Development of species-specific primers for detection of Xanthomonas campestris pv. campestris causing black rot of crucifers

Aim: Black rot of crucifers caused by Xanthomonas campestris pv. campestris (Pammel) Dowson (Xcc) is a major seed-borne disease. The present study aimed to develop a rapid diagnostic protocol for the specific and sensitive detection of this pathogen. Methodology: A specific primer set was designed based on rpf gene and optimization of PCR condition was done for specific detection of Xcc. Sensitivity of PCR for primer set was then determined by diluting the Xcc DNA and cells. Results: Specific primer set was able to amplify a specific band of 304 bp in all 11 isolates of Xcc but failed to amplify other Xanthomonas species and one each of Ralstonia solanacearum, Erwinia caratovora subsp. caratovora, Bacillus subtilis, Pseudomonas fluorescens and P. aeruginosa. The primer set was highly sensitive as it was able to detect 10 pg μl-1 bacterial DNA and up to 3x103 CFU ml-1 corresponding to 12 viable cells of Xcc which were used as template for PCR reaction Interpretation: The results suggest that developed PCR primers are highly specific and sensitive and it can be used to detect the pathogen at an early stage of infection for disease management.

Pathology of a H5N1, highly pathogenic avian influenza virus, in two Indian native chicken breeds and a synthetic broiler line.

In this study, susceptibility to H5N1 virus infection was studied in two Indian native chicken breeds viz. Kadaknath and Aseel (Peela) and an Indian synthetic broiler strain (Synthetic dam line (SDL-IC). Fifty birds from each genetic group were infected intra-nasally with 1000 EID50 of a highly pathogenic avian influenza virus (HPAIV) strain A/chicken/Navapur/India/7972/ 06 (H5N1) and observed for a period of 10 days. Significant differences in severity of clinical signs, gross lesions and time for onset of symptoms were observed. The overall severity of clinical signs and gross lesions was less in SDL-IC broilers as compared to the other two genetic groups. The mortality percentages were 100, 98 and 92% with Mean Death Time (MDT) of 3.12, 5.92 and 6.96 days, respectively for the two native breeds Kadaknath and Aseel (Peela), the and SDL-IC broiler strain. Comparison of histological lesions revealed differences in disease progression among the genetic groups. Vascular lesions such as disseminated intravascular coagulopathy (DIC) were predominant on 3 days post infection (dpi) in Kadaknath, and on 5 and 6 dpi in Aseel (Peela) and SDL-IC broiler. The mean log2 HA titres of the re-isolated virus from various organs of H5N1 AIV infected birds of the three genetic groups ranged from 2.32 (lung, trachea and bursa) to 5.04 (spleen) in Kadaknath; 2.32 (lung) to 6.68 (brain) in Aseel (Peela); and 2.06 (liver) to 7.01 (lungs and kidney) in SDL-IC broiler. These results suggest that the susceptibility to H5N1 highly pathogenic avian influenza virus infection differed among the three breeds; Kadaknath being highest followed by Aseel (Peela) and synthetic SDL-IC broiler.This is possibly the first report on the differences in the susceptibility of the India native breeds to H5N1 virus infection and its severity.

Antiviral activity of crude extracts of Eugenia jambolana Lam. against highly pathogenic avian influenza (H5N1) virus.

Crude extracts of leaves and bark of E. jambolana were tested for antiviral activity against highly pathogenic avian influenza virus (H5N1) by CPE reduction assay in three different layouts to elucidate virucidal, post-exposure and pre-exposure antiviral activity of the extracts. The cold and hot aqueous extracts of bark and hot aqueous extract of leaves of E. jambolana showed significant virucidal activity (100% inhibition) which was further confirmed in virus yield reduction assay (~98 to 99% reduction) and by egg based in ovo assay. The selective index (CC50/EC50) of hot aqueous extract (248) and cold aqueous extract (43.5) of bark of E. jambolana showed their antiviral potential against H5N1 virus. The significant virucidal activity of leaves and bark of E. jambolana merits further investigation as it may provide alternative antiviral agent for managing avian influenza infections in poultry farms and potential avian-human transmission.