Genomic Analysis of the Root-Knot Nematode Genome

Abstract

Plant-parasitic nematodes cause substantial agricultural damage throughout the world, triggering as much as $100 billion in economic losses per year. Measures to control these pests are limited and include the use of agrichemi-cals such as methyl bromide (now available only on a “critical use exemption” basis) or the planting of crops that have natural resistance. However, the availability of chemical pesticides is decreasing and host resistance is limited. A better understanding of the complex interaction between plant-parasitic nematodes and their hosts is needed to develop new control strategies (including new chemicals). The vast majority of the damage is caused by sedentary endoparasitic forms in the order Tylenchida, which fall into clade IV of the Nematoda (Blaxter et al. 1998). In particular, the root-knot nematodes ( Meloidogyne spp.), soybean cyst nematodes ( Heterodera glycines ), and potato cyst ( Globodera spp.) nematodes are devastating parasites of plant roots.In this chapter, we will present a brief overview of the status of genomic research on root-knot nematodes. Root-knot nematodes, in particular M. hapla, are emerging as a model species for research on sedentary endoparasites. We will discuss the impact of root-knot nematodes on the host plant and focus on genomic approaches to unraveling the complex nature of the interaction from the nematode's perspective. In addition to the complete genome sequence of M. hapla, a complete genome sequence has simultaneously been obtained for the aneuploid species, M. incognita (Abad, personal communication). In the future, comparison between these two genomes will provide fundamental clues as to the evolution and biology of root-knot nematodes.