Characterization of sugarcane response to Bipolaris sacchari : inoculations and host-specific HS-toxin

Twenty-seven sugarcane clones inoculated with Bipolaris sacchari, causal agent of eyespot disease, were classified as susceptible or resistant based on the presence or absence of distinct chlorotic halos surrounding lesions on leaves. Under the inoculation conditions used in this study, all lesions on resistant plants were smaller than 3 mm; the proportion of lesions larger than 3 mm on susceptible clones ranged from 0.2 to 82.2%. The total number of lesions was not related to resistance or susceptibility. All clones classified as resistant to B. sacchari were insensitive to a host-specific toxin (HS-toxin) produced by the pathogen, whereas all susceptible plants produced a water-soaked streak when 1 yl of partially purified HS-toxin was placed in a hole punched in a leaf segment [...]