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The effects of increasing yield and quality of virus-free chewing cane seedlings and their physiological and molecular basis were studied in this study. Results showed that compared with infected seedlings (the control), the yield of chewing cane stems grown from virus-free seedlings increased by 21.81–29.93%, stem length increased by 28.66–34.49 cm, internode length increased by 2.16–2.68 cm, the single stem weight increased by 20.10–27.68%, the reducing sugar increased by 0.91–1.15% (absolute value), and sucrose increased by − 0.06–1.33% (absolute value). The decrease in sucrose content did not reach significant level, but all other parameters were reached significant level. The chlorophyll content, photosynthetic parameters such as stomatal conductance (Gs), net photosynthetic rate (Pn) and transpiration rate (Tr), the activity of photosynthetic key enzymes ribulose-1,5-bisphosphate carboxylase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC), and gene ( pepc , rbcS, and rbcL ) expression levels were all greater in virus-free seedlings than infected seedlings. The content of superoxide anion (O 2 − ) and malondialdehyde (MDA) in virus-free seedlings was lower than infected seedlings at the main growth stage. With increased development, the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were gradually higher in virus-free seedlings than infected seedlings. Our results indicate that virus-free seedlings may improve photosynthesis efficiency and promote photosynthesis by increasing chlorophyll content, photosynthetic key enzyme activity, and the gene expression levels in leaves. By increasing the activity of antioxidant enzymes, reducing the degree of membrane lipid peroxidation, and improving the stress resistance of chewing cane, the virus-free chewing cane seedlings increased yield and quality. Our findings provide a scientific and theoretical basis for the promotion and application of virus-free chewing cane seedlings.

Sugarcane smut is a fungal disease caused by Sporisorium scitamineum. To explore its biological control strategies, this study collected rhizosphere soil of sugarcane, isolated and identified biocontrol bacteria from it, and conducted multi-level control efficacy evaluations. The results showed that five bacterial strains with effective antagonistic activity against the sexual mating and teliospore germination of S. scitamineum were isolated and identified: 2143-2 (Pseudomonas baetica), 2143-4 (Bacillus subtilis), 2143-6 (Burkholderia diffusa), Y8-2 (Pseudomonas reinekei), and Y8-3 (Bacillus amyloliquefaciens). The results of the pot inoculation experiments showed that all five strains could prolong the incubation period of sugarcane smut and significantly reduce the disease incidence, demonstrating marked control effects, with strains 2143-4 and Y8-2 being the most effective. The results of the field inoculation experiments and natural field infection experiments indicated that strain Y8-2 exhibited the best biocontrol efficacy against sugarcane smut, with control efficacies of 68.40% and 73.99% in the field inoculation experiments, and 65.73% under natural field infection conditions. In addition, the biocontrol strains could improve the physiological stress-tolerance characteristics of sugarcane plants, which was conducive to enhancing the resistance of sugarcane plants to sugarcane smut.

The genetic relationships among 90 mating-type isolates of Sporisorium scitamineum collected from mainland China were evaluated based on the start codon-targeted (SCoT) marker technique. Fourteen selected SCoT primers amplified 135 DNA fragments, of which 98 (72.6 %) were polymorphic. The polymorphic information content values ranged from 0.649 to 0.910 with an average of 0.820, indicating that a high degree of genetic diversity exists among these Chinese S. scitamineum isolates. Cluster groups identified using the unweighted pair-group method with arithmetic mean (UPGMA) and principal component analysis (PCA) were similar and divided the 90 S. scitamineum isolates into three main groups (G1, G2, and G3) based on a Jaccard’s similarity coefficient of 0.74. The S. scitamineum isolates collected from the same province tended to cluster in the same main groups. This study showed that the genetic diversity of the 90 S. scitamineum isolates was associated with their geographic origin, with no evidence of coevolution between the host and S. scitamineum. The knowledge of genetic diversity of S. scitamineum is useful in breeding programs for development of smut-resistant sugarcane genotypes. The results of this study demonstrate that SCoT markers are informative and can be used to evaluate the genetic diversity of S. scitamineum.