The effects of hydroxyl radicals (OH radicals) generated in a solution of hydrogen peroxide, oxalic acid and iron (III) under natural sunlight (“photo-Fenton reaction”) was tested against strawberry powdery mildew [Sphaerotheca aphanis (Wallroth) Braun var. aphanis]. Applications of the OH-radical-generating solution to whole plants before inoculation with a conidial suspension protected plants against the disease. The solution also had a suppressive effect for plants already diseased. Conidial germination was suppressed within 20 min of exposure of the solution in sunlight. These results suggested that OH radicals generated by the photo-Fenton reaction ultimately protected against new disease and suppressed further disease development.
Isolates of Colletotrichum gloeosporioides (Glomerella cingulata), obtained from strawberry leaves with anthracnose in Saga Prefecture in 2003, were bioassayed for sensitivity to strobilurin fungicides (azoxystrobin and kresoxim-methyl). The two isolates had little sensitivity to these fungicides, and they were regarded as resistant. Sequence analysis showed that the deduced amino acid at codon 143 of the mitochondrial cytochrome b gene was altered from glycine (GGT) to alanine (GCT). Polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) using the restriction enzyme ItaI could be employed in practice for rapid testing of resistance to strobilurin fungicides.
A new leaf spot disease of sugarcane (Saccharum officinarum L.) was found in Tokunoshima, Kagoshima Prefecture, Japan in June 2005. Reddish-brown and spindle-shaped lesions formed on the leaves of mericlone seedlings grown in the glasshouse. The causal fungus was exclusively isolated from the lesions, and typical symptoms were reproduced after inoculation with the isolate. The causal fungus was identified morphologically and phylogenetically as Curvularia lunata (Wakker) Boedijn. Hyphae grew at 10-38°C with optimum growth at 30°C. The name leaf spot of sugarcane, in Japanese “Hanten-byo”, is proposed for the disease.