Interactions of plant-parasitic nematodes and plant-pathogenic bacteria

Abstract

The number of complex associations between plant-parasitic nematodes and pathogenic bacteria in causing plant diseases has been demonstrated in last seven decades. The role of nematodes in these interactions is complex, and each disease complex is distinct from another and largely dependent on the type of nematode parasitism involved. Nematodes greatly increase development of plant disease caused by bacteria. Nematodes participate in disease complexes in different ways such as (1) predisposing agent, (2) increasing susceptibility of host by modifying physiology of host tissues, (3) breaking host resistance to bacterial pathogens, (4) acting as vectors of bacterial pathogens, and (5) changing the rhizosphere microflora. Generally, in nematode-bacterium disease complexes, the nematode becomes established more readily in the presence of bacterium, but at the later stage of infection, nematode suffers some inhibition. Moreover, prior occupancy of host tissues by nematode or bacterium has different influence on the disease severity. Sometimes, the presence of both the nematode and the bacterial pathogen is necessary for production of certain types of symptoms; for example, interaction of Aphelenchoides fragariae, or A. fragariae, and Corynebacterium fascians is necessary to produce cauliflower disease of strawberry while neither pathogen inoculated separately reproduced the disease. The disease complexes involving plant-parasitic nematodes and pathogenic bacteria have major economic hazards. Therefore, improved understanding of relationship between nematodes and bacteria is needed to control plant disease complexes and the damage caused by them.