In 2003 and 2004 years, brown spot symptoms were observed on tea leaves in tea fields in Kagoshima prefecture, mainly after typhoons. A severe incidence caused leaf fall and bud blight. A bacterium that formed a white, circular colony on King's B medium, was always isolated from lesions, and leaf symptoms of tea were reproduced after inoculation with this bacterium. Based on its bacteriological characteristics, pathogenicity on tea leaves and a 16S rRNA sequence analysis, the bacterium was identified as Acidovorax valerianellae Gardan, Stead, Dauga and Gillis 2003. This is the first report of bacterial spot of tea caused by Acidovorax valerianellae in Japan.
The causal phytoplasma of gentian witches'-broom, found in Iwate Prefecture in 2005, was identified phylogenetically as ‘Candidatus Phytoplasma asteris’, but not ‘Candidatus Phytoplasma pruni’, which was previously reported as the pathogen of gentian witches' broom in Japan. The causal phytoplasma was also revealed to be transmitted by Macrosteles striifrons. We propose adding ‘Candidatus Phytoplsma asteris’ to the pathogens of gentian witches'-broom.
We examined the priming effects of four plant defense activators (probenazole [PBZ], methyl jasmonate [MeJA], acibenzolar-S-methyl [ASM], and carpropamid [CRP]) in rice cells. Activators potentiated the elicitor-responsive expression of Cht-1 gene by 4-to 7-fold. MeJA greatly activated PBZ1 and Os PAL1 gene expression by over 50-fold, and CRP also enhanced PBZ1 gene expression to the same degree. On the other hand, activators accelerated the elicitor-responsive photon emission and augmented its peak intensity by 2- to 3-fold. These results indicated that each elicitor response was potentiated by plant defense activators in different but overlapping manners. Among elicitor responses, photon emission can be a useful marker for priming because of its sensitivity to various kinds of activators and a simple strategy for its estimation.
A black spot disease on flowering cabbage (Brassica oleracea L. var. acephala DC.) was found in Shizuoka Prefecture, Japan in March 2003. A fungus was isolated and used to inoculate cabbage leaves to reproduce the black spot symptoms. It was identified as Alternaria brassicicola. This is the first record of the disease in Japan and is named black spot (Kokuhan-byo) on flowering cabbage.