Differential responses to plant-feeding nematodes among sibling cultivars of dessert bananas (Cavendish subgroup) and a synthetic hybrid

All bananas cultivated for export are Cavendish cultivars and are considered to be very susceptible to both the burrowing nematode Radopholus similis and the lesion nematode Pratylenchus coffeae. Twelve cultivars of Musa spp. genome AAA cv. Grande Naine from mass field selections in Martinique and Guadeloupe were cloned and micro-propagated in tissue culture. Resistance of these sibling cultivars to nematodes was tested in two growth chamber trials and in one 2-year field trial in a former banana field heavily infested with nematodes and without control methods (no guying or nematicide applications). The field trial also included a new synthetic hybrid FB920 that has tolerance to yellow and black Sigatoka and partial resistance to nematodes. Trends were similar in growth chamber and field trials in that all Cavendish cultivars were susceptible to nematode species, although some differences in susceptibility were detected, and in particular roots of the selected cultivar MA13 contained fewer R. similis than the most susceptible cultivars of Cavendish (cvs. Petite naine, Poyo and L93). Cultivar MA13 was also less susceptible than most commercial cultivars to P. coffeae in the growth chamber trials, and a similar but insignificant trend was documented in the field trial. In the field trial, all cultivars experienced severe damage (lengthening of vegetative and reproductive stages, uprooting and reduced yield), which was attributed to the high level of nematode infestation. Although tolerance to nematodes in the field trial was greater for the synthetic new hybrid FB920 than for the Cavendish cultivars, FB920 produces small bunches and tall plants that will prevent its development as a banana for export (but will not prevent its production by small holders). In summary, this study shows that there is useful variation in tolerance to R. similis and P. coffeae among sibling Cavendish cultivars and that growth chamber trials with in vitrocultivated plants are useful for screening for such susceptibility. (Résumé d'auteur