Molecular characterization and pathogenicity of Pythium species associated with damping-off in greenhouse cucumber (Cucumis sativus) in Oman

A study was undertaken in 2004 and 2005 to characterize pathogens associated with damping-off of greenhouse-grown cucumber seedlings in 13 districts in Oman. Identification of Pythium to the species level was based on sequences of the internal transcribed spacer (ITS) of the ribosomal DNA. Of the 98 Pythium isolates collected during the survey, Pythium aphanidermatum, P. spinosum, P. splendens and P. oligandrum accounted for 76%, 22%, 1% and 1%, respectively. Pythium aphanidermatum was isolated from all of the districts, while P. spinosum was isolated from seven districts. Pathogenicity tests showed inter- and intraspecific variation in aggressiveness between Pythium species. Pythium aphanidermatum, P. spinosum and P. splendens were found to be highly aggressive at 25°C. However, the aggressiveness of P. spinosum decreased when the temperature was raised to 30°C, which was found to correspond to the lower frequency of isolation of P. spinosum in the warmer seasons, compared to the cooler time of the year. Pythium aphanidermatum exhibited limited intraspecific variation in the sequences of the ITS region of the rDNA and showed 100% similarity to the corresponding P. aphanidermatum sequences from GenBank. The ITS sequence data, as well as morphological characteristics of P. spinosum isolates, showed a high level of similarity within and between P. spinosum and P. kunmingense, and suggested that the two species were synonymous. This study represents the first report of P. spinosum, P. splendens and P. oligandrum in Oman.

The physiological and behavioral responses of steers to gaseous ammonia in simulated long distance transport by ship.

Ammonia (NH3) can accumulate in high density cattle accommodation during live export shipments and could potentially threaten the animals' health and welfare. The effects of 4 NH3 concentrations, control (<8), 15, 30, and 45 ppm, on the physiology and behavior of steers were recorded. The animals were held for 12 d under a micro-climate and stocking density similar to shipboard conditions experienced on voyages from Australia to the Middle East during the northern hemispheric summer. In bronchoalveolar lavage samples, ammonia increased (P < 0.05) macrophage activity in proportion to NH3 concentration and it increased (P < 0.05) neutrophil percentage at 30 and 45 ppm, indicating active pulmonary inflammation. It also increased (P < 0.05) lacrimation, nasal secretions and coughing, particularly at 45 ppm, indicating that the NH3 was irritating the mucous membranes of the eyes, nasal cavity and respiratory tract. Ammonia had no effect (P > 0.05) on hematological parameters or body weight. Twenty-eight days after exposure to NH3, the steers' pulmonary macrophage activity and neutrophil levels had returned to normal. It was concluded that ammonia concentrations of 30 and 45 ppm induced temporary inflammatory responses which indicate an adverse effect on the welfare of steers.

Efficacy of fungicides against damping-off in papaya seedlings caused by Pythium aphanidermatum.

Various chemical and non-chemical treatments were tested for their efficacy against damping-off in papaya seedlings caused by Pythium aphanidermatum. Three-week-old papaya seedlings were placed in a climate controlled experimental chamber and inoculated with macerated mycelium of P. aphanidermatum. Propamocarb as Previcur was found to be most effective at managing damping-off in papaya seedlings.

Development of diagnotic capacity for Cotton Leaf Roll Virus from Thailand

Viral diseases of cotton are of economic significance in many parts of the world and several of these remain biosecurity threats to the Australian cotton industry, including Cotton Leaf Roll Virus (CLRV) from South East Asia. The proposed project will result in a greater understanding of the field symptoms of CLRV in Thailand and diagnostic assays used for its detection. I will also determine if the diagnostic assay being developed for Brazilian CLRDV as part of the CRDC project (11-12FRP00062) may also detect Thailand CLRV. It will provide educational opportunities to increase the knowledge base of staff currently working on cotton virus research and in doing so help to protect the Australian cotton industry from incursions of exotic viruses.