Figure 5
Pathogenicity of M. oryzae ssd1 mutant on the third leaves of BSMV:HvCEBiP-treated barley plants. (A) Disease symptom index on barley leaves inoculated with M. oryzae: Type I, no visible disease symptoms; Type II, brown necrotic flecks; Type III, severe blast lesion with less brown necrotic flecks. (B) Quantification of disease symptoms at 7 dpi according to the disease index shown in (A). Conidial suspensions (1 × 105 conidia/ml) of the wild-type strain Hoku-1 or mossd1 mutant K4 were spotted onto the third leaves of BSMV- or BSMV:HvCEBiP-treated plants. Mutant K4 produced a greater frequency of Type II and Type III infections on BSMV:HvCEBiP-treated plants than on BSMV-treated plants. on BSMV:HvCEBiP-treated plants, the wild-type Hoku-1 also produced slightly more severe symptoms (type III) than on BSMV-treated plants. Twenty droplet inoculations were performed in each experiment with three biological replicates. Data represent mean numbers of inoculation sites and error bars = 1 standard deviation. (C) Cytology of appressorium-mediated infection by ssd1 mutant K4 on leaves of BSMV:HvCEBiP-treated plants. In Type II lesions, infection hyphae emerging from appressoria were observed inside only one epidermal cell, without further hyphal growth into adjacent cells. Formation of infection hyphae was associated with death of the penetrated cell. In Type III lesionsssss, infection hyphae developed further, colonizing neighboring cells, without visible host cell death. Ap, appressorium; Ih, infection hypha; Bar = 10 μm.