Requirement of field pea for inoculation with Rhizobium and lime pelleting in soils of Western Australia

The requirement of field pea (Pisum sativum) for seed inoculation with Rhizobium and for lime pelleting of inoculated seed was investigated in field experiments in the south-west of Western Australia, especially at locations where inoculated field pea had been grown 2 years previously. At most sites with previous pea cropping, the nodulation, total dry matter and nitrogen, and grain yield of pea were not improved by seed inoculation or lime pelleting. At these sites soil populations of R. leguminosarum by. viciae at sowing were >103/g soil. Responses to inoculation were measured at sites where the soil was very acidic [pH(CaCl2) <4.5], or mildly acidic (to pH 4.9) and of light texture (>90% sand + gravel), or where pea had not grown previously. There were fewer rhizobia at sowing at these locations. Lime pelleting was not generally required to maximise field pea growth or yield, but yield was affected by the inoculant Rhizobium strain.

A serological and virological survey for evidence of infection with Newcastle disease virus in Australian chicken farms

OBJECTIVE

To determine the prevalence and distribution of antibodies to Newcastle disease virus on Australian chicken farms and to determine the pathotype and relationships of the Newcastle disease viruses present on those farms.

DESIGN

A cross-sectional survey of 753 commercial chicken farms.

PROCEDURE

The survey comprised a detailed questionnaire and collection of venous blood samples. The titre of antibodies to Newcastle disease virus was determined by haemagglutination inhibition. Virus isolation was conducted from cloacal and tracheal swabs taken from chickens in serologically positive flocks. Virus isolates were pathotyped on the basis of the deduced Fusion protein cleavage site determined by nucleotide sequencing of a 265 bp region of the genome in the region of the cleavage site.

RESULTS

Antibody evidence of Newcastle disease virus infection was found on 300 of the 753 surveyed farms throughout all 11 geographic regions of the survey. The highest prevalence occurred in the Sydney basin, New South Wales and Victoria east regions. Antibody titres were also highest in the regions where serologically positive flocks were most prevalent. The 259 virus isolates revealed nine different RNA sequences. Of the nine virus groups isolated, the most common group W was identical in sequence to the V4 vaccine strain. Five of the other groups had novel RNA sequences in the region of the F protein cleavage site.

CONCLUSIONS

Antibodies to Newcastle disease virus are highly prevalent in the Australian chicken flock but all identified strains were avirulent in nature.