Résumé
► While crop mixtures are used against airborne diseases, there is scarce data for soil borne pests. ► Banana mixtures had significant effect on plant-feeding nematode populations. ► Mixing the more and less tolerant cultivars leads to an intermediate level of nematode populations.
Varietal mixture is a cultural technique in which the genetic and functional diversities of varieties are used to manage pests and diseases. This strategy is commonly used on grass crops such as rice, barley, maize, and wheat to mitigate some windborne and soilborne pathogens. The effects of varietal mixtures on the number and community structure of pests, including plant-feeding nematodes (PFNs), however, have rarely been studied. In experiments conducted in Martinique, we evaluated the effect of varietal mixtures of bananas on PFN communities. A growth chamber experiment was used to measure the susceptibility of three banana cultivars dessert banana cv. 902 (
Musa AAA, Cavendish subgroup); a new synthetic hybrid cv. FB924 (
Musa AAA); and a plantain cv. Creole blanche (
Musa AAB, French Horn) to the two major PFNs. The multiplication rates of
Radopholus similis and
Pratylenchus coffeae were substantially different on the three varieties; for example, the multiplication rate was up to 10 times greater on plantain cv. Creole blanche than on hybrid cv. FB924. In a field experiment, we planted the three varieties in pairs that included all six possible combinations. Banana varietal mixtures significantly affected both PFN densities and community composition. Differences in community composition among the pairs involved a shifting equilibrium among nematode species and an interspecific competition for food resources. The relative abundance of the spiral nematode
Helicotylenchus multicinctus increased while that of the burrowing nematode
R. similis, which is the most damaging species on bananas, decreased. The use of a varietal mixture in which one variety supports a low PFN multiplication rate appears to have practical relevance, especially in systems based on very susceptible cultivars such as plantains. The use of varietal mixtures should not create management problems, especially for plantations that produce bananas for local markets.