Attraction and penetration of Musa by the burrowing nematode, Radopholus similis, in an autotrophic bipartite culture system

Abstract

Summary Our objective was to discover the stages (pre- or post-infection) in which the resistance to burrowing nematode (Radopholus similis) occurs in two resistant banana (Musa spp.) cultivars. An autotrophic in vitro culture system was used to compare R. similis migration towards, and penetration into, the banana roots. A new two-compartment autotrophic in vitro model system was developed using agar-based medium to examine the migration of R. similis to either the susceptible ‘Grande Naine’ or the resistant ‘Yangambi km5’ (‘Ykm5’), when both the Musa genotypes were present at equal distance. The autotrophic in vitro model system was advantageous, because it supported continuous root growth due to the actively photosynthesising shoots growing in the open air, while the in vitro root conditions make it possible to observe and assess the nematode chemotaxis in the transparent medium. Significantly fewer nematodes migrated towards the resistant ‘Ykm5’ plants when compared to both the susceptible ‘Grande Naine’, and another resistant cultivar, ‘Saba’, at 1 h after infection. This signals a possibility of a lower concentration or different composition of nematode attractants in ‘Ykm5’ root exudates. No significant differences were observed in the percentage of R. similis that migrated towards the roots of the susceptible and resistant banana plants at 3, 4 and 6 h after inoculation. No significant differences were observed in the percentages of female penetration in the resistant and susceptible plant roots at 1 and 2 days after inoculation. The results of the two-compartment system confirmed that when a choice is given to migrate towards the resistant and susceptible genotypes, no differences were observed in the percentage of female migration towards both the genotypes.