Exploring the Role of Cuticular Wax in Resistance to Bacterial Leaf Blight in Rice through Morphological, Metabolomic, and Gene Expression Analyses

Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv oryzae ( Xoo ), is a major constraint to rice productivity worldwide. This study investigated cuticular wax as a physical and biochemical barrier associated with BLB resistance using eight contrasting genotypes (two each from the resistant, moderately resistant, susceptible, and highly susceptible groups). The resistant genotypes showed higher wax content (2.7–3.5 μg cm –2 ), along with greater surface hydrophobicity (contact angle >100°), and dense wax crystal deposition. Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) revealed clustering of genotypes based on wax metabolite profiles. Orthogonal partial least squares (OPLS) indicated a strong correlation between wax composition and BLB response. Heptadecane and octacosane were key resistant genotypes associated wax metabolites. RT-qPCR showed upregulation of cuticular wax biosynthesis pathway genes ( OsCER1 and OsWSL2 ) in resistant genotypes. These results highlight wax content and composition as targets for developing disease-resilient rice cultivars.