Morphological and Phylogenetic Characterization of Whip Smut on Commercial Sugarcane Cultivars and Assessing the Resistance to Sporisorium scitamineum

Abstract

Whip smut, which is caused by Sporisorium scitamineum, is an important disease in areas where sugarcane is cultivated in Iran, particularly in the Khuzestan province. The pathogen significantly reduces sugarcane yield, and the use of resistant cultivars is the most cost-effective strategy for managing the disease. The present study characterized the S. scitamineum strains collected from five commercial sugarcane cultivars (CP69-1062, CP57-614, CP48-103, SP70-1143, and NCo310) based on their morphological and phylogenetic features. The sporidial cultures of the strains appeared in two growth forms: cottony colony and yeast-like. All strains were found to be identical based on the DNA sequences of ITS, COX3, GAPDH, and EF1α regions, and revealed that all strains were identical (100%) to the reference strain of S. scitamineum. The disease incidence of the cultivars varied from 5 to 43% during two consecutive years. Statistical analysis of the growth rates of the strains indicated significant differences. Combined analysis of variance (ANOVA) suggested that the effects of year, strain, cultivar, and the interaction effect of strain ´ cultivar were significant at a 1% probability level. Our results suggest that IRK310 was the most virulent among all cultivars, with different pathogenicity percentages, while the strain IRK70 had the lowest level of virulence among all strains. Among the tested cultivars, SP70-1143 and CP57-614 showed high resistance to smut. In this research, teliospore populations of whip smut were identified, and disease reactions of the cultivars were assayed. Screening and selecting smut-resistant cultivars can help reduce disease damage in cultivated areas and can serve as a basis for further research on plant disease management.

Keywords

• disease management
• genetic diversity
• housekeeping genes
• whip smut