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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Publications at this Location » Publication #347063

Research Project: Development of Knowledge-based Approaches for Disease Management in Small Fruit and Nursery Crops

Location: Horticultural Crops Disease and Pest Management Research Unit

Title: Variable abundance and distribution of Wolbachia and Cardinium Endosymbionts in plant-parasitic nematode field populations

item WASALA, S - Oregon State University
item BROWN, A - Texas Tech University
item KANG, JIWON - Oregon State University
item HOWE, D - Oregon State University
item Peetz, Amy
item Zasada, Inga
item DENVER, D - Oregon State University

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2019
Publication Date: 5/7/2019
Citation: Wasala, S.K., Brown, A.M., Kang, J., Howe, D.K., Peetz, A.B., Zasada, I.A., Denver, D.R. 2019. Variable abundance and distribution of Wolbachia and Cardinium Endosymbionts in plant-parasitic nematode field populations. Frontiers in Microbiology. 10:964.

Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause $100 billion dollars in global crop losses annually. There is a need to discover new ways to manage plant-parasitic nematodes. Endosymbionts, microbes that live within a host, have been shown to be targets for the management of insects and nematode parasites of humans. The focus of this research was the nematode endosymbiont Wolbachia. Populations of the plant-parasitic nematode Pratylenchus penetrans were collected from raspberry fields; this nematode is an important production-limiting pest in this crop. Collected nematodes were then screened to determine if Wolbachia was present. It was discovered that Wolbachia is not present in all populations. When it was found to be present a larger percentage of the population was female, compared to an equal percentage of males and females in populations without Wolbachia. These finding are significant because they indicate that Wolbachia is a reproductive manipulating endosymbiont in this nematode. This research will be used by scientist to continue to explore the role of Wolbachia in plant-parasitic nematodes and may lead to the development of novel management strategies to combat P. penetrans in raspberry and other crops.

Technical Abstract: Wolbachia is an endosymbiont that often acts as a reproductive parasite in arthropods and an obligate mutualist in filarial nematodes. Plant-parasitic nematodes host early-branching Wolbachia strains, but the phenotypic effects of these are unknown. We designed a polymerase chain reaction screen to assess prevalence of Wolbachia in males and females from ten P. penetrans populations and compared this with nematode sex ratios and genetic variation among populations. Our study identified Wolbachia in four of the ten P. penetrans populations investigated, including raspberry fields in Washington and a greenhouse population in Oregon, USA. Sequence analysis revealed that 45/54 individual nematodes shared a common Wolbachia 16S rRNA sequence, while variant sequences were observed, sometimes within a single nematode. Prevalence of Wolbachia ranged from 11% to 58% in infected populations, contrasting with the pattern in filarial nematodes (typically 100%). All infected populations had female-skewed sex ratios (up to 96%), with degree of skew correlating with Wolbachia prevalence. Together, absence of infection in some populations, multiple genetic variants within individuals, and correlation of female-bias with infection rate suggest this Wolbachia is not a mutualist, but instead may be a sex-ratio distorting reproductive parasite – a novel result with implications for future biological control.