Agronomy and Crop Science

ABSTRACT: The municipality of Ji-Paraná, Rondônia, is one of the major dairy production areas in the north region of Brazil. Thus, it is important to evaluate infectious agents that have the potential to negatively affect productivity in the industry. The objective of this study was to investigate the prevalence of ' Candidatus Mycoplasma haemobos' by using a PCR-based detection method and correlate this with dairy herd variables (abortion frequency, weak calf birth rate, total cattle number, >24-month-old cow number, farm size, and production system) in family farms of the Ji-Paraná municipality, north region, Brazil. Blood samples were collected from 320 dairy cows located across 64 farms (i.e., five animals per farm) from September 2012 to November 2013. Overall prevalence of 'Ca. M. haemobos' was 64.2% and prevalence per herd was 95.3%; the number of >24-month-old cows in the farms studied correlated with ' Ca. M. haemobos' infection rates. Considering the importance of the dairy industry to the study area, additional investigations are necessary to evaluate the effect of chronic infection in these animals on milk production and herd health.

Previous studies have shown that the fastidious bacterial plant pathogen ‘Candidatus Liberibacter solanacearum’ (CLso) is transmitted circulatively and propagatively by the potato psyllid (PoP) Bactericera cockerelli. In this study, the temporal and spatial interrelationships between CLso PoP were investigated by scanning electron microscopy of the digestive system of PoP immature and adult instars and salivary glands of adults post CLso ingestion. CLso biofilms were not detectable on the outer midgut surface of the first and second instars; however, for third to fifth instars and teneral and mature adults, biofilms were observed in increasing numbers in each successive developmental stage. In adult PoP midguts, CLso cells were observed between the basal lamina and basal epithelial cell membranes; in basal laminar perforations, on the outer basal laminar surface, and in the ventricular lumen, epithelial cytosol, and filter chamber periventricular space. CLso were also abundantly visible in the salivary gland pericellular spaces and in the epidermal cell cytosol of the head. Collectively, these results point to an intrusive, systemic invasion of PoP by CLso that employs an endo/exocytosis-like mechanism, in the context of a propagative, circulative mode of transmission.