Evaluation of two forms of Sporisorium scitaminea sydow inoculum in sugarcane

Smut, caused by Sporisorium scitaminea Sydow, is one of the main destructive diseases in sugarcane (Saccharum spp.). To assess the resistance of sugarcane to smut, two different isolates of S. scitaminea were inoculated to sugarcane plants by means of pin-prick dipping in nodal buds. Data on the disease latent period and disease incidents per population were recorded and analyzed. Results showed the inoculum used in the present study was the S. scitaminea race 2 according to the resistance levels of standard control varieties F134 and NCo310. While the variety NCo376 used to be immune to smut became susceptible, inferring the pathogenicity of S. scitaminea in our study was stronger than that reported previously, or it had generated virulence mutations. The “+” and “-” mating type sporidia mixture (1:1) as inoculum gave better results than teliospores suspension inoculation, indicating the sporidia suspension by pin-prick dipping inoculation is more appropriate for identifying primary sources of resistance. Six sugarcane clones (GT36, GT37, YT93-159, GXS85-30, GXS145 and GXS222) were found to have higher levels of resistance to smut than others, so they could be useful resources to improve smut resistance in sugarcane breeding.