A loop-mediated isothermal amplification (LAMP) assay to detect the causal organism of huanglongbing (citrus greening) was developed. Primers were designed from the nucleotide sequence of the rpl KJAL-rpo B operon of Candidatus Liberibacter asiaticus. DNA amplification was greatly accelerated when loop primers were added to the reaction, and the reaction kinetics was correlated with the reaction temperature from 61°C to 65°C. Sodium hydroxide was used in a rapid DNA extraction method (called alkali extraction) that does not require maceration of leaves, and specific amplifications in the LAMP reaction were obtained from all samples prepared from Ca. L. asiaticus-infected plants. With these methods, Ca. L. asiaticus was detected when one infected leaf was mixed with four healthy ones. The threshold times for turbidity were equal to those for samples prepared from the same leaves using commercially produced regents.
Brown leaf spots and shoot blight were observed on perilla (Perilla ocymoides L.) in Osaka Prefecture in June 2006. The causal agent was identified as Colletotrichum destructivum O’Gara. The same symptoms were produced after inoculating perilla plants with present isolate. This report is the first of anthracnose of perilla in Japan. This pathogen, originally found on a reddish purple cultivar of perilla (akajiso), also infects P. frutescens (L.).
The rice blast fungus, Pyricularia grisea, was isolated from all diseased spikelets within a single panicle collected from a paddy fields in Hoya and a field in Terada in the Shonai district of Yamagata Prefecture, and the genotypes were identified using pot2 rep-PCR fingerprinting. Among the 300 monoconidial blast isolates were obtained from each panicle. Four and six genotypes were detected at Hoya and Terada, respectively. The isolates with the predominant genotypes were widely distributed in both panicles.
A new disease of edible burdock (Arctium lappa L.) was observed in Okayama Prefecture in 2002. The fungus consistently isolated from symptomatic roots was identified as Phoma exigua Desm. var. exigua on the basis of morphological characteristics of the fungus, color reaction with 1 N-NaOH on malt agar and pathogenicity on roots of edible burdock. Phoma black spot (Ne kokuhan-byo in Japanese) of edible burdock (Arctium lappa L.) is proposed for the new disease name.
Peduncle dieback following berry drop in the middle of grape clusters, primarily on cultivars Pione, Muscat Bailey A and Muscat of Alexandria, has been observed frequently at harvest time in Kagawa prefecture since 1999. On the basis of morphological and cultural characteristics and molecular phylogenies, the causal pathogens were identified as Diaporthe melonis var. brevistylospora and Phomopsis sp. Berry drop (Datsuryu-byou in Japanese) is proposed for the name of the disease. Both isolates caused grape berry drops and were also pathogenic to fruits of kiwifruit, satsuma mandarin and apple.