Identification and pathogenicity study of emerging fish pathogens Acinetobacter junii and Acinetobacter pittii recovered from a disease outbreak in Labeo catla (Hamilton, 1822) and Hypophthalmichthys molitrix (Valenciennes, 1844) of freshwater wetland in West Bengal,India

The disease outbreaks in aquaculture system of wetlands are the major cause of fish mortality. Among various bacterial septicaemic diseases, fish mortality caused by Acinetobacter spp. is recently reported in different fish species. Fish disease outbreak was investigated in a wetland of West Bengal, India to identify the aetiological factors involved. The moribund fish were examined and subjected to bacterial isolation. Two bacterial causative agents were identified as Acinetobacter junii and Acinetobacter pittii by biochemical characterization and 16S rRNA gene amplification. Both the isolates were oxidase‐negative, nitrate‐negative, catalase‐positive and indole‐negative. The molecular identification using 16S rRNA gene sequencing and phylogenetic tree analysis further confirmed the two Acinetobacter spp. with 97%–99% similarity. The antibiotic resistance patterns of these two bacteria revealed that both of them were resistant to β‐lactam, cefalexin, cephalothin, amoxyclav, cefuroxime, cefadroxil, clindamycin, vancomycin and penicillin. In addition, A. pittii was also resistant to other antibiotics of cephams group such as ceftazidime and cefotaxime. In the challenge experiment, both A. junii and A. pittii were found to be pathogenic with LD₅₀ of 1.24 × 10⁵ and 1.88 × 10⁷ cfu/fish respectively. Histopathological examination of gill, liver and kidney revealed prominent changes supporting bacterial septicaemia. The investigation reports for the first time on concurrent infection by A. junii and multidrug‐resistant (MDR)‐A. pittii as emerging fish pathogens to cause severe mortality in Labeo catla and Hypophthalmichthys molitrix in a freshwater wetland.     

Analysis of genetic diversity and discrimination of Oil Palm DxP populations based on the origins of pisifera elite parents

A total of 251 Dura cross Pisifera (DxP) hybrid palms from six populations descending from six parental African Pisifera origins and involving 12 progenies were analyzed with 19 selected Simple Sequence Repeats (SSR) markers. A total of 110 alleles were produced, ranging from three to eight per SSR, with a mean of 5.8 alleles per SSR locus. Of these, 68.5% were considered shared alleles by more than one population and the remaining 31.5% were population specific alleles. They generated between six and 21 haplotypes in all populations, and depending on the SSR marker, between one and 10 haplotypes within populations. Various parameters for analyzing genetic variability, differentiation and genetic structure were computed using GenAlEx, Structure and Darwin software. The obtained results confirmed microsatellites as a robust, feasible and trustful method for obtaining DNA fingerprints, tracing the source of oil palm samples. With respect to the authenticity of materials or for solving legitimacy issues, accession belonging to each population by SSR markers could be distinguished, but additional SSR should be screened for improving this process.     

Nested PCR assay for detection of sugarcane grassy shoot phytoplasma in the leafhopper vector Deltocephalus vulgaris: a first report

Nymphs of Deltocephalus vulgaris , the leafhopper vector of sugarcane grassy shoot (SCGS) disease, fed on SCGS-infected and healthy sugarcane leaves, and SCGS-infected and healthy plant tissue of sugarcane cv. CoLk 8102, were examined by nested PCR using phytoplasma-specific rRNA operon primers for detection of the SCGS phytoplasma. Samples of SCGS-infected plants with symptoms and SCGS-exposed D. vulgaris nymphs yielded SCGS-exclusive DNA bands when nested PCR was performed. Negative results were obtained when symptomless plant host and unexposed insect vector samples devoid of phytoplasma DNA templates were used. Such a reliable molecular tool for the precise detection of SCGS phytoplasma in the D. vulgaris population would help forecast the potential of secondary spread of SCGS in a susceptible sugarcane variety, and may facilitate control of the disease.     

Spatio-temporal analysis of cyprinid herpesvirus 3 genetic diversity at a local scale

Cyprinid herpesvirus 3 (CyHV-3), the causative agent of koi herpesvirus disease, is a major threat for carp populations in many countries worldwide, including Indonesia. It has been shown that many genotypes circulate worldwide, all highly related to one of the two known lineages U/I and J. In this study, we evaluated the spatial and temporal distribution of CyHV-3 strains in a small enzootic area, the lake of Cirata (West Java, Indonesia). Of the 365 samples analysed, from clinical or asymptomatic fish, 244 were found positive for CyHV-3, suggesting a high occurrence of the virus. Genotyping of these viral specimens with a range of molecular markers revealed the presence of numerous haplotypes in the host population, all related to the J lineage. In single individuals, mixed-genotype infections occurred at high frequency. The present results demonstrate that polymorphic molecular markers are suitable to monitor the genetic evolution of a viral population in an enzootic area.