Alternaria black spot

The Alternaria black spot fungi A. brassicae and A. brassicicola produce host-selective toxins as well. While A. brassicicola produces brassicicolin A (11) as the major host-selective phytotoxin [28], A. brassicae produces destruxin B (12) (Fig. 9.4) [29]. Consistent with the virulence of these phytopathogens, both brassicicolin A (11) and destruxin B (12) appeared to be more phytotoxic to the susceptible cruciferous species B.juncea than to the tolerant B. napus. 

The toxins of many members of the fungal genus Al-ternaria produce phytotoxins of these, many [such as AM-toxin I (18)] are peptides. The fungal pathogen Alternaria mali on apples produce necrotic lesions on the leaves, shoots, and fruits of susceptible cultivars (Natori et al, 1981). Alternaria kikuchiana, which causes black spot disease on the Japanese pear (Pyrus serotina) produces phytotoxins which are based on A -acetylphenylalanine and a Cio fatty acid (Harbome, 1986). 

Fruit with spots flesh may rot. Causes Angular leaf spot Alternaria blight black rot scab other fungal or bacterial diseases. See "Leaves with spots, blotches, or brown areas on page 85 for controls. 

Macroscopic Appearance A rapidly growing rich gray black to blackish mycelium. Alternaria first appears as scattered blackish spots in the spawn jars, soon spreading and overwhelming The mushroom mycelium. On agar, it resembles a black Penicillium- ke mold. 

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