Optimising sporulation and virulence in Drechslera avenacea

Studies were conducted on agar media to optimise sporulation of Drechslera avenacea, a fungal pathogen being evaluated as a biological control agent for Avena species (wild oats). Conidium production was affected by nutrition, pH, temperature and light conditions. Of the agar media tested, Czapek Dox agar (CZA) and half-strength oatmeal agar (OMA) were the only media where sporulation occurred at all temperatures tested under a 12-h light:12-h dark photoperiod (L/D). The optimum temperature for conidium production was 20°C on OMA, whereas there was no optimum temperature on CZA. Under a 12-h near-ultraviolet (NUV):12-h dark photoperiod (NUV/D), similar numbers of conidia were produced on CZA at 6.66, 14.56, and 22.78 W m-2, whereas on OMA conidium production was the highest at 14.56 W m-2. When NUV/D and L/D conditions were compared, similar numbers of conidia where produced on CZA, whereas OMA conidium production was superior under the NUV/D photoperiod. Considerable variation in sporulation and degree of violence of D. avenacea was detected among isolates from different geographic areas. The most virulent conidia were obtained on OMA at 20°C incubated under continuous illumination NUV light. Therefore, the most suitable conditions for conidium production of D. avenacea were growth for 1 week on OMA at 20°C under continuous NUV at an intensity of 14.56 W m-2. Under these conditions, 1.1×105 conidia mL-1 were produced which is the highest sporulation yet reported for any Drechslera spp., which are traditionally poor sporulators

Characterization of culturable bacterial community associated with Thunnus tonggol (longtail tuna) and Caranx sem (blacktip trevally) marketed in the fish market of Muscat (Oman)

The present study was conducted to evaluate the freshness of two Omani fishes; Thunnus tonggol (Longtail Tuna) and Caranx sem (Blacktip trevally), marketed in the fish market of Muscat, through the characterization of the bacterial community as an indicator for fish quality. Therefore, 15 fishes from each type were collected from Muscat fish market during the period between September 2019 and October 2021. Skin surface of the fish was examined. Ten grams of each fish were cut from skin surface under aseptic conditions. The cut samples were homogenized and diluted in sterile water. Samples were then cultivated and identified by routine biochemical identification tests and confirmed by the identification system EPI20E when appropriate. A total of 13 bacterial species were detected including A. hydrophila, A. salmonicida, C. freundii, E. piscicida, E. tarda, H. alvei, L. garvieae, S. marcescens, Y. ruckeri, E. coli, K. pneumonia, P. aeruginosa and S. aureus. Among the thirteen bacterial specie, A. hydrophila, A. salmonicida, Y. ruckeri, E. coli, K. pneumonia, P. aeruginosa and S. aureus were found to be common in all collected samples.&nbsp