Specific and Sensitive Detection of Venturia nashicola, the Scab Fungus of Asian Pears, by Nested PCR.

The fungus Venturia nashicola is the causal agent of scab on Asian pears. For the rapid and reliable identification as well as sensitive detection of V. nashicola, a PCR-based technique was developed. DNA fingerprints of three closely related species, V. nashicola, V. pirina, and V. inaequalis, were obtained by random amplified polymorphic DNA (RAPD) analysis. Two RAPD markers specific to V. nashicola were identified by PCR, after which two pairs of sequence characterized amplified region (SCAR) primers were designed from the nucleotide sequences of the markers. The SCAR primer pairs, designated as D12F/D12R and E11F/E11R, amplified 535-bp and 525-bp DNA fragments, respectively, only from genomic DNA of V. nashicola. The specificity of the primer sets was tested on strains representing three species of Venturia and 20 fungal plant pathogens. The nested PCR primer pair specific to V. nashicola was developed based on the sequence of the species-specific 525-bp DNA fragment amplified by primer set E11F/E11R. The internal primer pair Na11F/Na11R amplified a 235-bp fragment from V. nashicola, but not from any other fungal species tested. The nested PCR assay was sensitive enough to detect the specific fragment in 50 fg of V. nashicola DNA.

Polaribacter gangjinensis sp. nov., isolated from seawater.

A strictly aerobic, orange-pigmented and Gram-staining-negative bacterium, designated K17-16(T), was isolated from seawater of Gangjin Bay, Korea. Comparative 16S rRNA gene sequence analysis revealed that strain K17-16(T) was a member of the genus Polaribacter in the family Flavobacteriaceae and showed 94.0-95.6 % sequence similarity with the type strains of recognized species of the genus Polaribacter. The G+C content of the genomic DNA was 34.6 mol% and the major respiratory lipoquinone was MK-6. The major polar lipids detected were phosphatidylethanolamine, three unidentified amino-group-containing lipids and an unidentified aminophospholipid. The predominant cellular fatty acids were iso-C(15 : 0) (15.4 %), C(15 : 0) (12.4 %), summed feature 3 (comprising iso-C(15 : 0) 2-OH and/or C(16 : 1)ω7c; 10.6 %), C(15 : 1)ω6c (9.8 %) and iso-C(15 : 0) 3-OH (8.6 %). On the basis of phenotypic and genotypic data, strain K17-16(T) represents a novel species in the genus Polaribacter, for which the name Polaribacter gangjinensis sp. nov. is proposed. The type strain is K17-16(T) ( = KCTC 22729(T) = JCM 16152(T)).