Galling problems – the Fergusobia nematode/Fergusonina fly mutualism on Myrtaceous hosts

Authors: DAVIES, K. - University Of Adelaide; YE, W. - North Carolina Department Of Agriculture; TAYLOR, G. - University Of Adelaide; Scheffer, Sonja; GIBLIN DAVIS, ROBIN - University Of Florida

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2016
Publication Date: 6/22/2016
Citation: Davies, K.A., Ye, W., Taylor, G.S., Scheffer, S.J., Giblin Davis, R. 2016. Galling problems – the Fergusobia nematode/Fergusonina fly mutualism on Myrtaceous hosts. Journal of Nematology. 18:629-649.

Interpretive Summary: Damage and disease caused by parasitic nematode worms make them one of the most important groups affecting animal and plant health. Losses to U.S. agriculture from nematode attack of crop plants exceed millions of dollars annually. However, nematodes that attack insects are important biological control agents for reducing insect pests of various crops. This manuscript reviews recent research on Fergusobia nematodes, a group that feeds on plants in the Myrtaceae (eucalyptus family). These nematodes also have an insect-parasitic life stage not seen in other plant-feeding nematodes. New data on the plants and the nematodes are provided in order to further clarify host relationships and evolutionary history. Results from this research will be of interest to nematologists, entomologists, ecologists, and evolutionary biologists.

Technical Abstract: Fergusobia (Sphaerularioidea, Tylenchidae) is the only known nematode to have a dicyclic life cycle with a generation in a plant (a myrtaceous host) followed by one in an insect (a Fergusonina fly). The nematode and fly have a mutualistic association, with the nematode inducing a plant gall on which the fly feeds and develops, and the fly providing transport for the nematode. The life cycle, specificity, diversity and distribution of the nematode are described, and the nematode phylogeny is discussed. Fergusobia is monophyletic, but its origins are unclear. This paper raises questions about Fergusobia, including: what model best accounts for evolution of the known diversity of the nematode/fly mutualism; how are the nematode/fly life cycles co-ordinated; how do the nematodes avoid resistance mechanisms of both flies and plants; what cecidogenic processes does the nematode use; and what is the form of parthenogenesis occurring in Fergusobia and how does it relate to the inheritance of variability? Given the models of genomes and trascriptomes now available for other plant parasitic nematodes, and the availability of technologies to examine Fergusobia, it should now be possible to answer some of these questions, and to begin to understand how Fergusobia nematodes might have evolved.