Aims
To evaluate the antimicrobial activities of an active compound isolated from the culture broth of Amphirosellinia nigrospora JS‐1675 against various plant pathogenic bacteria and fungi.
Methods and Results
While screening for bioactive secondary metabolites from endophytic fungi, we found that A. nigrospora JS‐1675 showed strong in vitro antibacterial activity against Ralstonia solanacearum. One compound (1) was isolated and identified as (4S, 5S, 6S)‐5,6‐epoxy‐4‐hydroxy‐3‐methoxy‐5‐methyl‐cyclohex‐2‐en‐1‐one. Growth of most of the tested phytopathogenic bacteria was inhibited by compound 1 and the ethyl acetate (EtOAc) layer except Pseudomonas syringae pv. lachrymans. Compound 1 also inhibited the mycelial growth of several plant pathogenic fungi. Both compound 1 and the EtOAc layer reduced bacterial leaf spot disease in detached peach leaves. They also suppressed the development of bacterial wilt on tomato seedlings quite effectively.
Conclusions
Amphirosellinia nigrospora JS‐1675 showed antimicrobial activity against plant pathogenic bacteria and fungi by producing compound 1.
Significance and Impact of the Study
This is the first report on the occurrence of compound 1 in A. nigrospora JS‐1675 and its efficacy against plant pathogenic bacteria and fungi. Their strong disease control efficacy against tomato bacterial wilt suggests that this fungus can be used as a microbial bactericide.
An analysis of the 524 nucleotide long segment in the 16SrDNA mitochondrial gene of Maurolicus japonicus revealed that there are two major haplotypes (E and H) and two minor haplotypes (I and J), which comprise 63Á6, 27Á2, 4Á6 and 4Á6% of the population, respectively. The nucleotide sequence of the major haplotype E is identical to that of the most common haplotype in Maurolicus walvisensis (63Á6% of the population). The other haplotypes of M. japonicus are almost identical to that of the haplotype E with only a single (haplotypes I and J) or three nucleotide differences (haplotype H). Phylogenetic trees of all the 16SrDNA haplotypes found thus far in the Maurolicus taxa show that the relationships among the haplotypes of M. japonicus and M. walvisensis are indistinguishable but that they are clearly distinctive from those of Maurolicus muelleri. Examination of the morphometric characteristics of specimens reveals similarities among the individuals of different haplotypes of M. japonicus and also between M. japonicus and M. walvisensis in almost all characteristics. The results suggest that despite the current ocean-wide allopatric distribution between M. japonicus and M. walvisensis, the two taxa are conspecific as M. japonicus.
ABSTRACT.Odontobutis obscura is a bottom-dwelling freshwater fish native to East Asia. Its range encompasses southwest China, western Japan, and Geoje Island in South Korea. Despite its widespread range in China and Japan, only a small and spatially isolated population is found in South Korea. We developed a total of 23 novel and polymorphic microsatellite loci of O. obscura using Illumina paired-end shotgun sequencing and characterized them using 80 Japanese and Korean samples. An extensive genetic polymorphism was detected at these 23 loci, with the observed number of alleles at a locus ranging from 2 to 15 and expected and observed heterozygosities ranging from 0 to 0.656 and 0 to 0.547, respectively. Korean O. obscura exhibited a much lower level of genetic variability than the Japanese population did, probably as a result of long-term isolation combined with historical bottlenecks. The Japanese and Korean populations showed a high level of genetic differentiation with F ST = 0.700 and R ST = 0.913. Many of our primer sets were successfully transferable to congeneric O. interrupta and O. platycephala, which exhibited even greater polymorphism than Korean O. obscura. In conclusion, our study showed that these 23 microsatellite markers are useful for understanding the conservation biology and population genetic structure of O. obscura and other congeneric species.
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