The 16S rRNA gene sequences for 34 strains, including 11 isolates, were determined to classify scab-causing Streptomyces spp. and relatives isolated from potato scab lesions collected in Jeju, Korea. The 16S-23S rDNA internally transcribed spacer (ITS) sequences were determined to investigate whether the 16S-23S ITS region is useful for analysing intra-and interspecific relationships in these bacteria. On the basis of phylogenetic analysis of 16S rRNA gene sequences, most of the isolates were classified as Streptomyces scabiei and Streptomyces acidiscabies. Isolate KJO61 was placed in an ambiguous taxonomic position between Streptomyces reticuliscabiei and Streptomyces turgidiscabies. 16S-23S ITS region sequence analysis showed that tRNA genes were not found in this region of Streptomyces spp. The 16S-23S ITS regions of Streptomyces spp. exhibited various lengths and highly variable sequence similarities (35-100 %) within strains as well as intra-and interspecies. It was revealed that Streptomyces europaeiscabiei could be clearly differentiated from Streptomyces scabiei. However, it was clarified that ITS regions are not useful in phylogenetic analysis of Streptomyces spp.

Citrus is the most extensively produced fruit tree crop in the world and is grown in over 130 countries. Fungal diseases in citrus can cause significant losses in yield and quality. An accurate diagnosis is critical for determining the best management practices and preventing future losses. In this study, a Recombinase polymerase amplification (RPA)-clustered regularly interspaced short palindromic repeats (CRISPR)/associated (Cas) system was established with the integration of a lateral flow assay (LFA) readout system for diagnosis of citrus scab. This detection can be completed within 1 h, is highly sensitive and prevents cross-reactions with other common fungal citrus diseases. Furthermore, the detection system is compatible with crude DNA extracted from infected plant tissue. This RPA-CRISPR/Cas12a-LFA system provides a sensitive, rapid, and cost-effective method with promising and significant practical value for point-of-care diagnosis of citrus scab. To our knowledge, this is the first report to establish an RPA- and CRISPR-based method with LFA for fungal diseases in plants.

No abstract

Acidovorax citrulli, the causal agent of bacterial fruit blotch, has caused an economically destructive damage in cucurbits cultivation fields worldwide. To consider more effective disease management, 33 A. citrulli isolates collected from various cucurbits in Korea were analysed by multi-locus phylogeny using five conserved loci (16S rRNA, adk, gltA, glyA, pilT). Two distinct groups (KCC1 and KCC2) in the population were identified on the base of group-specific genetic variation. Out of them, the predominant group was KCC2 and both groups included isolates from melon, cucumber and watermelon. Sixty-four percent of KCC1 isolates were recovered from non-watermelon hosts and seventy-two percent of KCC2 isolates from watermelon. This study presented that there was genetic differentiation among A. citrulli population in Korea. Also, these results will be applied as a very useful data in effective disease management.

Pink mold rot of tomato occurred very severly on tomato farm in Paju, Gyounggi Province, Korea, in July 2005. The infected fruits were dropped and abandoned and the symptoms were similar to calcium deficient tomatoes. But symptom was a slight water-soaked area on or near the blossom end of the fruit and firm greyish-brown lesions were most found at the blossom-end of affected fruits. lesions caused by the pink mold fungus possess a water soaked margin and rise to characteristic orange-pink spores. Also when the diseased tomato was cut, the inside of tomatoes showed completely rotted with pink mold. The causal fungus was identified as Trichothecium roseum based on mycological characteristics. This is the first report of T. roseum infecting greenhouse tomatoes in Korea.