Screening of sugarcane germplasm against Sporisorium scitamineum and its effects on setts germination and tillering.

Sugarcane smut is the most damaging disease that is present almost across the globe, causing mild to severe yield losses depending upon the cultivar types, pathogen races and climatic conditions. Cultivation of smut-resistant cultivars is the most feasible and economical option to mitigate its damages. Previous investigations revealed that there is a scarcity of information on early detection and effective strategies to suppress etiological agents of smut disease due to the characteristics overlapping within species complexes. In this study, 104 sugarcane cultivars were screened by artificial inoculation with homogenate of all possible pathogen races of Sporisorium scitamineum during two consecutive growing seasons. The logistic smut growth pattern and the disease intrinsic rate were recorded by disease growth curve. Variable levels of disease incidence i.e., ranging from 0 to 54.10% were observed among these sugarcane cultivars. Besides, pathogen DNA in plant shoots of all the cultivars was successfully amplified by PCR method using smut-specific primers except 26 cultivars which showed an immune reaction in the field trial. Furthermore, the plant germination and tillering of susceptible sugarcane cultivars were greatly influenced by pathogen inoculation. In susceptible cultivars, S. scitamineum caused a significant reduction in setts germination, coupled with profuse tillering, resulting in fewer millable canes. Correlation analysis demonstrated that there was a positive relationship between reduction in setts germination and increase in the number of tillers. The present study would be helpful for the evaluation of smut resistance in a wide range of sugarcane germplasm, especially from the aspects of setts germination and tillers formation, and it also screened out several excellent germplasm for potential application in sugarcane breeding.

Impact of Sporisorium scitamineum infection on the qualitative traits of commercial cultivars and advanced lines of sugarcane.

Whip smut disease of sugarcane, caused by Sporisorium scitamineum, is considered one of the main constraints in the successful cultivation of sugarcane. The pathogen infection can decrease the quantity and quality of the produce. Cultivation of resistant varieties is the most feasible strategy to combat the harms of this devastating disease. Development of varieties having disease-resistance together with improved important traits such as brix, pol, purity, CSS, and low fiber contents are desirable. Therefore, we documented the variances in quality traits of 104 sugarcane cultivars under disease pressure in split-plot design with 6 replications. The split ANOVA revealed a highly significant impact (p<0.0001) between treatments (inoculated and uninoculated), within cultivars as well as interaction 'Cultivars x Treatments' effect on brix, pol, fiber, purity, and CSS contents. In inoculated plots, the infection of S. scitamineum brought a highly significant reduction (t>4.032) in brix, pol, purity, and CSS of more than 40% of the cultivars used, as compared to the uninoculated ones. On the other hand, the smut infection caused a highly significant (t>4.032) increase in fiber percentage of 41 cultivars. We found significant positive correlations between smut rating and reduction of brix, pol, purity, and CSS contents. The cultivars that were caught with greater disease severity, compromised a higher reduction of their useful contents. Similarly, a significant positive correlation was found between increased fiber percent and smut rating. Remarkably, cultivars that showed immune reactions to whip smut disease were not statistically different from uninoculated ones in brix, pol, purity, CSS, and fiber contents. Variable effects of whip smut infection to quality parameters of different cultivars depict the importance of further improvement through breeding programs.