Field assessment and combining ability analysis for smut resistance in sugarcane during continuous ratoon planting in China

Sugarcane smut, caused by Sporisorium scitamineum, poses a significant threat to sugarcane production in China, resulting in substantial economic losses. This study aims to understand the resistance of sugarcane genotypes to smut and the relationship between smut incidence and yield loss during ratoon cropping. We evaluated the smut resistance of 169 sugarcane genotypes. We assessed the combining ability of nine female and six male parent plants in field trials conducted from 2019 to 2022 in Fusui or Longzhou, China. Our findings reveal increased smut incidence with each successive ratoon cycle, particularly after the second ratoon. Smut infection during the ratoon cycle reduced sugarcane yield by decreasing the number of millable stalks. Variance analysis indicated that genotype, cropping cycle, and location significantly influenced disease incidence. Based on resistance levels, the genotypes were categorized into five groups: 10 highly resistant, 37 resistant, 38 moderately susceptible, 42 susceptible, and 42 highly susceptible. Analysis of general combining ability (GCA) and specific combining ability (SCA) demonstrated that crossing sugarcane parents with smut resistance effectively produced resistant hybrid offspring. Additionally, the maternal inheritance effect was more pronounced than the paternal inheritance effect, indicating that using a resistant genotype as the maternal parent is more advantageous for enhancing smut resistance. These results provide valuable insights into sugarcane smut resistance, aiding in selecting parental lines and breeding new resistant varieties.