes identified by microarrays were also observed in RNAseq, with similar expression levels. Target genes are being used for functional genomics assays to develop new drought-tolerant cultivars.