The reproductive potential of the root-knot nematode Meloidogyne incognita is affected by selection for virulence against major resistance genes from tomato and pepper

Abstract

The emergence of virulent root-knot nematode populations, able to overcome the resistance conferred by some of the resistance genes (R-genes) in Solanaceous crops, i.e., Mi(s) in tomato, Me(s) in pepper, may constitute a severe limitation to their use in the field. Research has been conducted to evaluate the durability of these R-genes, by comparing the reproduction of several laboratory-selected and wild virulent Meloidogyne incognita isolates, on both susceptible and resistant tomatoes and peppers. We first show that the Me1 R-gene in pepper behaves as a robust R-gene controlling avirulent and virulent Me3, Me7 or Mi-1 isolates. Although the reproductive potential of the virulent isolates was highly variable on susceptible and resistant plants, we also confirm that virulence is highly specific to a determined Rgene on which selection has occurred. Another significant experimental result is the observation that a reproductive fitness cost is associated with nematode virulence against Mi-1 in tomato and Me3 and Me7 in pepper. The adaptative significance of trade-offs between selected characters and fitness-related traits, suggests that, although the resistance can be broken, it may be preserved in some conditions if the virulent nematodes are counter-selected in susceptible plants. All these results have important consequences for the management of plant resistance in the field.

Development of virulence to Meloidogyne incognita on resistant pepper rootstocks

“…Moreover, the response of the pepper cultivars carrying the gene Me3 seemed to depend on the Meloidogyne population. This was confirmed with several laboratory-selected and natural M. incognita virulent isolates (Djian-Caporalino et al, 2011).…”

“…Previous work by Castagnone-Sereno et al (2001) and Djian-Caporalino et al (2011) demonstrated that selection of virulence was highly specific, as naturally occurring and laboratory selected Mi-virulent nematodes to resistant tomato were unable to multiply on resistant peppers carrying the Me3 (= Me7) resistance gene and viceversa. The Me1 gene showed itself to be robust, as none of the virulent populations against Mi, and Me3 (= Me7) multiplied on peppers containing the Me1 resistance gene.…”

How Durable is Root Knot Nematode Resistance in Tomato?

“…The durability of resistance mostly depends upon the occurrence of virulence isolates of nematode. Djian-Caporalino et al (2011) reported that a propagative fitness cost is linked to nematode virulence against Mi-1 in tomato. Although the resistance is broken down, it may be conserved in some conditions if the virulent nematodes are counter-selected in susceptible plants (Djian-Caporalino et al 2011).…”

“…Djian-Caporalino et al (2011) reported that a propagative fitness cost is linked to nematode virulence against Mi-1 in tomato. Although the resistance is broken down, it may be conserved in some conditions if the virulent nematodes are counter-selected in susceptible plants (Djian-Caporalino et al 2011). Therefore, the durability should be assessed either by long-term cropping of resistant cultivars or by cultivating resistant cultivars under high inoculum pressure.…”

Role of phytohormones (indol acetic acid, jasmonic acid, salcylic acid, and ethylene) in nematode-plant interactions

“…Many studies showed that root knot nematode species (RKNs), which causes a major economic loss throughout the world, have very broad host ranges. Some other species of nematode are limited to one or a few hosts (Djian-Caporalino et al, 2011;Gleason et al, 2008). For example, cyst nematodes usually have narrower host ranges.…”