Red alert on the plant-parasitic nematodes of banana

A mutant of 'Grande Naine', the cultivar MAI3 (Mt/sa AAA, Cavendish subgroup) has been selected in the field in Martinique for its good horticultural characteristics (hardiness, bunch conformation, productivity...). This peculiar cultivar always demonstrated significant lower susceptibilities to the bUlTOwing nematode Radopholus similis and to the lesion nematode Pratylenchus coffeae. In addition, the cv MAl3 exhibited singularly redder pseudostem as compared to others Cavendish clones. On the basis ofthese observations, we selected in field conditions some others 'coloured' mutants among different banana subgroups; cv MAl3_Green (Musa AAA, Cavendish subgroup), cv dwarfMossi_Green (Musa AAA, Red subgroup) and cvs 920_Red, 920_Green and 921_Red (Musa AAA, CIRAD hybrids). The susceptibility to nematodes of classic cultivars and associated mutants was evaluated under controlled conditions in a growth chamber on Andosol (volcanic ash soils representative of the French West Indies banana production area), at 24-28°C and 80% RH. Forty-five days after inoculation of each banana clone with 400 R. similis or P. coffeae per plant, the entire root system was carefully collected and weighted, and nematodes were extracted. In vitro micropropagation has no effect on the colour stability of the pseudostem. Reproductive factors and root infestations showed consistent trends, with an increase in R. similis root infestations for green mutants (up to 54%) and a decrease for red mutants (up to 61%) compared to classic cultivars. Surprisingly, the opposite consistent trend was observed for P. coffeae root infestations, with a decrease for green mutants (up to 43%) and an increase for red mutants (up to 76%) compared to classic cultivars. These results provide first evidence that colour criterion, representative of the anthocyanins content, could be a good and fairly simple indicator of nematode susceptibility in selection process. (Texte intégral