Abstract
Yellow spot of leaves of sorghum (Holcus sorghi var. japonicus, or Sorghum vulgare) was found in Chiba prefecture near Tokyo since 1940. The disease is characterised by chlorotic (yellow, but not necrotic) and rectangular spots with white powdery appearnce (conidial formation), especially on their under surface. Later, the spots will change into light brownish necrotic lesions without conspicuous border colorations.
Conidiophores extrude through stomata singly or in tuft of 2 to about twelve, geniculate then denticulate towards apex, 22-80×3.6-6.9μ and 0-5 septate. Conidia are obclavate with obconic then truncate bottom and attenuate then blunt apex, 21-55×3-6μ and 1-6 (mostly 3) septate.
There can not find no identical sorghum fungus, but sugar cane yellow spot fungus (Cercospora koepkei Krüger) is similar in many respects on the morphology. Therefore, the sorghum fungus is to be inferred as C. koepkei Krüger var. sorghi, var. nov. The difference in description has been given.
